avprobe - avprobe media prober avprobe [options] [ input_file] avprobe gathers information from multimedia streams and prints it in human- and machine-readable fashion. For example it can be used to check the format of the container used by a multimedia stream and the format and type of each media stream contained in it. If a filename is specified in input, avprobe will try to open and probe the file content. If the file cannot be opened or recognized as a multimedia file, a positive exit code is returned. avprobe may be employed both as a standalone application or in combination with a textual filter, which may perform more sophisticated processing, e.g. statistical processing or plotting. Options are used to list some of the formats supported by avprobe or for specifying which information to display, and for setting how avprobe will show it. avprobe output is designed to be easily parsable by any INI or JSON parsers. All the numerical options, if not specified otherwise, accept in input a string representing a number, which may contain one of the SI unit prefixes, for example 'K', 'M', 'G'. If 'i' is appended after the prefix, binary prefixes are used, which are based on powers of 1024 instead of powers of 1000. The 'B' postfix multiplies the value by 8, and can be appended after a unit prefix or used alone. This allows using for example 'KB', 'MiB', 'G' and 'B' as number postfix. Options which do not take arguments are boolean options, and set the corresponding value to true. They can be set to false by prefixing with "no" the option name, for example using "-nofoo" in the command line will set to false the boolean option with name "foo".

Stream specifiers¶

Some options are applied per-stream, e.g. bitrate or codec. Stream specifiers are used to precisely specify which stream(s) does a given option belong to. A stream specifier is a string generally appended to the option name and separated from it by a colon. E.g. "-codec:a:1 ac3" option contains "a:1" stream specifer, which matches the second audio stream. Therefore it would select the ac3 codec for the second audio stream. A stream specifier can match several stream, the option is then applied to all of them. E.g. the stream specifier in "-b:a 128k" matches all audio streams. An empty stream specifier matches all streams, for example "-codec copy" or "-codec: copy" would copy all the streams without reencoding. Possible forms of stream specifiers are:

stream_index

Matches the stream with this index. E.g. "-threads:1 4" would set the thread count for the second stream to 4.

stream_type[:stream_index]

stream_type is one of: 'v' for video, 'a' for audio, 's' for subtitle, 'd' for data and 't' for attachments. If stream_index is given, then matches stream number stream_index of this type. Otherwise matches all streams of this type.

p:program_id[:stream_index]

If stream_index is given, then matches stream number stream_index in program with id program_id. Otherwise matches all streams in this program.

i:stream_id

Match the stream by stream id (e.g. PID in MPEG-TS container).

m:key[:value]

Matches streams with the metadata tag key having the specified value. If value is not given, matches streams that contain the given tag with any value.

Note that in avconv, matching by metadata will only work properly for input files.

Generic options¶

These options are shared amongst the av* tools.

-L

Show license.

-h, -?, -help, --help [arg]

Show help. An optional parameter may be specified to print help about a specific item.

Possible values of arg are:

-version

Show version.

-formats

Show available formats.

The fields preceding the format names have the following meanings:

-codecs

Show all codecs known to libavcodec.

Note that the term 'codec' is used throughout this documentation as a shortcut for what is more correctly called a media bitstream format.

-decoders

Show available decoders.

-encoders

Show all available encoders.

-bsfs

Show available bitstream filters.

-protocols

Show available protocols.

-filters

Show available libavfilter filters.

-pix_fmts

Show available pixel formats.

-sample_fmts

Show available sample formats.

-loglevel loglevel | -v loglevel

Set the logging level used by the library. loglevel is a number or a string containing one of the following values:

-cpuflags mask (global)

Set a mask that's applied to autodetected CPU flags. This option is intended for testing. Do not use it unless you know what you're doing.

AVOptions¶

These options are provided directly by the libavformat, libavdevice and libavcodec libraries. To see the list of available AVOptions, use the -help option. They are separated into two categories:

generic

These options can be set for any container, codec or device. Generic options are listed under AVFormatContext options for containers/devices and under AVCodecContext options for codecs.

private

These options are specific to the given container, device or codec. Private options are listed under their corresponding containers/devices/codecs.

For example to write an ID3v2.3 header instead of a default ID3v2.4 to an MP3 file, use the id3v2_version private option of the MP3 muxer:

        avconv -i input.flac -id3v2_version 3 out.mp3

All codec AVOptions are obviously per-stream, so the chapter on stream specifiers applies to them Note -nooption syntax cannot be used for boolean AVOptions, use -option 0/ -option 1. Note2 old undocumented way of specifying per-stream AVOptions by prepending v/a/s to the options name is now obsolete and will be removed soon.

Codec AVOptions¶

-b[:stream_specifier] integer (output,audio,video )

set bitrate (in bits/s)

-bt[:stream_specifier] integer (output,video)

Set video bitrate tolerance (in bits/s). In 1-pass mode, bitrate tolerance specifies how far ratecontrol is willing to deviate from the target average bitrate value. This is not related to minimum/maximum bitrate. Lowering tolerance too much has an adverse effect on quality.

-flags[:stream_specifier] flags (input/output,audio,video )

Possible values:

-me_method[:stream_specifier] integer (output,video )

set motion estimation method

Possible values:

-g[:stream_specifier] integer (output,video)

set the group of picture (GOP) size

-ar[:stream_specifier] integer (input/output,audio )

set audio sampling rate (in Hz)

-ac[:stream_specifier] integer (input/output,audio )

set number of audio channels

-cutoff[:stream_specifier] integer (output,audio )

set cutoff bandwidth

-frame_size[:stream_specifier] integer (output,audio )

-qcomp[:stream_specifier] float (output,video)

video quantizer scale compression (VBR). Constant of ratecontrol equation. Recommended range for default rc_eq: 0.0-1.0

-qblur[:stream_specifier] float (output,video)

video quantizer scale blur (VBR)

-qmin[:stream_specifier] integer (output,video)

minimum video quantizer scale (VBR)

-qmax[:stream_specifier] integer (output,video)

maximum video quantizer scale (VBR)

-qdiff[:stream_specifier] integer (output,video )

maximum difference between the quantizer scales (VBR)

-bf[:stream_specifier] integer (output,video)

use 'frames' B frames

-b_qfactor[:stream_specifier] float (output,video )

QP factor between P- and B-frames

-rc_strategy[:stream_specifier] integer (output,video )

ratecontrol method

-b_strategy[:stream_specifier] integer (output,video )

strategy to choose between I/P/B-frames

-ps[:stream_specifier] integer (output,video)

RTP payload size in bytes

-bug[:stream_specifier] flags (input,video)

work around not autodetected encoder bugs

Possible values:

-strict[:stream_specifier] integer (input/output,audio,video )

how strictly to follow the standards

Possible values:

-b_qoffset[:stream_specifier] float (output,video )

QP offset between P- and B-frames

-err_detect[:stream_specifier] flags (input,audio,video )

set error detection flags

Possible values:

-mpeg_quant[:stream_specifier] integer (output,video )

use MPEG quantizers instead of H.263

-qsquish[:stream_specifier] float (output,video )

how to keep quantizer between qmin and qmax (0 = clip, 1 = use differentiable function)

-rc_qmod_amp[:stream_specifier] float (output,video )

experimental quantizer modulation

-rc_qmod_freq[:stream_specifier] integer (output,video )

experimental quantizer modulation

-rc_eq[:stream_specifier] string (output,video)

Set rate control equation. When computing the expression, besides the standard functions defined in the section 'Expression Evaluation', the following functions are available: bits2qp(bits), qp2bits(qp). Also the following constants are available: iTex pTex tex mv fCode iCount mcVar var isI isP isB avgQP qComp avgIITex avgPITex avgPPTex avgBPTex avgTex.

