[FFmpeg-devel] Error in ATRAC1 decoder?

[Даниил Чередник]

I rechecked it.
The issue with test is the test uses decoded from aea sample pcm file. And
it looks like this file is not correctly decoded (it is easy to see at
0.7221 sec, https://yadi.sk/i/8WBO701XkcHUv). Same place decoded by fixed
version is https://yadi.sk/i/efG3lkEGkcHYE.

Also I made test with newly encoded ATRAC1 file. I included source pcm and
encoded aea in to the fate test. These files are here
https://yadi.sk/d/DA-xxzM_kcJ5t



On Wed, Nov 18, 2015 at 10:19 PM, Michael Niedermayer <michaelni at gmx.at>
wrote:

> On Tue, Nov 17, 2015 at 04:08:29AM +0300, Даниил Чередник wrote:
> > Thank you for answer.
> >
> > If I understood available ATRAC1 docs, the purpose of this delay line is
> > just to compensate delay of 1st QMF because for 1st and 2nd band we have
> > two QMF but for 3rd band just one.
> >
> > About test, yes for some reason this patch brakes it. I will try to find
> > out. Sorry, I should have done it before.
>
> np
> if the changed / new version is more correct then please also provide
> a new reference file for the fate samples with a new filename and
> update the fate test so it uses the new file
>
> thanks
>
> >
> > I tried to decode "The Four Seasons, Concerto Alla Rustica in G - Winter-
> > Largo.aea" sample, the results are:
> > without patch: https://yadi.sk/i/PCFplrafkWEFC
> > with patch: https://yadi.sk/i/iLUR188gkWEFn
> > On zoomed spectrogram it is possible to find aliasing if decode without
> > patch. I can share decoded wav file if needed.
> >
> >
> >
> > On Mon, Nov 16, 2015 at 3:45 AM, Michael Niedermayer
> <michael at niedermayer.cc
> > > wrote:
> >
> > > On Sat, Nov 14, 2015 at 02:59:30AM +0300, Даниил Чередник wrote:
> > > > Hello!
> > > >
> > > > I have noticed if decode
> > > >
> > >
> https://samples.ffmpeg.org/A-codecs/ATRAC1/Test%20tones%20disc%20-%20Chirp.aea
> > > > file by ffmpeg we got aliasing near 11025Hz. Screenshots:
> > > > https://yadi.sk/i/r-95jZkKkSnbu https://yadi.sk/i/PV92LNESkSnby
> > > >
> > > > I was tried to solve it:
> > > >
> > > > ATRAC1 - hybrid codec, has two stacked QMF and splits the signal
> into 3
> > > > band before MDCT. Thereby we need to compensate delay of one QMF to
> > > > achieve reconstruction.
> > > > There is a delay line but it looks like delay for 23 sample is not
> > > correct.
> > > > I have done some experiments and got 39 should be right delay.
> Results of
> > > > decoding with patch: https://yadi.sk/i/yooaIQrmkSncB
> > > > https://yadi.sk/i/CUXsH7-CkSncK
> > > >
> > >
> > > > To be honest I am not a prof in math and it would be great if someone
> > > > recheck it from math perspective.
> > >
> > > i dont think math can help here
> > > whatever a format requires that has to be done, this could even be
> > > wrong from a math point of view of a ideal transform
> > >
> > >
> > > >
> > > > There is a patch in attach.
> > >
> > > the patch also affects the atrac1 fate test
> > > have you checked if the new output for that test is better than the
> > > old ?
> > >
> > > make V=2 fate-atrac1
> > >
> > > also have you looked at other files, is this improving all files ?
> > > any that get worse ?
> > >
> > >
> > > [...]
> > >
> > > --
> > > Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
> > >
> > > Many that live deserve death. And some that die deserve life. Can you
> give
> > > it to them? Then do not be too eager to deal out death in judgement.
> For
> > > even the very wise cannot see all ends. -- Gandalf
> > >
> > > _______________________________________________
> > > ffmpeg-devel mailing list
> > > ffmpeg-devel at ffmpeg.org
> > > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> > >
> > >
> >
> >
> > --
> > Daniil Cherednik
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> The greatest way to live with honor in this world is to be what we pretend
> to be. -- Socrates
>
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>


-- 
Daniil Cherednik
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