[deb_ffmpeg.git] / ffmpeg / doc / bitstream_filters.texi

@chapter Bitstream Filters
@c man begin 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 @code{--list-bsfs}.

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

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

Below is a description of the currently available bitstream filters.

@section 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.

@section chomp

Remove zero padding at the end of a packet.

@section dump_extra

Add extradata to the beginning of the filtered packets.

The additional argument specifies which packets should be filtered.
It accepts the values:
@table @samp
@item a
add extradata to all key packets, but only if @var{local_header} is
set in the @option{flags2} codec context field

@item k
add extradata to all key packets

@item e
add extradata to all packets
@end table

If not specified it is assumed @samp{k}.

For example the following @command{ffmpeg} command forces a global
header (thus disabling individual packet headers) in the H.264 packets
generated by the @code{libx264} encoder, but corrects them by adding
the header stored in extradata to the key packets:
@example
ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts
@end example

@section 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 @command{ffmpeg}, you can use the command:

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

@section 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
@option{-tag:v}.

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

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

@section 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

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

Unfortunately, these chunks are incomplete JPEG images, because
they lack the DHT segment required for decoding. Quoting from
@url{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.

@example
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
@end example

@section mjpega_dump_header

@section movsub

@section mp3_header_decompress

@section noise

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

@example
ffmpeg -i INPUT -c copy -bsf noise output.mkv
@end example

@section remove_extra

@c man end BITSTREAM FILTERS
Commit	Line	Data
2ba45a60 DM	1	@chapter Bitstream Filters
	2	@c man begin BITSTREAM FILTERS
	3
	4	When you configure your FFmpeg build, all the supported bitstream
	5	filters are enabled by default. You can list all available ones using
	6	the configure option @code{--list-bsfs}.
	7
	8	You can disable all the bitstream filters using the configure option
	9	@code{--disable-bsfs}, and selectively enable any bitstream filter using
	10	the option @code{--enable-bsf=BSF}, or you can disable a particular
	11	bitstream filter using the option @code{--disable-bsf=BSF}.
	12
	13	The option @code{-bsfs} of the ff* tools will display the list of
	14	all the supported bitstream filters included in your build.
	15
	16	Below is a description of the currently available bitstream filters.
	17
	18	@section aac_adtstoasc
	19
	20	Convert MPEG-2/4 AAC ADTS to MPEG-4 Audio Specific Configuration
	21	bitstream filter.
	22
	23	This filter creates an MPEG-4 AudioSpecificConfig from an MPEG-2/4
	24	ADTS header and removes the ADTS header.
	25
	26	This is required for example when copying an AAC stream from a raw
	27	ADTS AAC container to a FLV or a MOV/MP4 file.
	28
	29	@section chomp
	30
	31	Remove zero padding at the end of a packet.
	32
	33	@section dump_extra
	34
	35	Add extradata to the beginning of the filtered packets.
	36
	37	The additional argument specifies which packets should be filtered.
	38	It accepts the values:
	39	@table @samp
	40	@item a
	41	add extradata to all key packets, but only if @var{local_header} is
	42	set in the @option{flags2} codec context field
	43
	44	@item k
	45	add extradata to all key packets
	46
	47	@item e
	48	add extradata to all packets
	49	@end table
	50
	51	If not specified it is assumed @samp{k}.
	52
	53	For example the following @command{ffmpeg} command forces a global
	54	header (thus disabling individual packet headers) in the H.264 packets
	55	generated by the @code{libx264} encoder, but corrects them by adding
	56	the header stored in extradata to the key packets:
	57	@example
	58	ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts
	59	@end example
	60
	61	@section h264_mp4toannexb
	62
	63	Convert an H.264 bitstream from length prefixed mode to start code
	64	prefixed mode (as defined in the Annex B of the ITU-T H.264
65	specification).
66
67	This is required by some streaming formats, typically the MPEG-2
68	transport stream format ("mpegts").
69
70	For example to remux an MP4 file containing an H.264 stream to mpegts
71	format with @command{ffmpeg}, you can use the command:
72
73	@example
74	ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts
75	@end example
76
77	@section imxdump
78
79	Modifies the bitstream to fit in MOV and to be usable by the Final Cut
80	Pro decoder. This filter only applies to the mpeg2video codec, and is
81	likely not needed for Final Cut Pro 7 and newer with the appropriate
82	@option{-tag:v}.
83
84	For example, to remux 30 MB/sec NTSC IMX to MOV:
85
86	@example
87	ffmpeg -i input.mxf -c copy -bsf:v imxdump -tag:v mx3n output.mov
88	@end example
89
90	@section mjpeg2jpeg
91
92	Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
93
94	MJPEG is a video codec wherein each video frame is essentially a
95	JPEG image. The individual frames can be extracted without loss,
96	e.g. by
97
98	@example
99	ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
100	@end example
101
102	Unfortunately, these chunks are incomplete JPEG images, because
103	they lack the DHT segment required for decoding. Quoting from
104	@url{http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml}:
105
106	Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
107	commented that "MJPEG, or at least the MJPEG in AVIs having the
108	MJPG fourcc, is restricted JPEG with a fixed -- and omitted --
109	Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2,
110	and it must use basic Huffman encoding, not arithmetic or
111	progressive. . . . You can indeed extract the MJPEG frames and
112	decode them with a regular JPEG decoder, but you have to prepend
113	the DHT segment to them, or else the decoder won't have any idea
114	how to decompress the data. The exact table necessary is given in
115	the OpenDML spec."
116
117	This bitstream filter patches the header of frames extracted from an MJPEG
118	stream (carrying the AVI1 header ID and lacking a DHT segment) to
119	produce fully qualified JPEG images.
120
121	@example
122	ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
123	exiftran -i -9 frame*.jpg
124	ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
125	@end example
126
127	@section mjpega_dump_header
128
129	@section movsub
130
131	@section mp3_header_decompress
132
133	@section noise
134
135	Damages the contents of packets without damaging the container. Can be
136	used for fuzzing or testing error resilience/concealment.
137
138	@example
139	ffmpeg -i INPUT -c copy -bsf noise output.mkv
140	@end example
141
142	@section remove_extra
143
144	@c man end BITSTREAM FILTERS