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109 lines
4.0 KiB
Plaintext
109 lines
4.0 KiB
Plaintext
@chapter Demuxers
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@c man begin DEMUXERS
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Demuxers are configured elements in FFmpeg which allow to read the
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multimedia streams from a particular type of file.
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When you configure your FFmpeg build, all the supported demuxers
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are enabled by default. You can list all available ones using the
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configure option "--list-demuxers".
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You can disable all the demuxers using the configure option
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"--disable-demuxers", and selectively enable a single demuxer with
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the option "--enable-demuxer=@var{DEMUXER}", or disable it
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with the option "--disable-demuxer=@var{DEMUXER}".
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The option "-formats" of the ff* tools will display the list of
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enabled demuxers.
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The description of some of the currently available demuxers follows.
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@section image2
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Image file demuxer.
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This demuxer reads from a list of image files specified by a pattern.
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The pattern may contain the string "%d" or "%0@var{N}d", which
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specifies the position of the characters representing a sequential
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number in each filename matched by the pattern. If the form
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"%d0@var{N}d" is used, the string representing the number in each
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filename is 0-padded and @var{N} is the total number of 0-padded
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digits representing the number. The literal character '%' can be
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specified in the pattern with the string "%%".
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If the pattern contains "%d" or "%0@var{N}d", the first filename of
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the file list specified by the pattern must contain a number
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inclusively contained between 0 and 4, all the following numbers must
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be sequential. This limitation may be hopefully fixed.
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The pattern may contain a suffix which is used to automatically
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determine the format of the images contained in the files.
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For example the pattern "img-%03d.bmp" will match a sequence of
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filenames of the form @file{img-001.bmp}, @file{img-002.bmp}, ...,
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@file{img-010.bmp}, etc.; the pattern "i%%m%%g-%d.jpg" will match a
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sequence of filenames of the form @file{i%m%g-1.jpg},
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@file{i%m%g-2.jpg}, ..., @file{i%m%g-10.jpg}, etc.
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The size, the pixel format, and the format of each image must be the
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same for all the files in the sequence.
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The following example shows how to use @command{ffmpeg} for creating a
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video from the images in the file sequence @file{img-001.jpeg},
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@file{img-002.jpeg}, ..., assuming an input frame rate of 10 frames per
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second:
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@example
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ffmpeg -i 'img-%03d.jpeg' -r 10 out.mkv
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@end example
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Note that the pattern must not necessarily contain "%d" or
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"%0@var{N}d", for example to convert a single image file
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@file{img.jpeg} you can employ the command:
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@example
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ffmpeg -i img.jpeg img.png
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@end example
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@section applehttp
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Apple HTTP Live Streaming demuxer.
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This demuxer presents all AVStreams from all variant streams.
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The id field is set to the bitrate variant index number. By setting
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the discard flags on AVStreams (by pressing 'a' or 'v' in ffplay),
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the caller can decide which variant streams to actually receive.
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The total bitrate of the variant that the stream belongs to is
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available in a metadata key named "variant_bitrate".
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@section sbg
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SBaGen script demuxer.
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This demuxer reads the script language used by SBaGen
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@url{http://uazu.net/sbagen/} to generate binaural beats sessions. A SBG
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script looks like that:
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@example
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-SE
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a: 300-2.5/3 440+4.5/0
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b: 300-2.5/0 440+4.5/3
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off: -
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NOW == a
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+0:07:00 == b
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+0:14:00 == a
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+0:21:00 == b
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+0:30:00 off
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@end example
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A SBG script can mix absolute and relative timestamps. If the script uses
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either only absolute timestamps (including the script start time) or only
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relative ones, then its layout is fixed, and the conversion is
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straightforward. On the other hand, if the script mixes both kind of
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timestamps, then the @var{NOW} reference for relative timestamps will be
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taken from the current time of day at the time the script is read, and the
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script layout will be frozen according to that reference. That means that if
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the script is directly played, the actual times will match the absolute
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timestamps up to the sound controller's clock accuracy, but if the user
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somehow pauses the playback or seeks, all times will be shifted accordingly.
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@c man end INPUT DEVICES
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