Add documentation for the crc muxer.
[libav.git] / doc / muxers.texi
1 @chapter Muxers
2 @c man begin MUXERS
4 Muxers are configured elements in FFmpeg which allow writing
5 multimedia streams to a particular type of file.
7 When you configure your FFmpeg build, all the supported muxers
8 are enabled by default. You can list all available muxers using the
9 configure option @code{--list-muxers}.
11 You can disable all the muxers with the configure option
12 @code{--disable-muxers} and selectively enable / disable single muxers
13 with the options @code{--enable-muxer=@var{MUXER}} /
14 @code{--disable-muxer=@var{MUXER}}.
16 The option @code{-formats} of the ff* tools will display the list of
17 enabled muxers.
19 A description of some of the currently available muxers follows.
21 @section crc
23 CRC (Cyclic Redundancy Check) testing format.
25 This muxer computes and prints the Adler-32 CRC of all the input audio
26 and video frames. By default audio frames are converted to signed
27 16-bit raw audio and video frames to raw video before computing the
28 CRC.
30 The output of the muxer consists of a single line of the form:
31 CRC=0x@var{CRC}, where @var{CRC} is a hexadecimal number 0-padded to
32 8 digits containing the CRC for all the decoded input frames.
34 For example to compute the CRC of the input, and store it in the file
35 @file{out.crc}:
36 @example
37 ffmpeg -i INPUT -f crc out.crc
38 @end example
40 You can print the CRC to stdout with the command:
41 @example
42 ffmpeg -i INPUT -f crc -
43 @end example
45 You can select the output format of each frame with @file{ffmpeg} by
46 specifying the audio and video codec and format. For example to
47 compute the CRC of the input audio converted to PCM unsigned 8-bit
48 and the input video converted to MPEG-2 video, use the command:
49 @example
50 ffmpeg -i INPUT -acodec pcm_u8 -vcodec mpeg2video -f crc -
51 @end example
53 @section image2
55 Image file muxer.
57 This muxer writes video frames to multiple image files specified by a
58 pattern.
60 The pattern may contain the string "%d" or "%0@var{N}d", which
61 specifies the position of the characters representing a numbering in
62 the filenames. If the form "%d0@var{N}d" is used, the string
63 representing the number in each filename is 0-padded to @var{N}
64 digits. The literal character '%' can be specified in the pattern with
65 the string "%%".
67 If the pattern contains "%d" or "%0@var{N}d", the first filename of
68 the file list specified will contain the number 1, all the following
69 numbers will be sequential.
71 The pattern may contain a suffix which is used to automatically
72 determine the format of the image files to write.
74 For example the pattern "img-%03d.bmp" will specify a sequence of
75 filenames of the form @file{img-001.bmp}, @file{img-002.bmp}, ...,
76 @file{img-010.bmp}, etc.
77 The pattern "img%%-%d.jpg" will specify a sequence of filenames of the
78 form @file{img%-1.jpg}, @file{img%-2.jpg}, ..., @file{img%-10.jpg},
79 etc.
81 The following example shows how to use @file{ffmpeg} for creating a
82 sequence of files @file{img-001.jpeg}, @file{img-002.jpeg}, ...,
83 taking one image every second from the input video:
84 @example
85 ffmpeg -i in.avi -r 1 -f image2 'img-%03d.jpeg'
86 @end example
88 Note that with @file{ffmpeg}, if the format is not specified with the
89 @code{-f} option and the output filename specifies an image file
90 format, the image2 muxer is automatically selected, so the previous
91 command can be written as:
92 @example
93 ffmpeg -i in.avi -r 1 'img-%03d.jpeg'
94 @end example
96 Note also that the pattern must not necessarily contain "%d" or
97 "%0@var{N}d", for example to create a single image file
98 @file{img.jpeg} from the input video you can employ the command:
99 @example
100 ffmpeg -i in.avi -f image2 -vframes 1 img.jpeg
101 @end example
103 @section mpegts
105 MPEG transport stream muxer.
107 This muxer implements ISO 13818-1 and part of ETSI EN 300 468.
109 The muxer options are:
111 @table @option
112 @item -mpegts_original_network_id @var{number}
113 Set the original_network_id (default 0x0001). This is unique identifier
114 of a network in DVB. Its main use is in the unique identification of a
115 service through the path Original_Network_ID, Transport_Stream_ID.
116 @item -mpegts_transport_stream_id @var{number}
117 Set the transport_stream_id (default 0x0001). This identifies a
118 transponder in DVB.
119 @item -mpegts_service_id @var{number}
120 Set the service_id (default 0x0001) also known as program in DVB.
121 @item -mpegts_pmt_start_pid @var{number}
122 Set the first PID for PMT (default 0x1000, max 0x1f00).
123 @item -mpegts_start_pid @var{number}
124 Set the first PID for data packets (default 0x0100, max 0x0f00).
125 @end table
127 The recognized metadata settings in mpegts muxer are @code{service_provider}
128 and @code{service_name}. If they are not set the default for
129 @code{service_provider} is "FFmpeg" and the default for
130 @code{service_name} is "Service01".
132 @example
133 ffmpeg -i file.mpg -acodec copy -vcodec copy \
134 -mpegts_original_network_id 0x1122 \
135 -mpegts_transport_stream_id 0x3344 \
136 -mpegts_service_id 0x5566 \
137 -mpegts_pmt_start_pid 0x1500 \
138 -mpegts_start_pid 0x150 \
139 -metadata service_provider="Some provider" \
140 -metadata service_name="Some Channel" \
141 -y out.ts
142 @end example
144 @section null
146 Null muxer.
148 This muxer does not generate any output file, it is mainly useful for
149 testing or benchmarking purposes.
151 For example to benchmark decoding with @file{ffmpeg} you can use the
152 command:
153 @example
154 ffmpeg -benchmark -i INPUT -f null out.null
155 @end example
157 Note that the above command does not read or write the @file{out.null}
158 file, but specifying the output file is required by the @file{ffmpeg}
159 syntax.
161 Alternatively you can write the command as:
162 @example
163 ffmpeg -benchmark -i INPUT -f null -
164 @end example
166 @c man end MUXERS