-maxrate[:stream_specifier] integer (output,audio,video )

Set maximum bitrate tolerance (in bits/s). Requires bufsize to be set.

-minrate[:stream_specifier] integer (output,audio,video )

Set minimum bitrate tolerance (in bits/s). Most useful in setting up a CBR encode. It is of little use otherwise.

-bufsize[:stream_specifier] integer (output,audio,video )

set ratecontrol buffer size (in bits)

-rc_buf_aggressivity[:stream_specifier] float (output,video )

currently useless

-i_qfactor[:stream_specifier] float (output,video )

QP factor between P- and I-frames

-i_qoffset[:stream_specifier] float (output,video )

QP offset between P- and I-frames

-rc_init_cplx[:stream_specifier] float (output,video )

initial complexity for 1-pass encoding

-dct[:stream_specifier] integer (output,video)

DCT algorithm

Possible values:

-lumi_mask[:stream_specifier] float (output,video )

compresses bright areas stronger than medium ones

-tcplx_mask[:stream_specifier] float (output,video )

temporal complexity masking

-scplx_mask[:stream_specifier] float (output,video )

spatial complexity masking

-p_mask[:stream_specifier] float (output,video)

inter masking

-dark_mask[:stream_specifier] float (output,video )

compresses dark areas stronger than medium ones

-idct[:stream_specifier] integer (input/output,video )

select IDCT implementation

Possible values:

-ec[:stream_specifier] flags (input,video)

set error concealment strategy

Possible values:

-pred[:stream_specifier] integer (output,video)

prediction method

Possible values:

-aspect[:stream_specifier] rational number (output,video )

sample aspect ratio

-debug[:stream_specifier] flags (input/output,audio,video,subtitles )

print specific debug info

Possible values:

-vismv[:stream_specifier] integer (input,video)

visualize motion vectors (MVs)

Possible values:

-cmp[:stream_specifier] integer (output,video)

full-pel ME compare function

Possible values:

-subcmp[:stream_specifier] integer (output,video )

sub-pel ME compare function

Possible values:

-mbcmp[:stream_specifier] integer (output,video )

macroblock compare function

Possible values:

-ildctcmp[:stream_specifier] integer (output,video )

interlaced DCT compare function

Possible values:

-dia_size[:stream_specifier] integer (output,video )

diamond type & size for motion estimation

-last_pred[:stream_specifier] integer (output,video )

amount of motion predictors from the previous frame

-preme[:stream_specifier] integer (output,video )

pre motion estimation

-precmp[:stream_specifier] integer (output,video )

pre motion estimation compare function

Possible values:

-pre_dia_size[:stream_specifier] integer (output,video )

diamond type & size for motion estimation pre-pass

-subq[:stream_specifier] integer (output,video)

sub-pel motion estimation quality

-me_range[:stream_specifier] integer (output,video )

limit motion vectors range (1023 for DivX player)

-ibias[:stream_specifier] integer (output,video )

intra quant bias

-pbias[:stream_specifier] integer (output,video )

inter quant bias

-global_quality[:stream_specifier] integer (output,audio,video )

-coder[:stream_specifier] integer (output,video )

Possible values:

-context[:stream_specifier] integer (output,video )

context model

-mbd[:stream_specifier] integer (output,video)

macroblock decision algorithm (high quality mode)

Possible values:

-sc_threshold[:stream_specifier] integer (output,video )

scene change threshold

-lmin[:stream_specifier] integer (output,video)

minimum Lagrange factor (VBR)

-lmax[:stream_specifier] integer (output,video)

maximum Lagrange factor (VBR)

-nr[:stream_specifier] integer (output,video)

noise reduction

-rc_init_occupancy[:stream_specifier] integer (output,video )

number of bits which should be loaded into the rc buffer before decoding starts

-flags2[:stream_specifier] flags (input/output,audio,video )

Possible values:

-error[:stream_specifier] integer (output,video )

-threads[:stream_specifier] integer (input/output,video )

Possible values:

-me_threshold[:stream_specifier] integer (output,video )

motion estimation threshold

-mb_threshold[:stream_specifier] integer (output,video )

macroblock threshold

-dc[:stream_specifier] integer (output,video)

intra_dc_precision

-nssew[:stream_specifier] integer (output,video )

nsse weight

-skip_top[:stream_specifier] integer (input,video )

number of macroblock rows at the top which are skipped

-skip_bottom[:stream_specifier] integer (input,video )

number of macroblock rows at the bottom which are skipped

-profile[:stream_specifier] integer (output,audio,video )

Possible values:

-level[:stream_specifier] integer (output,audio,video )

Possible values:

-skip_threshold[:stream_specifier] integer (output,video )

frame skip threshold

-skip_factor[:stream_specifier] integer (output,video )

frame skip factor

-skip_exp[:stream_specifier] integer (output,video )

frame skip exponent

-skipcmp[:stream_specifier] integer (output,video )

frame skip compare function

Possible values:

-border_mask[:stream_specifier] float (output,video )

increase the quantizer for macroblocks close to borders

-mblmin[:stream_specifier] integer (output,video )

minimum macroblock Lagrange factor (VBR)

-mblmax[:stream_specifier] integer (output,video )

maximum macroblock Lagrange factor (VBR)

-mepc[:stream_specifier] integer (output,video)

motion estimation bitrate penalty compensation (1.0 = 256)

-skip_loop_filter[:stream_specifier] integer (input,video )

Possible values:

-skip_idct[:stream_specifier] integer (input,video )

Possible values:

-skip_frame[:stream_specifier] integer (input,video )

Possible values:

-bidir_refine[:stream_specifier] integer (output,video )

refine the two motion vectors used in bidirectional macroblocks

-brd_scale[:stream_specifier] integer (output,video )

downscale frames for dynamic B-frame decision

-keyint_min[:stream_specifier] integer (output,video )

minimum interval between IDR-frames (x264)

-refs[:stream_specifier] integer (output,video)

reference frames to consider for motion compensation

-chromaoffset[:stream_specifier] integer (output,video )

chroma QP offset from luma

-trellis[:stream_specifier] integer (output,audio,video )

rate-distortion optimal quantization

-sc_factor[:stream_specifier] integer (output,video )

multiplied by qscale for each frame and added to scene_change_score

-mv0_threshold[:stream_specifier] integer (output,video )

-b_sensitivity[:stream_specifier] integer (output,video )

adjust sensitivity of b_frame_strategy 1

-compression_level[:stream_specifier] integer (output,audio,video )

-min_prediction_order[:stream_specifier] integer (output,audio )

-max_prediction_order[:stream_specifier] integer (output,audio )

-timecode_frame_start[:stream_specifier] integer (output,video )

GOP timecode frame start number, in non-drop-frame format

-request_channels[:stream_specifier] integer (input,audio )

set desired number of audio channels

-channel_layout[:stream_specifier] integer (input/output,audio )

Possible values:

-request_channel_layout[:stream_specifier] integer (input,audio)

Possible values:

-rc_max_vbv_use[:stream_specifier] float (output,video )

-rc_min_vbv_use[:stream_specifier] float (output,video )

-ticks_per_frame[:stream_specifier] integer (input/output,audio,video )

-color_primaries[:stream_specifier] integer (input/output,video )

color primaries

Possible values:

-color_trc[:stream_specifier] integer (input/output,video )

color transfert characteristic

Possible values:

-colorspace[:stream_specifier] integer (input/output,video )

colorspace

Possible values:

-color_range[:stream_specifier] integer (input/output,video )

color range

Possible values:

-chroma_sample_location[:stream_specifier] integer (input/output,video)

-slices[:stream_specifier] integer (output,video )

number of slices, used in parallelized encoding

-thread_type[:stream_specifier] flags (input/output,video )

select multithreading type

Possible values:

