[Ffmpeg-devel] [PATCH] allow ffmpeg to read mp3s beginning with partial frames

Victor Voros Victor.Voros
Fri Sep 8 00:08:15 CEST 2006

 <<differences>> Comments below

-----Original Message-----
From: ffmpeg-devel-bounces at mplayerhq.hu
[mailto:ffmpeg-devel-bounces at mplayerhq.hu] On Behalf Of Michael
Sent: 07 September 2006 00:35
To: FFMpeg development discussions and patches
Subject: Re: [Ffmpeg-devel] [PATCH] allow ffmpeg to read mp3s beginning
with partial frames


On Thu, Sep 07, 2006 at 12:05:04AM +0100, Victor Voros wrote:
> Hi this is the first time im posting here  so apologies if format is
> wrong etc.
> Some mp3s I have begin with partial frames before the first
> Sync frame. WMP and ITunes handle them OK but SVN FFmpeg does not. Can
> send several examples of mp3 files that are like this.

yes, a sample which shows the problem would be needed

3 samples at

> Attached is a patch to libavformat\mp3.c which addresses this in diff
> format from head (6180)
> Simply scans the file looking for a sync frame and starts there if
> found.

rejected, this does not belong in libavformat, demuxers should output
whats in the file, not do codec specific parsing and discarding of stuff
such code should be in the parser or decoder

mp3.c as I see it serves 2 purposes, 1) to determine whether the file is
in fact an mp3 file (mp3_Read_probe) and 2) to prime the file so its
pointing at the start of the first frame, (currently skipping a possible
id3 tag) ready for the codec to do its work(mp3_read_header). The file
already has code to search for a valid mpeg frame sync, the change
expands on this by not assuming the frame sync is at the very start of
the file. No extra codec 'knowledge' has been added to this file.

In any case, mp3_read_probe is the routine rejecting the said files. One
way or another this has to change to accommodate the files. 

furthermore, the line endings in your patch look bad

try attached. 

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

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