aac5773f
 hucm
功能基本完成，接口待打磨
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@chapter Metadata
@c man begin METADATA
FFmpeg is able to dump metadata from media files into a simple UTF-8-encoded
INI-like text file and then load it back using the metadata muxer/demuxer.
The file format is as follows:
@enumerate
@item
A file consists of a header and a number of metadata tags divided into sections,
each on its own line.
@item
The header is a @samp{;FFMETADATA} string, followed by a version number (now 1).
@item
Metadata tags are of the form @samp{key=value}
@item
Immediately after header follows global metadata
@item
After global metadata there may be sections with per-stream/per-chapter
metadata.
@item
A section starts with the section name in uppercase (i.e. STREAM or CHAPTER) in
brackets (@samp{[}, @samp{]}) and ends with next section or end of file.
@item
At the beginning of a chapter section there may be an optional timebase to be
used for start/end values. It must be in form
@samp{TIMEBASE=@var{num}/@var{den}}, where @var{num} and @var{den} are
integers. If the timebase is missing then start/end times are assumed to
be in nanoseconds.
Next a chapter section must contain chapter start and end times in form
@samp{START=@var{num}}, @samp{END=@var{num}}, where @var{num} is a positive
integer.
@item
Empty lines and lines starting with @samp{;} or @samp{#} are ignored.
@item
Metadata keys or values containing special characters (@samp{=}, @samp{;},
@samp{#}, @samp{\} and a newline) must be escaped with a backslash @samp{\}.
@item
Note that whitespace in metadata (e.g. @samp{foo = bar}) is considered to be
a part of the tag (in the example above key is @samp{foo }, value is
@samp{ bar}).
@end enumerate
A ffmetadata file might look like this:
@example
;FFMETADATA1
title=bike\\shed
;this is a comment
artist=FFmpeg troll team
[CHAPTER]
TIMEBASE=1/1000
START=0
#chapter ends at 0:01:00
END=60000
title=chapter \#1
[STREAM]
title=multi\
line
@end example
By using the ffmetadata muxer and demuxer it is possible to extract
metadata from an input file to an ffmetadata file, and then transcode
the file into an output file with the edited ffmetadata file.
Extracting an ffmetadata file with @file{ffmpeg} goes as follows:
@example
ffmpeg -i INPUT -f ffmetadata FFMETADATAFILE
@end example
Reinserting edited metadata information from the FFMETADATAFILE file can
be done as:
@example
ffmpeg -i INPUT -i FFMETADATAFILE -map_metadata 1 -codec copy OUTPUT
@end example
@c man end METADATA
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