[FFmpeg-devel] detecting MP3 content following ID3 tags over PROBE_BUF_MAX

Ami Fischman fischman at chromium.org
Mon Mar 19 19:42:18 CET 2012


>
> Hi Michael,

In a merge<http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=6faf0a21e18f314c48a886864145abe715be6572>
you
removed the effect of a
patch<http://git.libav.org/?p=libav.git;a=commit;f=libavformat/utils.c;h=61856d06eb30955290911140e6745bad93a25323>
by
Alex Converse which encouraged identification as mp3 of files with leading
ID3 tags that are so large as to prevent direct identification within the
first PROBE_BUF_MAX bytes.
Can you describe the reasons for the removal?

This came up in the context of a chrome bug <http://crbug.com/110309> report
with users complaining that certain MP3's encoded with large album artwork
in ID3 tags fail to play in chrome.
The same file plays fine in ffplay if it's named with an mp3 extension, but
not otherwise (since probing fails).

Although ID3 tags are not exclusive to MP3, it seems like a reasonable
guess to make in the absence of higher-scoring probe matches given the
distribution of ID3 tags in files in the wild, no?

Cheers,
 -a


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