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doc: reword the mp3 muxer documentation

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Make it more structured.
This commit is contained in:
Anton Khirnov 2014-04-12 15:20:01 +02:00
parent 99143140de
commit c63418e0a3
1 changed files with 24 additions and 16 deletions
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doc/muxers.texi
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@ -347,29 +347,37 @@ avconv -re @var{<normal input/transcoding options>} -movflags isml+frag_keyframe
@section mp3
The MP3 muxer writes a raw MP3 stream with an ID3v2 header at the beginning and
optionally an ID3v1 tag at the end. ID3v2.3 and ID3v2.4 are supported, the
@code{id3v2_version} option controls which one is used. Setting
@code{id3v2_version} to 0 will disable the ID3v2 header completely. The legacy
ID3v1 tag is not written by default, but may be enabled with the
@code{write_id3v1} option.
The MP3 muxer writes a raw MP3 stream with the following optional features:
@itemize @bullet
@item
An ID3v2 metadata header at the beginning (enabled by default). Versions 2.3 and
2.4 are supported, the @code{id3v2_version} private option controls which one is
used (3 or 4). Setting @code{id3v2_version} to 0 disables the ID3v2 header
completely.
The muxer may also write a Xing frame at the beginning, which contains the
number of frames in the file. It is useful for computing duration of VBR files.
The Xing frame is written if the output stream is seekable and if the
@code{write_xing} option is set to 1 (the default).
The muxer supports writing ID3v2 attached pictures (APIC frames). The pictures
are supplied to the muxer in form of a video stream with a single packet. There
can be any number of those streams, each will correspond to a single APIC frame.
The stream metadata tags @var{title} and @var{comment} map to APIC
@var{description} and @var{picture type} respectively. See
The muxer supports writing attached pictures (APIC frames) to the ID3v2 header.
The pictures are supplied to the muxer in form of a video stream with a single
packet. There can be any number of those streams, each will correspond to a
single APIC frame. The stream metadata tags @var{title} and @var{comment} map
to APIC @var{description} and @var{picture type} respectively. See
@url{http://id3.org/id3v2.4.0-frames} for allowed picture types.
Note that the APIC frames must be written at the beginning, so the muxer will
buffer the audio frames until it gets all the pictures. It is therefore advised
to provide the pictures as soon as possible to avoid excessive buffering.
@item
A Xing/LAME frame right after the ID3v2 header (if present). It is enabled by
default, but will be written only if the output is seekable. The
@code{write_xing} private option can be used to disable it. The frame contains
various information that may be useful to the decoder, like the audio duration.
@item
A legacy ID3v1 tag at the end of the file (disabled by default). It may be
enabled with the @code{write_id3v1} private option, but as its capabilities are
very limited, its usage is not recommended.
@end itemize
Examples:
Write an mp3 with an ID3v2.3 header and an ID3v1 footer: