FFMPEG-BITSTREAM-FILTERS(1)			   FFMPEG-BITSTREAM-FILTERS(1)

NAME
       ffmpeg-bitstream-filters - FFmpeg bitstream filters

DESCRIPTION
       This document describes the bitstream filters provided by the
       libavcodec library.

       A bitstream filter operates on the encoded stream data, and performs
       bitstream level modifications without performing decoding.

BITSTREAM FILTERS
       When you configure your FFmpeg build, all the supported bitstream
       filters are enabled by default. You can list all available ones using
       the configure option "--list-bsfs".

       You can disable all the bitstream filters using the configure option
       "--disable-bsfs", and selectively enable any bitstream filter using the
       option "--enable-bsf=BSF", or you can disable a particular bitstream
       filter using the option "--disable-bsf=BSF".

       The option "-bsfs" of the ff* tools will display the list of all the
       supported bitstream filters included in your build.

       The ff* tools have a -bsf option applied per stream, taking a comma-
       separated list of filters, whose parameters follow the filter name
       after a '='.

	       ffmpeg -i INPUT -c:v copy -bsf:v filter1[=opt1=str1/opt2=str2][,filter2] OUTPUT

       Below is a description of the currently available bitstream filters,
       with their parameters, if any.

   aac_adtstoasc
       Convert MPEG-2/4 AAC ADTS to MPEG-4 Audio Specific Configuration
       bitstream filter.

       This filter creates an MPEG-4 AudioSpecificConfig from an MPEG-2/4 ADTS
       header and removes the ADTS header.

       This is required for example when copying an AAC stream from a raw ADTS
       AAC container to a FLV or a MOV/MP4 file.

   chomp
       Remove zero padding at the end of a packet.

   dump_extra
       Add extradata to the beginning of the filtered packets.

       The additional argument specifies which packets should be filtered.  It
       accepts the values:

       a   add extradata to all key packets, but only if local_header is set
	   in the flags2 codec context field

       k   add extradata to all key packets

       e   add extradata to all packets

       If not specified it is assumed k.

       For example the following ffmpeg command forces a global header (thus
       disabling individual packet headers) in the H.264 packets generated by
       the "libx264" encoder, but corrects them by adding the header stored in
       extradata to the key packets:

	       ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts

   dca_core
       Extract DCA core from DTS-HD streams.

   h264_mp4toannexb
       Convert an H.264 bitstream from length prefixed mode to start code
       prefixed mode (as defined in the Annex B of the ITU-T H.264
       specification).

       This is required by some streaming formats, typically the MPEG-2
       transport stream format ("mpegts").

       For example to remux an MP4 file containing an H.264 stream to mpegts
       format with ffmpeg, you can use the command:

	       ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts

   imxdump
       Modifies the bitstream to fit in MOV and to be usable by the Final Cut
       Pro decoder. This filter only applies to the mpeg2video codec, and is
       likely not needed for Final Cut Pro 7 and newer with the appropriate
       -tag:v.

       For example, to remux 30 MB/sec NTSC IMX to MOV:

	       ffmpeg -i input.mxf -c copy -bsf:v imxdump -tag:v mx3n output.mov

   mjpeg2jpeg
       Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.

       MJPEG is a video codec wherein each video frame is essentially a JPEG
       image. The individual frames can be extracted without loss, e.g. by

	       ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg

       Unfortunately, these chunks are incomplete JPEG images, because they
       lack the DHT segment required for decoding. Quoting from
       <http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml>:

       Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
       commented that "MJPEG, or at least the MJPEG in AVIs having the MJPG
       fourcc, is restricted JPEG with a fixed -- and *omitted* -- Huffman
       table. The JPEG must be YCbCr colorspace, it must be 4:2:2, and it must
       use basic Huffman encoding, not arithmetic or progressive. . . . You
       can indeed extract the MJPEG frames and decode them with a regular JPEG
       decoder, but you have to prepend the DHT segment to them, or else the
       decoder won't have any idea how to decompress the data. The exact table
       necessary is given in the OpenDML spec."

       This bitstream filter patches the header of frames extracted from an
       MJPEG stream (carrying the AVI1 header ID and lacking a DHT segment) to
       produce fully qualified JPEG images.

	       ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
	       exiftran -i -9 frame*.jpg
	       ffmpeg -i frame_%d.jpg -c:v copy rotated.avi

   mjpega_dump_header
   movsub
   mp3_header_decompress
   mpeg4_unpack_bframes
       Unpack DivX-style packed B-frames.

       DivX-style packed B-frames are not valid MPEG-4 and were only a
       workaround for the broken Video for Windows subsystem.  They use more
       space, can cause minor AV sync issues, require more CPU power to decode
       (unless the player has some decoded picture queue to compensate the
       2,0,2,0 frame per packet style) and cause trouble if copied into a
       standard container like mp4 or mpeg-ps/ts, because MPEG-4 decoders may
       not be able to decode them, since they are not valid MPEG-4.

       For example to fix an AVI file containing an MPEG-4 stream with DivX-
       style packed B-frames using ffmpeg, you can use the command:

	       ffmpeg -i INPUT.avi -codec copy -bsf:v mpeg4_unpack_bframes OUTPUT.avi

   noise
       Damages the contents of packets without damaging the container. Can be
       used for fuzzing or testing error resilience/concealment.

       Parameters: A numeral string, whose value is related to how often
       output bytes will be modified. Therefore, values below or equal to 0
       are forbidden, and the lower the more frequent bytes will be modified,
       with 1 meaning every byte is modified.

	       ffmpeg -i INPUT -c copy -bsf noise[=1] output.mkv

       applies the modification to every byte.

   remove_extra
SEE ALSO
       ffmpeg(1), ffplay(1), ffprobe(1), ffserver(1), libavcodec(3)

AUTHORS
       The FFmpeg developers.

       For details about the authorship, see the Git history of the project
       (git://source.ffmpeg.org/ffmpeg), e.g. by typing the command git log in
       the FFmpeg source directory, or browsing the online repository at
       <http://source.ffmpeg.org>.

       Maintainers for the specific components are listed in the file
       MAINTAINERS in the source code tree.

						   FFMPEG-BITSTREAM-FILTERS(1)
