[FFmpeg-devel] [PATCH 0/5] Fix mp3 gapless support (second try)

[Michael Niedermayer]

On Wed, Apr 15, 2015 at 11:08:02AM +0200, wm4 wrote:
> On Tue, 14 Apr 2015 22:44:22 +0200
> Michael Niedermayer <michaelni at gmx.at> wrote:
> 
> > On Tue, Apr 14, 2015 at 09:24:32PM +0200, wm4 wrote:
> > > Seeking was slightly broken. The 4th patch seems to fix this (everything
> > > else is noise).
> > > 
> > 
> > > Note that ffmpeg can't correctly implement mp3 gapless audio if seeking
> > > is used. The xing toc is not precise enough. The only way to fix it is
> > > to do a full scan on the mp3 to index each frame (which in turn is not
> > > possible with the public API, because byte seeking is not supported and
> > > the parser would interfere anyway). But in this case, it even broke when
> > > seeking to the beginning. I'm still not sure if this patch is correct.
> > 
> > do you have a file/sample/testcase for patch 4 ?
> 
> https://0x0.st/AG.mp3
> 
> I'm assuming mpg123 is getting it right. One test case is seeking to
> the start of the file. (Seeking to anywhere else likely won't work,
> because libavformat tries to use the imperfect xing toc, instead of
> scanning the frames.)

how can this be tested ?
./ffmpeg -ss 0 -i AG.mp3  -flags +bitexact new.wav
./ffmpeg-ref -ss 0 -i AG.mp3  -flags +bitexact old.wav

52298dcb38185e665b1b6d184884dd3e  new.wav
52298dcb38185e665b1b6d184884dd3e  old.wav

./ffmpeg -ss 5 -i AG.mp3  -flags +bitexact new.wav
./ffmpeg-ref -ss 5 -i AG.mp3  -flags +bitexact old.wav

b4b8f2a83924b48f3d25baa6b9b4f4a8  new.wav
b4b8f2a83924b48f3d25baa6b9b4f4a8  old.wav


[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I am the wisest man alive, for I know one thing, and that is that I know
nothing. -- Socrates
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