-audio_service_type[:stream_specifier] integer (output,audio )

audio service type

Possible values:

-request_sample_fmt[:stream_specifier] integer (input,audio )

Possible values:

-refcounted_frames[:stream_specifier] integer (input,audio,video )

-side_data_only_packets[:stream_specifier] integer (output,audio,video)

Format AVOptions¶

-probesize integer (input)

set probing size

-packetsize integer (output)

set packet size

-fflags flags (input/output)

Possible values:

-analyzeduration integer (input)

how many microseconds are analyzed to estimate duration

-cryptokey hexadecimal string (input)

decryption key

-indexmem integer (input)

max memory used for timestamp index (per stream)

-rtbufsize integer (input)

max memory used for buffering real-time frames

-fdebug flags (input/output)

print specific debug info

Possible values:

-max_delay integer (input/output)

maximum muxing or demuxing delay in microseconds

-fpsprobesize integer (input)

number of frames used to probe fps

-f_err_detect flags (input)

set error detection flags (deprecated; use err_detect, save via avconv)

Possible values:

-err_detect flags (input)

set error detection flags

Possible values:

-max_interleave_delta integer (output)

maximum buffering duration for interleaving

-f_strict integer (input/output)

how strictly to follow the standards (deprecated; use strict, save via avconv)

Possible values:

-strict integer (input/output)

how strictly to follow the standards

Possible values:

Main options¶

-f format

Force format to use.

-of formatter

Use a specific formatter to output the document. The following formatters are available

-unit

Show the unit of the displayed values.

-prefix

Use SI prefixes for the displayed values. Unless the "-byte_binary_prefix" option is used all the prefixes are decimal.

-byte_binary_prefix

Force the use of binary prefixes for byte values.

-sexagesimal

Use sexagesimal format HH:MM:SS.MICROSECONDS for time values.

-pretty

Prettify the format of the displayed values, it corresponds to the options "-unit -prefix -byte_binary_prefix -sexagesimal".

-show_format

Show information about the container format of the input multimedia stream.

All the container format information is printed within a section with name "FORMAT".

-show_format_entry name

Like -show_format, but only prints the specified entry of the container format information, rather than all. This option may be given more than once, then all specified entries will be shown.

-show_packets

Show information about each packet contained in the input multimedia stream.

The information for each single packet is printed within a dedicated section with name "PACKET".

-show_streams

Show information about each media stream contained in the input multimedia stream.

Each media stream information is printed within a dedicated section with name "STREAM".

Demuxers are configured elements in Libav which allow to read the multimedia streams from a particular type of file. When you configure your Libav build, all the supported demuxers are enabled by default. You can list all available ones using the configure option "--list-demuxers". You can disable all the demuxers using the configure option "--disable-demuxers", and selectively enable a single demuxer with the option "--enable-demuxer= DEMUXER", or disable it with the option "--disable-demuxer= DEMUXER". The option "-formats" of the av* tools will display the list of enabled demuxers. The description of some of the currently available demuxers follows.

image2¶

Image file demuxer. This demuxer reads from a list of image files specified by a pattern. The pattern may contain the string "%d" or "%0 Nd", which specifies the position of the characters representing a sequential number in each filename matched by the pattern. If the form "%d0 Nd" is used, the string representing the number in each filename is 0-padded and N is the total number of 0-padded digits representing the number. The literal character '%' can be specified in the pattern with the string "%%". If the pattern contains "%d" or "%0 Nd", the first filename of the file list specified by the pattern must contain a number inclusively contained between 0 and 4, all the following numbers must be sequential. This limitation may be hopefully fixed. The pattern may contain a suffix which is used to automatically determine the format of the images contained in the files. For example the pattern "img-%03d.bmp" will match a sequence of filenames of the form img-001.bmp, img-002.bmp, ..., img-010.bmp, etc.; the pattern "i%%m%%g-%d.jpg" will match a sequence of filenames of the form i%m%g-1.jpg, i%m%g-2.jpg, ..., i%m%g-10.jpg, etc. The size, the pixel format, and the format of each image must be the same for all the files in the sequence. The following example shows how to use avconv for creating a video from the images in the file sequence img-001.jpeg, img-002.jpeg, ..., assuming an input framerate of 10 frames per second:

        avconv -i 'img-%03d.jpeg' -r 10 out.mkv

Note that the pattern must not necessarily contain "%d" or "%0 Nd", for example to convert a single image file img.jpeg you can employ the command:

        avconv -i img.jpeg img.png

-pixel_format format

Set the pixel format (for raw image)

-video_size size

Set the frame size (for raw image)

-framerate rate

Set the frame rate

-loop bool

Loop over the images

-start_number start

Specify the first number in the sequence

applehttp¶

Apple HTTP Live Streaming demuxer. This demuxer presents all AVStreams from all variant streams. The id field is set to the bitrate variant index number. By setting the discard flags on AVStreams (by pressing 'a' or 'v' in avplay), the caller can decide which variant streams to actually receive. The total bitrate of the variant that the stream belongs to is available in a metadata key named "variant_bitrate".

flv¶

Adobe Flash Video Format demuxer. This demuxer is used to demux FLV files and RTMP network streams.

-flv_metadata bool

Allocate the streams according to the onMetaData array content.

asf¶

Advanced Systems Format demuxer. This demuxer is used to demux ASF files and MMS network streams.

-no_resync_search bool

Do not try to resynchronize by looking for a certain optional start code.

Muxers are configured elements in Libav which allow writing multimedia streams to a particular type of file. When you configure your Libav build, all the supported muxers are enabled by default. You can list all available muxers using the configure option "--list-muxers". You can disable all the muxers with the configure option "--disable-muxers" and selectively enable / disable single muxers with the options "--enable-muxer= MUXER" / "--disable-muxer= MUXER". The option "-formats" of the av* tools will display the list of enabled muxers. A description of some of the currently available muxers follows.

crc¶

CRC (Cyclic Redundancy Check) testing format. This muxer computes and prints the Adler-32 CRC of all the input audio and video frames. By default audio frames are converted to signed 16-bit raw audio and video frames to raw video before computing the CRC. The output of the muxer consists of a single line of the form: CRC=0x CRC, where CRC is a hexadecimal number 0-padded to 8 digits containing the CRC for all the decoded input frames. For example to compute the CRC of the input, and store it in the file out.crc:

        avconv -i INPUT -f crc out.crc

You can print the CRC to stdout with the command:

        avconv -i INPUT -f crc -

You can select the output format of each frame with avconv by specifying the audio and video codec and format. For example to compute the CRC of the input audio converted to PCM unsigned 8-bit and the input video converted to MPEG-2 video, use the command:

        avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f crc -

See also the framecrc muxer.

framecrc¶

Per-frame CRC (Cyclic Redundancy Check) testing format. This muxer computes and prints the Adler-32 CRC for each decoded audio and video frame. By default audio frames are converted to signed 16-bit raw audio and video frames to raw video before computing the CRC. The output of the muxer consists of a line for each audio and video frame of the form: stream_index, frame_dts, frame_size, 0xCRC, where CRC is a hexadecimal number 0-padded to 8 digits containing the CRC of the decoded frame. For example to compute the CRC of each decoded frame in the input, and store it in the file out.crc:

        avconv -i INPUT -f framecrc out.crc

You can print the CRC of each decoded frame to stdout with the command:

        avconv -i INPUT -f framecrc -

You can select the output format of each frame with avconv by specifying the audio and video codec and format. For example, to compute the CRC of each decoded input audio frame converted to PCM unsigned 8-bit and of each decoded input video frame converted to MPEG-2 video, use the command:

        avconv -i INPUT -c:a pcm_u8 -c:v mpeg2video -f framecrc -

See also the crc muxer.

hls¶

Apple HTTP Live Streaming muxer that segments MPEG-TS according to the HTTP Live Streaming specification. It creates a playlist file and numbered segment files. The output filename specifies the playlist filename; the segment filenames receive the same basename as the playlist, a sequential number and a .ts extension.

        avconv -i in.nut out.m3u8

-hls_time seconds

Set the segment length in seconds.

