[FFmpeg-devel] [PATCH] swscale: Check whether slice height is multiple of chroma subsample.

[Ramiro Polla]

On Tue, Feb 23, 2010 at 9:07 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Tue, Feb 23, 2010 at 12:20:37AM -0300, Ramiro Polla wrote:
>> Hi,
>>
>> Check whether slice height is multiple of chroma subsample.
>>
>> Currently if we take a 410p image and rescale with sliceH = 1, the
>> output is black&white. I did this using the test tool at [1] (renamed
>> to swscale-test2) and the command:
>> ./swscale-test2 -i input.bmp -sws_flags bicubic -pix_fmt yuv410p -s
>> 320x320 -scale -sliceH 1 -pix_fmt bgr24 -scale -o output.bmp
>>
>> I found it weird that this code in utils.c expects the slices to start
>> on subsample boundaries (by shifting nextSlice back and forth), but
>> sws_scale() doesn't:
>> ? ? // calculate buffer sizes so that they won't run out while
>> handling these damn slices
>> ? ? c->vLumBufSize= c->vLumFilterSize;
>> ? ? c->vChrBufSize= c->vChrFilterSize;
>> ? ? for (i=0; i<dstH; i++) {
>> ? ? ? ? int chrI= i*c->chrDstH / dstH;
>> ? ? ? ? int nextSlice= FFMAX(c->vLumFilterPos[i ? ] + c->vLumFilterSize - 1,
>> ? ? ? ? ? ? ? ? ? ? ? ? ? ?((c->vChrFilterPos[chrI] +
>> c->vChrFilterSize - 1)<<c->chrSrcVSubSample));
>>
>> ? ? ? ? nextSlice>>= c->chrSrcVSubSample;
>> ? ? ? ? nextSlice<<= c->chrSrcVSubSample;
>> ? ? ? ? if (c->vLumFilterPos[i ? ] + c->vLumBufSize < nextSlice)
>> ? ? ? ? ? ? c->vLumBufSize= nextSlice - c->vLumFilterPos[i];
>> ? ? ? ? if (c->vChrFilterPos[chrI] + c->vChrBufSize <
>> (nextSlice>>c->chrSrcVSubSample))
>> ? ? ? ? ? ? c->vChrBufSize= (nextSlice>>c->chrSrcVSubSample) -
>> c->vChrFilterPos[chrI];
>> ? ? }
>>
>> Ramiro Polla
>> [1] http://article.gmane.org/gmane.comp.video.ffmpeg.devel/102702
>
>> ?swscale.c | ? ?5 +++++
>> ?1 file changed, 5 insertions(+)
>> cd845850f322996173e636f2655b7b4d5880feb4 ?0004-Check-whether-slice-height-is-multiple-of-chroma-sub.patch
>> From 7b2354c9cf66eaf8d51b527239bc1403354b999c Mon Sep 17 00:00:00 2001
>> From: Ramiro Polla <ramiro.polla at gmail.com>
>> Date: Tue, 23 Feb 2010 00:12:51 -0300
>> Subject: [PATCH] Check whether slice height is multiple of chroma subsample.
>
> problem is that swscale can return such chroma != luma slices and
> chaining slices scalers should work

Sorry, I don't understand what you mean by swscale returning chroma !=
luma slices. Does this mean swscale should support any combination of
chaining slices, even if it's sliceH = 1?