[FFmpeg-devel] Review request - ra288.{c,h} ra144.{c,h}

Siarhei Siamashka siarhei.siamashka
Sun Sep 14 18:50:03 CEST 2008


On Sunday 14 September 2008, Vitor Sessak wrote:
> Michael Niedermayer wrote:
[...]
> > If you want a proof that it is better, you should compare the original
> > pcm that is
> >
> > X -> encoder -> binary decoder -> Y
> >              -> FF decoder ->Z
> >
> > and look at how the X-Y and X-Z change relative to each other.
> >
> > Also you would see a similar PSNR change relative to the binary decoder
> > if you would output floats.
>
> I've already tried comparing PSNR to the original input when I was
> looking for a way to test float codecs in FATE.
>
> vitor at vitor$ ffmpeg -i luckynightmono2.ra -ac 1 -ar 8000 test.wav
> vitor at vitor$ ffmpeg -i luckynight.wav -ac 1 -ar 8000 test2.wav
> vitor at vitor$ tiny_psnr test.wav test2.wav 2 0 44
> stddev: 5981.39 PSNR: 20.78 bytes:   990720/   967662
> vitor at vitor$ tiny_psnr test.wav test2.wav 2 2 44
> stddev: 5982.77 PSNR: 20.78 bytes:   990718/   967662
> vitor at vitor$ tiny_psnr test.wav test2.wav 2 100 44
> stddev: 6012.76 PSNR: 20.74 bytes:   990620/   967662
>
> And by looking at results, if I change the "skip bytes" parameter I
> don't get much change in PSNR. For me, this is a signal that the value I
> got is meaningless (since it don't change a lot if I compare it with
> different data). I asked about it in IRC and people told me that PSNR
> didn't worked very well to LPC vocoders. Sample in
> http://samples.mplayerhq.hu/real/AC-28_8/ .

You can try this patch for tiny_psnr, I'm using it in my experiments with
audio decoding. See
http://thread.gmane.org/gmane.comp.video.ffmpeg.devel/37796/focus=38052
and
http://article.gmane.org/gmane.comp.video.ffmpeg.devel/74535/

Don't know if it helps you, but I find it quite useful. For example, ffvorbis
decoder produces inverted output and standard tiny_psnr can't be used to
compare it with libvorbis output (it just can't see anything common in the
files and reports a horrible PSNR with the numbers similar to what you got).

-- 
Best regards,
Siarhei Siamashka
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