-hls_list_size size

Set the maximum number of playlist entries.

-hls_wrap wrap

Set the number after which index wraps.

-start_number number

Start the sequence from number.

-hls_base_url baseurl

Append baseurl to every entry in the playlist. Useful to generate playlists with absolute paths.

image2¶

Image file muxer. The image file muxer writes video frames to image files. The output filenames are specified by a pattern, which can be used to produce sequentially numbered series of files. The pattern may contain the string "%d" or "%0 Nd", this string specifies the position of the characters representing a numbering in the filenames. If the form "%0 Nd" is used, the string representing the number in each filename is 0-padded to N digits. The literal character '%' can be specified in the pattern with the string "%%". If the pattern contains "%d" or "%0 Nd", the first filename of the file list specified will contain the number 1, all the following numbers will be sequential. The pattern may contain a suffix which is used to automatically determine the format of the image files to write. For example the pattern "img-%03d.bmp" will specify a sequence of filenames of the form img-001.bmp, img-002.bmp, ..., img-010.bmp, etc. The pattern "img%%-%d.jpg" will specify a sequence of filenames of the form img%-1.jpg, img%-2.jpg, ..., img%-10.jpg, etc. The following example shows how to use avconv for creating a sequence of files img-001.jpeg, img-002.jpeg, ..., taking one image every second from the input video:

        avconv -i in.avi -vsync 1 -r 1 -f image2 'img-%03d.jpeg'

Note that with avconv, if the format is not specified with the "-f" option and the output filename specifies an image file format, the image2 muxer is automatically selected, so the previous command can be written as:

        avconv -i in.avi -vsync 1 -r 1 'img-%03d.jpeg'

Note also that the pattern must not necessarily contain "%d" or "%0 Nd", for example to create a single image file img.jpeg from the input video you can employ the command:

        avconv -i in.avi -f image2 -frames:v 1 img.jpeg

-start_number number

Start the sequence from number.

-update number

If number is nonzero, the filename will always be interpreted as just a filename, not a pattern, and this file will be continuously overwritten with new images.

matroska¶

Matroska container muxer. This muxer implements the matroska and webm container specs. The recognized metadata settings in this muxer are:

title=title name

Name provided to a single track

language=language name

Specifies the language of the track in the Matroska languages form

STEREO_MODE=mode

Stereo 3D video layout of two views in a single video track

For example a 3D WebM clip can be created using the following command line:

        avconv -i sample_left_right_clip.mpg -an -c:v libvpx -metadata STEREO_MODE=left_right -y stereo_clip.webm

This muxer supports the following options:

reserve_index_space

By default, this muxer writes the index for seeking (called cues in Matroska terms) at the end of the file, because it cannot know in advance how much space to leave for the index at the beginning of the file. However for some use cases -- e.g. streaming where seeking is possible but slow -- it is useful to put the index at the beginning of the file.

If this option is set to a non-zero value, the muxer will reserve a given amount of space in the file header and then try to write the cues there when the muxing finishes. If the available space does not suffice, muxing will fail. A safe size for most use cases should be about 50kB per hour of video.

Note that cues are only written if the output is seekable and this option will have no effect if it is not.

mov, mp4, ismv¶

The mov/mp4/ismv muxer supports fragmentation. Normally, a MOV/MP4 file has all the metadata about all packets stored in one location (written at the end of the file, it can be moved to the start for better playback using the qt-faststart tool). A fragmented file consists of a number of fragments, where packets and metadata about these packets are stored together. Writing a fragmented file has the advantage that the file is decodable even if the writing is interrupted (while a normal MOV/MP4 is undecodable if it is not properly finished), and it requires less memory when writing very long files (since writing normal MOV/MP4 files stores info about every single packet in memory until the file is closed). The downside is that it is less compatible with other applications. Fragmentation is enabled by setting one of the AVOptions that define how to cut the file into fragments:

-movflags frag_keyframe

Start a new fragment at each video keyframe.

-frag_duration duration

Create fragments that are duration microseconds long.

-frag_size size

Create fragments that contain up to size bytes of payload data.

-movflags frag_custom

Allow the caller to manually choose when to cut fragments, by calling "av_write_frame(ctx, NULL)" to write a fragment with the packets written so far. (This is only useful with other applications integrating libavformat, not from avconv.)

-min_frag_duration duration

Don't create fragments that are shorter than duration microseconds long.

If more than one condition is specified, fragments are cut when one of the specified conditions is fulfilled. The exception to this is "-min_frag_duration", which has to be fulfilled for any of the other conditions to apply. Additionally, the way the output file is written can be adjusted through a few other options:

-movflags empty_moov

Write an initial moov atom directly at the start of the file, without describing any samples in it. Generally, an mdat/moov pair is written at the start of the file, as a normal MOV/MP4 file, containing only a short portion of the file. With this option set, there is no initial mdat atom, and the moov atom only describes the tracks but has a zero duration.

Files written with this option set do not work in QuickTime. This option is implicitly set when writing ismv (Smooth Streaming) files.

-movflags separate_moof

Write a separate moof (movie fragment) atom for each track. Normally, packets for all tracks are written in a moof atom (which is slightly more efficient), but with this option set, the muxer writes one moof/mdat pair for each track, making it easier to separate tracks.

This option is implicitly set when writing ismv (Smooth Streaming) files.

-movflags faststart

Run a second pass moving the index (moov atom) to the beginning of the file. This operation can take a while, and will not work in various situations such as fragmented output, thus it is not enabled by default.

-movflags disable_chpl

Disable Nero chapter markers (chpl atom). Normally, both Nero chapters and a QuickTime chapter track are written to the file. With this option set, only the QuickTime chapter track will be written. Nero chapters can cause failures when the file is reprocessed with certain tagging programs.

Smooth Streaming content can be pushed in real time to a publishing point on IIS with this muxer. Example:

        avconv -re <<normal input/transcoding options>> -movflags isml+frag_keyframe -f ismv http://server/publishingpoint.isml/Streams(Encoder1)

mp3¶

The MP3 muxer writes a raw MP3 stream with an ID3v2 header at the beginning and optionally an ID3v1 tag at the end. ID3v2.3 and ID3v2.4 are supported, the "id3v2_version" option controls which one is used. Setting "id3v2_version" to 0 will disable the ID3v2 header completely. The legacy ID3v1 tag is not written by default, but may be enabled with the "write_id3v1" option. The muxer may also write a Xing frame at the beginning, which contains the number of frames in the file. It is useful for computing duration of VBR files. The Xing frame is written if the output stream is seekable and if the "write_xing" option is set to 1 (the default). The muxer supports writing ID3v2 attached pictures (APIC frames). The pictures are supplied to the muxer in form of a video stream with a single packet. There can be any number of those streams, each will correspond to a single APIC frame. The stream metadata tags title and comment map to APIC description and picture type respectively. See < http://id3.org/id3v2.4.0-frames> for allowed picture types. Note that the APIC frames must be written at the beginning, so the muxer will buffer the audio frames until it gets all the pictures. It is therefore advised to provide the pictures as soon as possible to avoid excessive buffering. Examples: Write an mp3 with an ID3v2.3 header and an ID3v1 footer:

        avconv -i INPUT -id3v2_version 3 -write_id3v1 1 out.mp3

Attach a picture to an mp3:

        avconv -i input.mp3 -i cover.png -c copy -metadata:s:v title="Album cover"
        -metadata:s:v comment="Cover (Front)" out.mp3

Write a "clean" MP3 without any extra features:

        avconv -i input.wav -write_xing 0 -id3v2_version 0 out.mp3

mpegts¶

MPEG transport stream muxer. This muxer implements ISO 13818-1 and part of ETSI EN 300 468. The muxer options are:

-mpegts_original_network_id number

Set the original_network_id (default 0x0001). This is unique identifier of a network in DVB. Its main use is in the unique identification of a service through the path Original_Network_ID, Transport_Stream_ID.

