mirror of https://git.ffmpeg.org/ffmpeg.git
282 lines
8.3 KiB
Plaintext
282 lines
8.3 KiB
Plaintext
@chapter Bitstream Filters
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@c man begin BITSTREAM FILTERS
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When you configure your Libav 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 av* tools will display the list of
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all the supported bitstream filters included in your build.
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Below is a description of the currently available bitstream filters.
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@section aac_adtstoasc
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@section chomp
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@section dump_extradata
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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 Libav 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_metadata
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Modify metadata embedded in an H.264 stream.
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@table @option
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@item aud
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Insert or remove AUD NAL units in all access units of the stream.
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@table @samp
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@item insert
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@item remove
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@end table
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@item sample_aspect_ratio
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Set the sample aspect ratio of the stream in the VUI parameters.
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@item video_format
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@item video_full_range_flag
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Set the video format in the stream (see H.264 section E.2.1 and
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table E-2).
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@item colour_primaries
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@item transfer_characteristics
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@item matrix_coefficients
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Set the colour description in the stream (see H.264 section E.2.1
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and tables E-3, E-4 and E-5).
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@item chroma_sample_loc_type
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Set the chroma sample location in the stream (see H.264 section
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E.2.1 and figure E-1).
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@item tick_rate
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Set the tick rate (num_units_in_tick / time_scale) in the VUI
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parameters. This is the smallest time unit representable in the
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stream, and in many cases represents the field rate of the stream
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(double the frame rate).
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@item fixed_frame_rate_flag
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Set whether the stream has fixed framerate - typically this indicates
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that the framerate is exactly half the tick rate, but the exact
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meaning is dependent on interlacing and the picture structure (see
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H.264 section E.2.1 and table E-6).
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@item crop_left
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@item crop_right
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@item crop_top
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@item crop_bottom
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Set the frame cropping offsets in the SPS. These values will replace
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the current ones if the stream is already cropped.
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These fields are set in pixels. Note that some sizes may not be
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representable if the chroma is subsampled or the stream is interlaced
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(see H.264 section 7.4.2.1.1).
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@item sei_user_data
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Insert a string as SEI unregistered user data. The argument must
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be of the form @emph{UUID+string}, where the UUID is as hex digits
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possibly separated by hyphens, and the string can be anything.
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For example, @samp{086f3693-b7b3-4f2c-9653-21492feee5b8+hello} will
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insert the string ``hello'' associated with the given UUID.
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@end table
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@section h264_mp4toannexb
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@section h264_redundant_pps
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This applies a specific fixup to some Bluray streams which contain
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redundant PPSs modifying irrelevant parameters of the stream which
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confuse other transformations which require correct extradata.
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A new single global PPS is created, and all of the redundant PPSs
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within the stream are removed.
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@section hevc_metadata
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Modify metadata embedded in an HEVC stream.
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@table @option
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@item aud
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Insert or remove AUD NAL units in all access units of the stream.
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@table @samp
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@item insert
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@item remove
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@end table
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@item sample_aspect_ratio
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Set the sample aspect ratio in the stream in the VUI parameters.
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@item video_format
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@item video_full_range_flag
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Set the video format in the stream (see H.265 section E.3.1 and
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table E.2).
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@item colour_primaries
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@item transfer_characteristics
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@item matrix_coefficients
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Set the colour description in the stream (see H.265 section E.3.1
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and tables E.3, E.4 and E.5).
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@item chroma_sample_loc_type
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Set the chroma sample location in the stream (see H.265 section
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E.3.1 and figure E.1).
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@item tick_rate
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Set the tick rate in the VPS and VUI parameters (num_units_in_tick /
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time_scale). Combined with @option{num_ticks_poc_diff_one}, this can
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set a constant framerate in the stream. Note that it is likely to be
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overridden by container parameters when the stream is in a container.
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@item num_ticks_poc_diff_one
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Set poc_proportional_to_timing_flag in VPS and VUI and use this value
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to set num_ticks_poc_diff_one_minus1 (see H.265 sections 7.4.3.1 and
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E.3.1). Ignored if @option{tick_rate} is not also set.
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@item crop_left
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@item crop_right
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@item crop_top
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@item crop_bottom
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Set the conformance window cropping offsets in the SPS. These values
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will replace the current ones if the stream is already cropped.
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These fields are set in pixels. Note that some sizes may not be
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representable if the chroma is subsampled (H.265 section 7.4.3.2.1).
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@end table
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@section imx_dump_header
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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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avconv -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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avconv -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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avconv -i frame_%d.jpg -c:v copy rotated.avi
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@end example
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@section mjpega_dump_header
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@section movsub
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@section mpeg2_metadata
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Modify metadata embedded in an MPEG-2 stream.
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@table @option
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@item display_aspect_ratio
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Set the display aspect ratio in the stream.
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The following fixed values are supported:
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@table @option
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@item 4/3
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@item 16/9
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@item 221/100
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@end table
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Any other value will result in square pixels being signalled instead
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(see H.262 section 6.3.3 and table 6-3).
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@item frame_rate
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Set the frame rate in the stream. This is constructed from a table
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of known values combined with a small multiplier and divisor - if
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the supplied value is not exactly representable, the nearest
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representable value will be used instead (see H.262 section 6.3.3
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and table 6-4).
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@item video_format
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Set the video format in the stream (see H.262 section 6.3.6 and
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table 6-6).
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@item colour_primaries
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@item transfer_characteristics
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@item matrix_coefficients
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Set the colour description in the stream (see H.262 section 6.3.6
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and tables 6-7, 6-8 and 6-9).
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@end table
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@section mp3_header_compress
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@section mp3_header_decompress
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@section noise
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@section null
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This bitstream filter passes the packets through unchanged.
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@section remove_extradata
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@section trace_headers
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Log trace output containing all syntax elements in the coded stream
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headers (everything above the level of individual coded blocks).
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This can be useful for debugging low-level stream issues.
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Supports H.264, H.265 and MPEG-2.
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@section vp9_superframe
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Combine VP9 frames into superframes.
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@section vp9_superframe_split
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Split VP9 superframes into single frames.
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@section vp9_raw_reorder
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Given a VP9 stream with correct timestamps but possibly out of order,
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insert additional show-existing-frame packets to correct the ordering.
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@c man end BITSTREAM FILTERS
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