Enabling MP3 support in vlc

Christophe Massiot massiot at via.ecp.fr
Mon Feb 4 23:31:57 CET 2002

À (At) 23:02 +0100 3/02/02, Jean-Paul Saman écrivait (wrote) :

>Almost every mp3 file is built up of IDv3 tags and MPEG frames. It
>starts with "ID3" followed by approximately 96 bytes of header data (see
>www.id3.org). This information is only of interest to audio players and
>user interfaces in general.
>The so called ID3 tags are only found at the begining and the end of an
>mp3 file. They provide title, author and could even contain song lyrics.
>In short nothing to do with the decoder.

This is quite interesting. Does libmad provide functions to parse the 
ID3 tags ? Are the tags always at the end of the file (how do you do 
then when you stream mp3 ?) ?

>Where do you exactly detect that a stream is of type MPEG1_AUDIO_ES?
>There should audio layer III be detected along side layer I and II in
>SelectES file input_programs. Which variable in p_es tells it the data
>is one of the layers? And in which code is that detected?

Don't confuse things. MPEG1_AUDIO_ES == MPEG-1 (ISO/IEC 11172-3), 
MPEG2_AUDIO_ES == MPEG-2 (ISO/IEC 13818-3), there is absolutely NO 
notion of layer in this. For a simple reason : the input layer can't 
tell the layer of the audio stream without looking inside, that's the 
job of the decoder.

What will probably happen in the long run is that libmad will always 
be used, so we don't need to indicate that layer (libmad can read all 

Christophe Massiot.

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