-mpegts_transport_stream_id number

Set the transport_stream_id (default 0x0001). This identifies a transponder in DVB.

-mpegts_service_id number

Set the service_id (default 0x0001) also known as program in DVB.

-mpegts_pmt_start_pid number

Set the first PID for PMT (default 0x1000, max 0x1f00).

-mpegts_start_pid number

Set the first PID for data packets (default 0x0100, max 0x0f00).

-muxrate number

Set a constant muxrate (default VBR).

-pcr_period numer

Override the default PCR retransmission time (default 20ms), ignored if variable muxrate is selected.

The recognized metadata settings in mpegts muxer are "service_provider" and "service_name". If they are not set the default for "service_provider" is "Libav" and the default for "service_name" is "Service01".

        avconv -i file.mpg -c copy \
             -mpegts_original_network_id 0x1122 \
             -mpegts_transport_stream_id 0x3344 \
             -mpegts_service_id 0x5566 \
             -mpegts_pmt_start_pid 0x1500 \
             -mpegts_start_pid 0x150 \
             -metadata service_provider="Some provider" \
             -metadata service_name="Some Channel" \
             -y out.ts

null¶

Null muxer. This muxer does not generate any output file, it is mainly useful for testing or benchmarking purposes. For example to benchmark decoding with avconv you can use the command:

        avconv -benchmark -i INPUT -f null out.null

Note that the above command does not read or write the out.null file, but specifying the output file is required by the avconv syntax. Alternatively you can write the command as:

        avconv -benchmark -i INPUT -f null -

nut¶

-syncpoints flags

Change the syncpoint usage in nut:

        avconv -i INPUT -f_strict experimental -syncpoints none - | processor

ogg¶

Ogg container muxer.

-page_duration duration

Preferred page duration, in microseconds. The muxer will attempt to create pages that are approximately duration microseconds long. This allows the user to compromise between seek granularity and container overhead. The default is 1 second. A value of 0 will fill all segments, making pages as large as possible. A value of 1 will effectively use 1 packet-per-page in most situations, giving a small seek granularity at the cost of additional container overhead.

segment¶

Basic stream segmenter. The segmenter muxer outputs streams to a number of separate files of nearly fixed duration. Output filename pattern can be set in a fashion similar to image2. Every segment starts with a video keyframe, if a video stream is present. The segment muxer works best with a single constant frame rate video. Optionally it can generate a flat list of the created segments, one segment per line.

segment_format format

Override the inner container format, by default it is guessed by the filename extension.

segment_time t

Set segment duration to t seconds.

segment_list name

Generate also a listfile named name.

segment_list_type type

Select the listing format.

segment_list_size size

Overwrite the listfile once it reaches size entries.

segment_list_entry_prefix prefix

Prepend prefix to each entry. Useful to generate absolute paths.

segment_wrap limit

Wrap around segment index once it reaches limit.

        avconv -i in.mkv -c copy -map 0 -f segment -list out.list out%03d.nut

Protocols are configured elements in Libav which allow to access resources which require the use of a particular protocol. When you configure your Libav build, all the supported protocols are enabled by default. You can list all available ones using the configure option "--list-protocols". You can disable all the protocols using the configure option "--disable-protocols", and selectively enable a protocol using the option "--enable-protocol= PROTOCOL", or you can disable a particular protocol using the option "--disable-protocol= PROTOCOL". The option "-protocols" of the av* tools will display the list of supported protocols. A description of the currently available protocols follows.

concat¶

Physical concatenation protocol. Allow to read and seek from many resource in sequence as if they were a unique resource. A URL accepted by this protocol has the syntax:

        concat:<URL1>|<URL2>|...|<URLN>

where URL1, URL2, ..., URLN are the urls of the resource to be concatenated, each one possibly specifying a distinct protocol. For example to read a sequence of files split1.mpeg, split2.mpeg, split3.mpeg with avplay use the command:

        avplay concat:split1.mpeg\|split2.mpeg\|split3.mpeg

Note that you may need to escape the character "|" which is special for many shells.

file¶

File access protocol. Allow to read from or read to a file. For example to read from a file input.mpeg with avconv use the command:

        avconv -i file:input.mpeg output.mpeg

The av* tools default to the file protocol, that is a resource specified with the name "FILE.mpeg" is interpreted as the URL "file:FILE.mpeg".

gopher¶

Gopher protocol.

hls¶

Read Apple HTTP Live Streaming compliant segmented stream as a uniform one. The M3U8 playlists describing the segments can be remote HTTP resources or local files, accessed using the standard file protocol. The nested protocol is declared by specifying "+ proto" after the hls URI scheme name, where proto is either "file" or "http".

        hls+http://host/path/to/remote/resource.m3u8
        hls+file://path/to/local/resource.m3u8

Using this protocol is discouraged - the hls demuxer should work just as well (if not, please report the issues) and is more complete. To use the hls demuxer instead, simply use the direct URLs to the m3u8 files.

http¶

HTTP (Hyper Text Transfer Protocol). This protocol accepts the following options:

chunked_post

If set to 1 use chunked Transfer-Encoding for posts, default is 1.

content_type

Set a specific content type for the POST messages.

headers

Set custom HTTP headers, can override built in default headers. The value must be a string encoding the headers.

multiple_requests

Use persistent connections if set to 1, default is 0.

post_data

Set custom HTTP post data.

user_agent

Override the User-Agent header. If not specified a string of the form "Lavf/<version>" will be used.

mime_type

Export the MIME type.

icy

If set to 1 request ICY (SHOUTcast) metadata from the server. If the server supports this, the metadata has to be retrieved by the application by reading the icy_metadata_headers and icy_metadata_packet options. The default is 1.

icy_metadata_headers

If the server supports ICY metadata, this contains the ICY-specific HTTP reply headers, separated by newline characters.

icy_metadata_packet

If the server supports ICY metadata, and icy was set to 1, this contains the last non-empty metadata packet sent by the server. It should be polled in regular intervals by applications interested in mid-stream metadata updates.

offset

Set initial byte offset.

end_offset

Try to limit the request to bytes preceding this offset.

Icecast¶

Icecast (stream to Icecast servers) This protocol accepts the following options:

ice_genre

Set the stream genre.

ice_name

Set the stream name.

ice_description

Set the stream description.

ice_url

Set the stream website URL.

ice_public

Set if the stream should be public or not. The default is 0 (not public).

user_agent

Override the User-Agent header. If not specified a string of the form "Lavf/<version>" will be used.

password

Set the Icecast mountpoint password.

content_type

Set the stream content type. This must be set if it is different from audio/mpeg.

legacy_icecast

This enables support for Icecast versions < 2.4.0, that do not support the HTTP PUT method but the SOURCE method.

mmst¶

MMS (Microsoft Media Server) protocol over TCP.

mmsh¶

MMS (Microsoft Media Server) protocol over HTTP. The required syntax is:

        mmsh://<server>[:<port>][/<app>][/<playpath>]

md5¶

MD5 output protocol. Computes the MD5 hash of the data to be written, and on close writes this to the designated output or stdout if none is specified. It can be used to test muxers without writing an actual file. Some examples follow.

