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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	The ff* tools have a -bsf option applied per stream, taking a
17	comma-separated list of filters, whose parameters follow the filter
18	name after a '='.
19
20	@example
21	ffmpeg -i INPUT -c:v copy -bsf:v filter1[=opt1=str1:opt2=str2][,filter2] OUTPUT
22	@end example
23
24	Below is a description of the currently available bitstream filters,
25	with their parameters, if any.
26
27	@section aac_adtstoasc
28
29	Convert MPEG-2/4 AAC ADTS to an MPEG-4 Audio Specific Configuration
30	bitstream.
31
32	This filter creates an MPEG-4 AudioSpecificConfig from an MPEG-2/4
33	ADTS header and removes the ADTS header.
34
35	This filter is required for example when copying an AAC stream from a
36	raw ADTS AAC or an MPEG-TS container to MP4A-LATM, to an FLV file, or
37	to MOV/MP4 files and related formats such as 3GP or M4A. Please note
38	that it is auto-inserted for MP4A-LATM and MOV/MP4 and related formats.
39
40	@section chomp
41
42	Remove zero padding at the end of a packet.
43
44	@section dca_core
45
46	Extract the core from a DCA/DTS stream, dropping extensions such as
47	DTS-HD.
48
49	@section dump_extra
50
51	Add extradata to the beginning of the filtered packets.
52
53	The additional argument specifies which packets should be filtered.
54	It accepts the values:
55	@table @samp
56	@item a
57	add extradata to all key packets, but only if @var{local_header} is
58	set in the @option{flags2} codec context field
59
60	@item k
61	add extradata to all key packets
62
63	@item e
64	add extradata to all packets
65	@end table
66
67	If not specified it is assumed @samp{k}.
68
69	For example the following @command{ffmpeg} command forces a global
70	header (thus disabling individual packet headers) in the H.264 packets
71	generated by the @code{libx264} encoder, but corrects them by adding
72	the header stored in extradata to the key packets:
73	@example
74	ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v dump_extra out.ts
75	@end example
76
77	@section extract_extradata
78
79	Extract the in-band extradata.
80
81	Certain codecs allow the long-term headers (e.g. MPEG-2 sequence headers,
82	or H.264/HEVC (VPS/)SPS/PPS) to be transmitted either "in-band" (i.e. as a part
83	of the bitstream containing the coded frames) or "out of band" (e.g. on the
84	container level). This latter form is called "extradata" in FFmpeg terminology.
85
86	This bitstream filter detects the in-band headers and makes them available as
87	extradata.
88
89	@table @option
90	@item remove
91	When this option is enabled, the long-term headers are removed from the
92	bitstream after extraction.
93	@end table
94
95	@section h264_mp4toannexb
96
97	Convert an H.264 bitstream from length prefixed mode to start code
98	prefixed mode (as defined in the Annex B of the ITU-T H.264
99	specification).
100
101	This is required by some streaming formats, typically the MPEG-2
102	transport stream format (muxer @code{mpegts}).
103
104	For example to remux an MP4 file containing an H.264 stream to mpegts
105	format with @command{ffmpeg}, you can use the command:
106
107	@example
108	ffmpeg -i INPUT.mp4 -codec copy -bsf:v h264_mp4toannexb OUTPUT.ts
109	@end example
110
111	Please note that this filter is auto-inserted for MPEG-TS (muxer
112	@code{mpegts}) and raw H.264 (muxer @code{h264}) output formats.
113
114	@section hevc_mp4toannexb
115
116	Convert an HEVC/H.265 bitstream from length prefixed mode to start code
117	prefixed mode (as defined in the Annex B of the ITU-T H.265
118	specification).
119
120	This is required by some streaming formats, typically the MPEG-2
121	transport stream format (muxer @code{mpegts}).
122
123	For example to remux an MP4 file containing an HEVC stream to mpegts
124	format with @command{ffmpeg}, you can use the command:
125
126	@example
127	ffmpeg -i INPUT.mp4 -codec copy -bsf:v hevc_mp4toannexb OUTPUT.ts
128	@end example
129
130	Please note that this filter is auto-inserted for MPEG-TS (muxer
131	@code{mpegts}) and raw HEVC/H.265 (muxer @code{h265} or
132	@code{hevc}) output formats.
133
134	@section imxdump
135
136	Modifies the bitstream to fit in MOV and to be usable by the Final Cut
137	Pro decoder. This filter only applies to the mpeg2video codec, and is
138	likely not needed for Final Cut Pro 7 and newer with the appropriate
139	@option{-tag:v}.
