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* commit '03a80925effc2698d21dc0b00290eecf42dd9e68': lavc: add a bitstream filter for splitting VP9 superframes Merged-by: James Almer <jamrial@gmail.com>
281 lines
8.5 KiB
Plaintext
281 lines
8.5 KiB
Plaintext
@chapter Bitstream Filters
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@c man begin BITSTREAM FILTERS
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When you configure your FFmpeg build, all the supported bitstream
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filters are enabled by default. You can list all available ones using
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the configure option @code{--list-bsfs}.
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You can disable all the bitstream filters using the configure option
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@code{--disable-bsfs}, and selectively enable any bitstream filter using
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the option @code{--enable-bsf=BSF}, or you can disable a particular
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bitstream filter using the option @code{--disable-bsf=BSF}.
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The option @code{-bsfs} of the ff* tools will display the list of
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all the supported bitstream filters included in your build.
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The ff* tools have a -bsf option applied per stream, taking a
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comma-separated list of filters, whose parameters follow the filter
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name after a '='.
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@example
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ffmpeg -i INPUT -c:v copy -bsf:v filter1[=opt1=str1:opt2=str2][,filter2] OUTPUT
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@end example
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Below is a description of the currently available bitstream filters,
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with their parameters, if any.
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@section aac_adtstoasc
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Convert MPEG-2/4 AAC ADTS to an MPEG-4 Audio Specific Configuration
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bitstream.
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This filter creates an MPEG-4 AudioSpecificConfig from an MPEG-2/4
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ADTS header and removes the ADTS header.
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This filter is required for example when copying an AAC stream from a
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raw ADTS AAC or an MPEG-TS container to MP4A-LATM, to an FLV file, or
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to MOV/MP4 files and related formats such as 3GP or M4A. Please note
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that it is auto-inserted for MP4A-LATM and MOV/MP4 and related formats.
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@section chomp
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Remove zero padding at the end of a packet.
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@section dca_core
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Extract the core from a DCA/DTS stream, dropping extensions such as
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DTS-HD.
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@section dump_extra
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Add extradata to the beginning of the filtered packets.
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The additional argument specifies which packets should be filtered.
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It accepts the values:
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@table @samp
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@item a
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add extradata to all key packets, but only if @var{local_header} is
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set in the @option{flags2} codec context field
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@item k
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add extradata to all key packets
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@item e
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add extradata to all packets
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@end table
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If not specified it is assumed @samp{k}.
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For example the following @command{ffmpeg} command forces a global
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header (thus disabling individual packet headers) in the H.264 packets
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generated by the @code{libx264} encoder, but corrects them by adding
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the header stored in extradata to the key packets:
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@example
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ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts
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@end example
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@section extract_extradata
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Extract the in-band extradata.
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Certain codecs allow the long-term headers (e.g. MPEG-2 sequence headers,
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or H.264/HEVC (VPS/)SPS/PPS) to be transmitted either "in-band" (i.e. as a part
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of the bitstream containing the coded frames) or "out of band" (e.g. on the
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container level). This latter form is called "extradata" in FFmpeg terminology.
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This bitstream filter detects the in-band headers and makes them available as
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extradata.
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@table @option
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@item remove
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When this option is enabled, the long-term headers are removed from the
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bitstream after extraction.
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@end table
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@section h264_mp4toannexb
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Convert an H.264 bitstream from length prefixed mode to start code
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prefixed mode (as defined in the Annex B of the ITU-T H.264
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specification).
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This is required by some streaming formats, typically the MPEG-2
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transport stream format (muxer @code{mpegts}).
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For example to remux an MP4 file containing an H.264 stream to mpegts
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format with @command{ffmpeg}, you can use the command:
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@example
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ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts
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@end example
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Please note that this filter is auto-inserted for MPEG-TS (muxer
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@code{mpegts}) and raw H.264 (muxer @code{h264}) output formats.
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@section hevc_mp4toannexb
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Convert an HEVC/H.265 bitstream from length prefixed mode to start code
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prefixed mode (as defined in the Annex B of the ITU-T H.265
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specification).
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This is required by some streaming formats, typically the MPEG-2
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transport stream format (muxer @code{mpegts}).
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For example to remux an MP4 file containing an HEVC stream to mpegts
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format with @command{ffmpeg}, you can use the command:
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@example
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ffmpeg -i INPUT.mp4 -codec copy -bsf:v hevc_mp4toannexb OUTPUT.ts
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@end example
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Please note that this filter is auto-inserted for MPEG-TS (muxer
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@code{mpegts}) and raw HEVC/H.265 (muxer @code{h265} or
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@code{hevc}) output formats.