        # Write the MD5 hash of the encoded AVI file to the file output.avi.md5.
        avconv -i input.flv -f avi -y md5:output.avi.md5
        
        # Write the MD5 hash of the encoded AVI file to stdout.
        avconv -i input.flv -f avi -y md5:

Note that some formats (typically MOV) require the output protocol to be seekable, so they will fail with the MD5 output protocol.

pipe¶

UNIX pipe access protocol. Allow to read and write from UNIX pipes. The accepted syntax is:

        pipe:[<number>]

number is the number corresponding to the file descriptor of the pipe (e.g. 0 for stdin, 1 for stdout, 2 for stderr). If number is not specified, by default the stdout file descriptor will be used for writing, stdin for reading. For example to read from stdin with avconv:

        cat test.wav | avconv -i pipe:0
        # ...this is the same as...
        cat test.wav | avconv -i pipe:

For writing to stdout with avconv:

        avconv -i test.wav -f avi pipe:1 | cat > test.avi
        # ...this is the same as...
        avconv -i test.wav -f avi pipe: | cat > test.avi

Note that some formats (typically MOV), require the output protocol to be seekable, so they will fail with the pipe output protocol.

rtmp¶

Real-Time Messaging Protocol. The Real-Time Messaging Protocol (RTMP) is used for streaming multimedia content across a TCP/IP network. The required syntax is:

        rtmp://[<username>:<password>@]<server>[:<port>][/<app>][/<instance>][/<playpath>]

The accepted parameters are:

username

An optional username (mostly for publishing).

password

An optional password (mostly for publishing).

server

The address of the RTMP server.

port

The number of the TCP port to use (by default is 1935).

app

It is the name of the application to access. It usually corresponds to the path where the application is installed on the RTMP server (e.g. /ondemand/, /flash/live/, etc.). You can override the value parsed from the URI through the "rtmp_app" option, too.

playpath

It is the path or name of the resource to play with reference to the application specified in app, may be prefixed by "mp4:". You can override the value parsed from the URI through the "rtmp_playpath" option, too.

listen

Act as a server, listening for an incoming connection.

timeout

Maximum time to wait for the incoming connection. Implies listen.

Additionally, the following parameters can be set via command line options (or in code via "AVOption"s):

rtmp_app

Name of application to connect on the RTMP server. This option overrides the parameter specified in the URI.

rtmp_buffer

Set the client buffer time in milliseconds. The default is 3000.

rtmp_conn

Extra arbitrary AMF connection parameters, parsed from a string, e.g. like "B:1 S:authMe O:1 NN:code:1.23 NS:flag:ok O:0". Each value is prefixed by a single character denoting the type, B for Boolean, N for number, S for string, O for object, or Z for null, followed by a colon. For Booleans the data must be either 0 or 1 for FALSE or TRUE, respectively. Likewise for Objects the data must be 0 or 1 to end or begin an object, respectively. Data items in subobjects may be named, by prefixing the type with 'N' and specifying the name before the value (i.e. "NB:myFlag:1"). This option may be used multiple times to construct arbitrary AMF sequences.

rtmp_flashver

Version of the Flash plugin used to run the SWF player. The default is LNX 9,0,124,2. (When publishing, the default is FMLE/3.0 (compatible; <libavformat version>).)

rtmp_flush_interval

Number of packets flushed in the same request (RTMPT only). The default is 10.

rtmp_live

Specify that the media is a live stream. No resuming or seeking in live streams is possible. The default value is "any", which means the subscriber first tries to play the live stream specified in the playpath. If a live stream of that name is not found, it plays the recorded stream. The other possible values are "live" and "recorded".

rtmp_pageurl

URL of the web page in which the media was embedded. By default no value will be sent.

rtmp_playpath

Stream identifier to play or to publish. This option overrides the parameter specified in the URI.

rtmp_subscribe

Name of live stream to subscribe to. By default no value will be sent. It is only sent if the option is specified or if rtmp_live is set to live.

rtmp_swfhash

SHA256 hash of the decompressed SWF file (32 bytes).

rtmp_swfsize

Size of the decompressed SWF file, required for SWFVerification.

rtmp_swfurl

URL of the SWF player for the media. By default no value will be sent.

rtmp_swfverify

URL to player swf file, compute hash/size automatically.

rtmp_tcurl

URL of the target stream. Defaults to proto://host[:port]/app.

For example to read with avplay a multimedia resource named "sample" from the application "vod" from an RTMP server "myserver":

        avplay rtmp://myserver/vod/sample

To publish to a password protected server, passing the playpath and app names separately:

        avconv -re -i <input> -f flv -rtmp_playpath some/long/path -rtmp_app long/app/name rtmp://username:password@myserver/

rtmpe¶

Encrypted Real-Time Messaging Protocol. The Encrypted Real-Time Messaging Protocol (RTMPE) is used for streaming multimedia content within standard cryptographic primitives, consisting of Diffie-Hellman key exchange and HMACSHA256, generating a pair of RC4 keys.

rtmps¶

Real-Time Messaging Protocol over a secure SSL connection. The Real-Time Messaging Protocol (RTMPS) is used for streaming multimedia content across an encrypted connection.

rtmpt¶

Real-Time Messaging Protocol tunneled through HTTP. The Real-Time Messaging Protocol tunneled through HTTP (RTMPT) is used for streaming multimedia content within HTTP requests to traverse firewalls.

rtmpte¶

Encrypted Real-Time Messaging Protocol tunneled through HTTP. The Encrypted Real-Time Messaging Protocol tunneled through HTTP (RTMPTE) is used for streaming multimedia content within HTTP requests to traverse firewalls.

rtmpts¶

Real-Time Messaging Protocol tunneled through HTTPS. The Real-Time Messaging Protocol tunneled through HTTPS (RTMPTS) is used for streaming multimedia content within HTTPS requests to traverse firewalls.

librtmp rtmp, rtmpe, rtmps, rtmpt, rtmpte¶

Real-Time Messaging Protocol and its variants supported through librtmp. Requires the presence of the librtmp headers and library during configuration. You need to explicitly configure the build with "--enable-librtmp". If enabled this will replace the native RTMP protocol. This protocol provides most client functions and a few server functions needed to support RTMP, RTMP tunneled in HTTP (RTMPT), encrypted RTMP (RTMPE), RTMP over SSL/TLS (RTMPS) and tunneled variants of these encrypted types (RTMPTE, RTMPTS). The required syntax is:

        <rtmp_proto>://<server>[:<port>][/<app>][/<playpath>] <options>

where rtmp_proto is one of the strings "rtmp", "rtmpt", "rtmpe", "rtmps", "rtmpte", "rtmpts" corresponding to each RTMP variant, and server, port, app and playpath have the same meaning as specified for the RTMP native protocol. options contains a list of space-separated options of the form key=val. See the librtmp manual page (man 3 librtmp) for more information. For example, to stream a file in real-time to an RTMP server using avconv:

        avconv -re -i myfile -f flv rtmp://myserver/live/mystream

To play the same stream using avplay:

        avplay "rtmp://myserver/live/mystream live=1"

rtp¶

Real-Time Protocol.

rtsp¶

RTSP is not technically a protocol handler in libavformat, it is a demuxer and muxer. The demuxer supports both normal RTSP (with data transferred over RTP; this is used by e.g. Apple and Microsoft) and Real-RTSP (with data transferred over RDT). The muxer can be used to send a stream using RTSP ANNOUNCE to a server supporting it (currently Darwin Streaming Server and Mischa Spiegelmock's
RTSP server ("http://github.com/revmischa/rtsp-server")). The required syntax for a RTSP url is:

        rtsp://<hostname>[:<port>]/<path>

The following options (set on the avconv/avplay command line, or set in code via "AVOption"s or in "avformat_open_input"), are supported: Flags for "rtsp_transport":

udp

Use UDP as lower transport protocol.

tcp

Use TCP (interleaving within the RTSP control channel) as lower transport protocol.

udp_multicast

Use UDP multicast as lower transport protocol.

http

Use HTTP tunneling as lower transport protocol, which is useful for passing proxies.

