[FFmpeg-devel] [PATCH] Change default behaviour of scale filter from 'progressive' to 'auto'

[Reimar Döffinger]

On Wed, Apr 04, 2012 at 03:15:08PM +0100, Tim Nicholson wrote:
> 
> 
> 
> 
> ----- Original Message -----
> > From: Baptiste Coudurier <baptiste.coudurier at gmail.com>
> > To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> > Cc: Tim Nicholson <nichot20 at yahoo.com>
> > Sent: Wednesday, 4 April 2012, 2:48
> > Subject: Re: [FFmpeg-devel] [PATCH] Change default behaviour of scale filter from 'progressive' to 'auto'
> > 
> > On 04/03/2012 09:07 AM, Tim Nicholson wrote:
> [....]
> >>  diff --git a/tests/ref/vsynth1/dnxhd_1080i b/tests/ref/vsynth1/dnxhd_1080i
> >>  index f8f6df0..de4732e 100644
> >>  --- a/tests/ref/vsynth1/dnxhd_1080i
> >>  +++ b/tests/ref/vsynth1/dnxhd_1080i
> >>  @@ -1,4 +1,4 @@
> >>   027c985483caab9397592bf27477dce1 *./tests/data/vsynth1/dnxhd-1080i.mov
> >>   3031911 ./tests/data/vsynth1/dnxhd-1080i.mov
> >>  -0c651e840f860592f0d5b66030d9fa32 *./tests/data/dnxhd_1080i.vsynth1.out.yuv
> >>  -stddev:    6.29 PSNR: 32.15 MAXDIFF:   64 bytes:   760320/  7603200
> >>  +3c3226518a0f56468bf56a6682e31fae *./tests/data/dnxhd_1080i.vsynth1.out.yuv
> >>  +stddev:   14.22 PSNR: 25.07 MAXDIFF:  119 bytes:   760320/  7603200
> > 
> > A default change that produces a difference like this is unacceptable IMHO.
> > This is quite a big difference.
> > 
> 
> If this was a real world case would agree. However the fate test deliberately puts progressive material in an interlaced stream, and then back again. If you do the same round trip with interlaced material the results are very different. The results are only worse because the stream is being handled in the format it claims to be, rather than blindly handled progressively.

However that is a rather real-world behaviour for DV and DNxHD files as
far as I can tell.
But regardless of that, I am very much against changing the test
reference, that bad PSNR will make it hard to see actually codec
bugs.
Instead the command for the test case should be changed so that the
scale filter is forced to use progressive scaling.