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@section imxdump
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Modifies the bitstream to fit in MOV and to be usable by the Final Cut
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Pro decoder. This filter only applies to the mpeg2video codec, and is
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likely not needed for Final Cut Pro 7 and newer with the appropriate
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@option{-tag:v}.
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For example, to remux 30 MB/sec NTSC IMX to MOV:
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@example
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ffmpeg -i input.mxf -c copy -bsf:v imxdump -tag:v mx3n output.mov
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@end example
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@section mjpeg2jpeg
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Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
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MJPEG is a video codec wherein each video frame is essentially a
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JPEG image. The individual frames can be extracted without loss,
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e.g. by
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@example
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ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
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@end example
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Unfortunately, these chunks are incomplete JPEG images, because
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they lack the DHT segment required for decoding. Quoting from
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@url{http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml}:
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Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
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commented that "MJPEG, or at least the MJPEG in AVIs having the
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MJPG fourcc, is restricted JPEG with a fixed -- and *omitted* --
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Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2,
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and it must use basic Huffman encoding, not arithmetic or
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progressive. . . . You can indeed extract the MJPEG frames and
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decode them with a regular JPEG decoder, but you have to prepend
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the DHT segment to them, or else the decoder won't have any idea
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how to decompress the data. The exact table necessary is given in
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the OpenDML spec."
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This bitstream filter patches the header of frames extracted from an MJPEG
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stream (carrying the AVI1 header ID and lacking a DHT segment) to
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produce fully qualified JPEG images.
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@example
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ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
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exiftran -i -9 frame*.jpg
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ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
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@end example
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@section mjpegadump
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Add an MJPEG A header to the bitstream, to enable decoding by
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Quicktime.
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@anchor{mov2textsub}
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@section mov2textsub
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Extract a representable text file from MOV subtitles, stripping the
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metadata header from each subtitle packet.
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See also the @ref{text2movsub} filter.
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@section mp3decomp
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Decompress non-standard compressed MP3 audio headers.
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@section mpeg4_unpack_bframes
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Unpack DivX-style packed B-frames.
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DivX-style packed B-frames are not valid MPEG-4 and were only a
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workaround for the broken Video for Windows subsystem.
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They use more space, can cause minor AV sync issues, require more
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CPU power to decode (unless the player has some decoded picture queue
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to compensate the 2,0,2,0 frame per packet style) and cause
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trouble if copied into a standard container like mp4 or mpeg-ps/ts,
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because MPEG-4 decoders may not be able to decode them, since they are
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not valid MPEG-4.
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For example to fix an AVI file containing an MPEG-4 stream with
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DivX-style packed B-frames using @command{ffmpeg}, you can use the command:
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@example
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ffmpeg -i INPUT.avi -codec copy -bsf:v mpeg4_unpack_bframes OUTPUT.avi
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@end example
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@section noise
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Damages the contents of packets without damaging the container. Can be
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used for fuzzing or testing error resilience/concealment.
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Parameters:
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A numeral string, whose value is related to how often output bytes will
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be modified. Therefore, values below or equal to 0 are forbidden, and
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the lower the more frequent bytes will be modified, with 1 meaning
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every byte is modified.
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@example
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ffmpeg -i INPUT -c copy -bsf noise[=1] output.mkv
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@end example
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applies the modification to every byte.
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@section null
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This bitstream filter passes the packets through unchanged.
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@section remove_extra
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Remove extradata from packets.
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It accepts the following parameter:
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@table @option
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@item freq
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Set which frame types to remove extradata from.
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@table @samp
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@item k
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Remove extradata from non-keyframes only.
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@item keyframe
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Remove extradata from keyframes only.
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@item e, all
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Remove extradata from all frames.
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@end table
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@end table
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@anchor{text2movsub}
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@section text2movsub
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Convert text subtitles to MOV subtitles (as used by the @code{mov_text}
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codec) with metadata headers.
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See also the @ref{mov2textsub} filter.
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@section vp9_superframe
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Merge VP9 invisible (alt-ref) frames back into VP9 superframes. This
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fixes merging of split/segmented VP9 streams where the alt-ref frame
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was split from its visible counterpart.
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@section vp9_superframe_split
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Split VP9 superframes into single frames.
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@c man end BITSTREAM FILTERS
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