Multiple lower transport protocols may be specified, in that case they are tried one at a time (if the setup of one fails, the next one is tried). For the muxer, only the "tcp" and "udp" options are supported. Flags for "rtsp_flags":

filter_src

Accept packets only from negotiated peer address and port.

listen

Act as a server, listening for an incoming connection.

When receiving data over UDP, the demuxer tries to reorder received packets (since they may arrive out of order, or packets may get lost totally). This can be disabled by setting the maximum demuxing delay to zero (via the "max_delay" field of AVFormatContext). When watching multi-bitrate Real-RTSP streams with avplay, the streams to display can be chosen with "-vst" n and "-ast" n for video and audio respectively, and can be switched on the fly by pressing "v" and "a". Example command lines: To watch a stream over UDP, with a max reordering delay of 0.5 seconds:

        avplay -max_delay 500000 -rtsp_transport udp rtsp://server/video.mp4

To watch a stream tunneled over HTTP:

        avplay -rtsp_transport http rtsp://server/video.mp4

To send a stream in realtime to a RTSP server, for others to watch:

        avconv -re -i <input> -f rtsp -muxdelay 0.1 rtsp://server/live.sdp

To receive a stream in realtime:

        avconv -rtsp_flags listen -i rtsp://ownaddress/live.sdp <output>

sap¶

Session Announcement Protocol (RFC 2974). This is not technically a protocol handler in libavformat, it is a muxer and demuxer. It is used for signalling of RTP streams, by announcing the SDP for the streams regularly on a separate port. Muxer The syntax for a SAP url given to the muxer is:

        sap://<destination>[:<port>][?<options>]

The RTP packets are sent to destination on port port, or to port 5004 if no port is specified. options is a "&"-separated list. The following options are supported:

announce_addr=address

Specify the destination IP address for sending the announcements to. If omitted, the announcements are sent to the commonly used SAP announcement multicast address 224.2.127.254 (sap.mcast.net), or ff0e::2:7ffe if destination is an IPv6 address.

announce_port=port

Specify the port to send the announcements on, defaults to 9875 if not specified.

ttl=ttl

Specify the time to live value for the announcements and RTP packets, defaults to 255.

same_port=0|1

If set to 1, send all RTP streams on the same port pair. If zero (the default), all streams are sent on unique ports, with each stream on a port 2 numbers higher than the previous. VLC/Live555 requires this to be set to 1, to be able to receive the stream. The RTP stack in libavformat for receiving requires all streams to be sent on unique ports.

Example command lines follow. To broadcast a stream on the local subnet, for watching in VLC:

        avconv -re -i <input> -f sap sap://224.0.0.255?same_port=1

Similarly, for watching in avplay:

        avconv -re -i <input> -f sap sap://224.0.0.255

And for watching in avplay, over IPv6:

        avconv -re -i <input> -f sap sap://[ff0e::1:2:3:4]

Demuxer The syntax for a SAP url given to the demuxer is:

        sap://[<address>][:<port>]

address is the multicast address to listen for announcements on, if omitted, the default 224.2.127.254 (sap.mcast.net) is used. port is the port that is listened on, 9875 if omitted. The demuxers listens for announcements on the given address and port. Once an announcement is received, it tries to receive that particular stream. Example command lines follow. To play back the first stream announced on the normal SAP multicast address:

        avplay sap://

To play back the first stream announced on one the default IPv6 SAP multicast address:

        avplay sap://[ff0e::2:7ffe]

tcp¶

Trasmission Control Protocol. The required syntax for a TCP url is:

        tcp://<hostname>:<port>[?<options>]

listen

Listen for an incoming connection

        avconv -i <input> -f <format> tcp://<hostname>:<port>?listen
        avplay tcp://<hostname>:<port>
    

tls¶

Transport Layer Security (TLS) / Secure Sockets Layer (SSL) The required syntax for a TLS url is:

        tls://<hostname>:<port>

The following parameters can be set via command line options (or in code via "AVOption"s):

ca_file

A file containing certificate authority (CA) root certificates to treat as trusted. If the linked TLS library contains a default this might not need to be specified for verification to work, but not all libraries and setups have defaults built in.

tls_verify=1|0

If enabled, try to verify the peer that we are communicating with. Note, if using OpenSSL, this currently only makes sure that the peer certificate is signed by one of the root certificates in the CA database, but it does not validate that the certificate actually matches the host name we are trying to connect to. (With GnuTLS, the host name is validated as well.)

This is disabled by default since it requires a CA database to be provided by the caller in many cases.

cert_file

A file containing a certificate to use in the handshake with the peer. (When operating as server, in listen mode, this is more often required by the peer, while client certificates only are mandated in certain setups.)

key_file

A file containing the private key for the certificate.

listen=1|0

If enabled, listen for connections on the provided port, and assume the server role in the handshake instead of the client role.

udp¶

User Datagram Protocol. The required syntax for a UDP url is:

        udp://<hostname>:<port>[?<options>]

options contains a list of &-separated options of the form key= val. Follow the list of supported options.

buffer_size=size

set the UDP buffer size in bytes

localport=port

override the local UDP port to bind with

localaddr=addr

Choose the local IP address. This is useful e.g. if sending multicast and the host has multiple interfaces, where the user can choose which interface to send on by specifying the IP address of that interface.

pkt_size=size

set the size in bytes of UDP packets

reuse=1|0

explicitly allow or disallow reusing UDP sockets

ttl=ttl

set the time to live value (for multicast only)

connect=1|0

Initialize the UDP socket with "connect()". In this case, the destination address can't be changed with ff_udp_set_remote_url later. If the destination address isn't known at the start, this option can be specified in ff_udp_set_remote_url, too. This allows finding out the source address for the packets with getsockname, and makes writes return with AVERROR(ECONNREFUSED) if "destination unreachable" is received. For receiving, this gives the benefit of only receiving packets from the specified peer address/port.

sources=address[,address]

Only receive packets sent to the multicast group from one of the specified sender IP addresses.

block=address[,address]

Ignore packets sent to the multicast group from the specified sender IP addresses.

Some usage examples of the udp protocol with avconv follow. To stream over UDP to a remote endpoint:

        avconv -i <input> -f <format> udp://<hostname>:<port>

To stream in mpegts format over UDP using 188 sized UDP packets, using a large input buffer:

        avconv -i <input> -f mpegts udp://<hostname>:<port>?pkt_size=188&buffer_size=65535

To receive over UDP from a remote endpoint:

        avconv -i udp://[<multicast-address>]:<port>

unix¶

Unix local socket The required syntax for a Unix socket URL is:

        unix://<filepath>

The following parameters can be set via command line options (or in code via "AVOption"s):

timeout

Timeout in ms.

listen

Create the Unix socket in listening mode.

