[Ffmpeg-devel] [PATCH] Shift autodetection for tiny_psnr.c

Siarhei Siamashka siarhei.siamashka
Sat Oct 7 16:07:12 CEST 2006

On Saturday 07 October 2006 16:51, Michael Niedermayer wrote:

> > > > And I have difficulties with figuring this shift out. I'll try to
> > > > make an automatic shift detection patch for tiny_psnr.c to solve this
> > > > problem.
> > >
> > > You can use Octave and it's xcorr function to figure out the shift.
> >
> > Well, don't know what this Octave thing is (links are always welcome),
> > but a simple patch for automatic shift autodetection is attached. It
> > works only for shifts +-16384 and is quite slow, but probably could be
> > useful nevertheless. At least I use it in my mp3 decoding quality
> > experiments now :)
> does the shift detection have an anything in common with tiny_psnr.c?
> if no it should either br changes to reuse the comparission code or
> be a seperate tool (detect_shift.c or so maybe)

It is a patch for tiny_psnr.c, if you specify '?' instead of a number for
shift value in a command line, it tries to autodetect shift.

I'm trying to setup a large test using it (a directory with lots of wav files,
each one gets compressed with different bitrates and gets decoded with
different decoders, with results compared against each other using 
tiny_psnr). In such automated test, shift autodetection is very desirable.

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