140
141	For example, to remux 30 MB/sec NTSC IMX to MOV:
142
143	@example
144	ffmpeg -i input.mxf -c copy -bsf:v imxdump -tag:v mx3n output.mov
145	@end example
146
147	@section mjpeg2jpeg
148
149	Convert MJPEG/AVI1 packets to full JPEG/JFIF packets.
150
151	MJPEG is a video codec wherein each video frame is essentially a
152	JPEG image. The individual frames can be extracted without loss,
153	e.g. by
154
155	@example
156	ffmpeg -i ../some_mjpeg.avi -c:v copy frames_%d.jpg
157	@end example
158
159	Unfortunately, these chunks are incomplete JPEG images, because
160	they lack the DHT segment required for decoding. Quoting from
161	@url{http://www.digitalpreservation.gov/formats/fdd/fdd000063.shtml}:
162
163	Avery Lee, writing in the rec.video.desktop newsgroup in 2001,
164	commented that "MJPEG, or at least the MJPEG in AVIs having the
165	MJPG fourcc, is restricted JPEG with a fixed -- and *omitted* --
166	Huffman table. The JPEG must be YCbCr colorspace, it must be 4:2:2,
167	and it must use basic Huffman encoding, not arithmetic or
168	progressive. . . . You can indeed extract the MJPEG frames and
169	decode them with a regular JPEG decoder, but you have to prepend
170	the DHT segment to them, or else the decoder won't have any idea
171	how to decompress the data. The exact table necessary is given in
172	the OpenDML spec."
173
174	This bitstream filter patches the header of frames extracted from an MJPEG
175	stream (carrying the AVI1 header ID and lacking a DHT segment) to
176	produce fully qualified JPEG images.
177
178	@example
179	ffmpeg -i mjpeg-movie.avi -c:v copy -bsf:v mjpeg2jpeg frame_%d.jpg
180	exiftran -i -9 frame*.jpg
181	ffmpeg -i frame_%d.jpg -c:v copy rotated.avi
182	@end example
183
184	@section mjpegadump
185
186	Add an MJPEG A header to the bitstream, to enable decoding by
187	Quicktime.
188
189	@anchor{mov2textsub}
190	@section mov2textsub
191
192	Extract a representable text file from MOV subtitles, stripping the
193	metadata header from each subtitle packet.
194
195	See also the @ref{text2movsub} filter.
196
197	@section mp3decomp
198
199	Decompress non-standard compressed MP3 audio headers.
200
201	@section mpeg4_unpack_bframes
202
203	Unpack DivX-style packed B-frames.
204
205	DivX-style packed B-frames are not valid MPEG-4 and were only a
206	workaround for the broken Video for Windows subsystem.
207	They use more space, can cause minor AV sync issues, require more
208	CPU power to decode (unless the player has some decoded picture queue
209	to compensate the 2,0,2,0 frame per packet style) and cause
210	trouble if copied into a standard container like mp4 or mpeg-ps/ts,
211	because MPEG-4 decoders may not be able to decode them, since they are
212	not valid MPEG-4.
213
214	For example to fix an AVI file containing an MPEG-4 stream with
215	DivX-style packed B-frames using @command{ffmpeg}, you can use the command:
216
217	@example
218	ffmpeg -i INPUT.avi -codec copy -bsf:v mpeg4_unpack_bframes OUTPUT.avi
219	@end example
220
221	@section noise
222
223	Damages the contents of packets without damaging the container. Can be
224	used for fuzzing or testing error resilience/concealment.
225
226	Parameters:
227	A numeral string, whose value is related to how often output bytes will
228	be modified. Therefore, values below or equal to 0 are forbidden, and
229	the lower the more frequent bytes will be modified, with 1 meaning
230	every byte is modified.
231
232	@example
233	ffmpeg -i INPUT -c copy -bsf noise[=1] output.mkv
234	@end example
235	applies the modification to every byte.
236
237	@section remove_extra
238
239	Remove extradata from packets.
240
241	It accepts the following parameter:
242	@table @option
243	@item freq
244	Set which frame types to remove extradata from.
245
246	@table @samp
247	@item k
248	Remove extradata from non-keyframes only.
249
250	@item keyframe
251	Remove extradata from keyframes only.
252
253	@item e, all
254	Remove extradata from all frames.
255
256	@end table
257	@end table
258
259	@anchor{text2movsub}
260	@section text2movsub
261
262	Convert text subtitles to MOV subtitles (as used by the @code{mov_text}
263	codec) with metadata headers.
264
265	See also the @ref{mov2textsub} filter.
266
267	@section vp9_superframe
268
269	Merge VP9 invisible (alt-ref) frames back into VP9 superframes. This
270	fixes merging of split/segmented VP9 streams where the alt-ref frame
271	was split from its visible counterpart.
272
273	@c man end BITSTREAM FILTERS
274