Input devices are configured elements in Libav which allow to access the data coming from a multimedia device attached to your system. When you configure your Libav build, all the supported input devices are enabled by default. You can list all available ones using the configure option "--list-indevs". You can disable all the input devices using the configure option "--disable-indevs", and selectively enable an input device using the option "--enable-indev= INDEV", or you can disable a particular input device using the option "--disable-indev= INDEV". The option "-formats" of the av* tools will display the list of supported input devices (amongst the demuxers). A description of the currently available input devices follows.

alsa¶

ALSA (Advanced Linux Sound Architecture) input device. To enable this input device during configuration you need libasound installed on your system. This device allows capturing from an ALSA device. The name of the device to capture has to be an ALSA card identifier. An ALSA identifier has the syntax:

        hw:<CARD>[,<DEV>[,<SUBDEV>]]

where the DEV and SUBDEV components are optional. The three arguments (in order: CARD,DEV,SUBDEV) specify card number or identifier, device number and subdevice number (-1 means any). To see the list of cards currently recognized by your system check the files /proc/asound/cards and /proc/asound/devices. For example to capture with avconv from an ALSA device with card id 0, you may run the command:

        avconv -f alsa -i hw:0 alsaout.wav

For more information see: < http://www.alsa-project.org/alsa-doc/alsa-lib/pcm.html>

bktr¶

BSD video input device.

dv1394¶

Linux DV 1394 input device.

fbdev¶

Linux framebuffer input device. The Linux framebuffer is a graphic hardware-independent abstraction layer to show graphics on a computer monitor, typically on the console. It is accessed through a file device node, usually /dev/fb0. For more detailed information read the file Documentation/fb/framebuffer.txt included in the Linux source tree. To record from the framebuffer device /dev/fb0 with avconv:

        avconv -f fbdev -r 10 -i /dev/fb0 out.avi

You can take a single screenshot image with the command:

        avconv -f fbdev -frames:v 1 -r 1 -i /dev/fb0 screenshot.jpeg

See also < http://linux-fbdev.sourceforge.net/>, and fbset(1).

jack¶

JACK input device. To enable this input device during configuration you need libjack installed on your system. A JACK input device creates one or more JACK writable clients, one for each audio channel, with name client_name:input_N, where client_name is the name provided by the application, and N is a number which identifies the channel. Each writable client will send the acquired data to the Libav input device. Once you have created one or more JACK readable clients, you need to connect them to one or more JACK writable clients. To connect or disconnect JACK clients you can use the jack_connect and jack_disconnect programs, or do it through a graphical interface, for example with qjackctl. To list the JACK clients and their properties you can invoke the command jack_lsp. Follows an example which shows how to capture a JACK readable client with avconv.

        # Create a JACK writable client with name "libav".
        $ avconv -f jack -i libav -y out.wav
        
        # Start the sample jack_metro readable client.
        $ jack_metro -b 120 -d 0.2 -f 4000
        
        # List the current JACK clients.
        $ jack_lsp -c
        system:capture_1
        system:capture_2
        system:playback_1
        system:playback_2
        libav:input_1
        metro:120_bpm
        
        # Connect metro to the avconv writable client.
        $ jack_connect metro:120_bpm libav:input_1

For more information read: < http://jackaudio.org/>

libdc1394¶

IIDC1394 input device, based on libdc1394 and libraw1394.

oss¶

Open Sound System input device. The filename to provide to the input device is the device node representing the OSS input device, and is usually set to /dev/dsp. For example to grab from /dev/dsp using avconv use the command:

        avconv -f oss -i /dev/dsp /tmp/oss.wav

For more information about OSS see: < http://manuals.opensound.com/usersguide/dsp.html>

pulse¶

pulseaudio input device. To enable this input device during configuration you need libpulse-simple installed in your system. The filename to provide to the input device is a source device or the string "default" To list the pulse source devices and their properties you can invoke the command pactl list sources.

        avconv -f pulse -i default /tmp/pulse.wav

server AVOption The syntax is:

        -server <server name>

Connects to a specific server. name AVOption The syntax is:

        -name <application name>

Specify the application name pulse will use when showing active clients, by default it is "libav" stream_name AVOption The syntax is:

        -stream_name <stream name>

Specify the stream name pulse will use when showing active streams, by default it is "record" sample_rate AVOption The syntax is:

        -sample_rate <samplerate>

Specify the samplerate in Hz, by default 48kHz is used. channels AVOption The syntax is:

        -channels <N>

Specify the channels in use, by default 2 (stereo) is set. frame_size AVOption The syntax is:

        -frame_size <bytes>

Specify the number of byte per frame, by default it is set to 1024. fragment_size AVOption The syntax is:

        -fragment_size <bytes>

Specify the minimal buffering fragment in pulseaudio, it will affect the audio latency. By default it is unset.

sndio¶

sndio input device. To enable this input device during configuration you need libsndio installed on your system. The filename to provide to the input device is the device node representing the sndio input device, and is usually set to /dev/audio0. For example to grab from /dev/audio0 using avconv use the command:

        avconv -f sndio -i /dev/audio0 /tmp/oss.wav

video4linux2¶

Video4Linux2 input video device. The name of the device to grab is a file device node, usually Linux systems tend to automatically create such nodes when the device (e.g. an USB webcam) is plugged into the system, and has a name of the kind /dev/videoN, where N is a number associated to the device. Video4Linux2 devices usually support a limited set of widthxheight sizes and framerates. You can check which are supported using -list_formats all for Video4Linux2 devices. Some usage examples of the video4linux2 devices with avconv and avplay:

        # Grab and show the input of a video4linux2 device.
        avplay -f video4linux2 -framerate 30 -video_size hd720 /dev/video0
        
        # Grab and record the input of a video4linux2 device, leave the
        framerate and size as previously set.
        avconv -f video4linux2 -input_format mjpeg -i /dev/video0 out.mpeg

vfwcap¶

VfW (Video for Windows) capture input device. The filename passed as input is the capture driver number, ranging from 0 to 9. You may use "list" as filename to print a list of drivers. Any other filename will be interpreted as device number 0.

x11grab¶

X11 video input device. This device allows to capture a region of an X11 display. The filename passed as input has the syntax:

        [<hostname>]:<display_number>.<screen_number>[+<x_offset>,<y_offset>]

hostname:display_number.screen_number specifies the X11 display name of the screen to grab from. hostname can be omitted, and defaults to "localhost". The environment variable DISPLAY contains the default display name. x_offset and y_offset specify the offsets of the grabbed area with respect to the top-left border of the X11 screen. They default to 0. Check the X11 documentation (e.g. man X) for more detailed information. Use the dpyinfo program for getting basic information about the properties of your X11 display (e.g. grep for "name" or "dimensions"). For example to grab from :0.0 using avconv:

        avconv -f x11grab -r 25 -s cif -i :0.0 out.mpg
        
        # Grab at position 10,20.
        avconv -f x11grab -r 25 -s cif -i :0.0+10,20 out.mpg

follow_mouse AVOption The syntax is:

        -follow_mouse centered|<PIXELS>

When it is specified with "centered", the grabbing region follows the mouse pointer and keeps the pointer at the center of region; otherwise, the region follows only when the mouse pointer reaches within PIXELS (greater than zero) to the edge of region. For example:

        avconv -f x11grab -follow_mouse centered -r 25 -s cif -i :0.0 out.mpg
        
        # Follows only when the mouse pointer reaches within 100 pixels to edge
        avconv -f x11grab -follow_mouse 100 -r 25 -s cif -i :0.0 out.mpg

show_region AVOption The syntax is:

        -show_region 1

If show_region AVOption is specified with 1, then the grabbing region will be indicated on screen. With this option, it's easy to know what is being grabbed if only a portion of the screen is grabbed. For example:

        avconv -f x11grab -show_region 1 -r 25 -s cif -i :0.0+10,20 out.mpg
        
        # With follow_mouse
        avconv -f x11grab -follow_mouse centered -show_region 1  -r 25 -s cif -i :0.0 out.mpg

avconv(1), avplay(1) and the Libav HTML documentation The Libav developers