[FFmpeg-devel] SWSCALE: Colorspace conversion for images

[Frank Barchard]

On Tue, Mar 29, 2011 at 2:40 PM, Michael Niedermayer <michaelni at gmx.at>wrote:

> On Tue, Mar 29, 2011 at 01:58:57PM -0700, Frank Barchard wrote:
> > Bump swscaler width limitation from 5120 to 16384.
> >
> > Advantage: images (ie jpeg) are often larger than 5120 these days.
> >  5120x2880 is about 15 megapixels
> >
> > Disadvantage: slightly slower
> >
> > no scaling
> > timex ffmpeg -y -i tulip2.mp4 tulip2.yuv
> > timex 8866.21ms
> >
> > scaling
> > C:\ffwork>timex ffmpeg -y -i tulip2.mp4 -s 1272x724 tulip2.yuv
> > timex 23633.13ms with VOFW 5120
> > timex 26246.90ms with VOFW 16384
>
> uhm
> could you try 21504 instead of 16384 ?
>

21504 works better.  Heres a benchmark

VOFW 5120  VOFW 21504    Note10438.8    10344.2       timex ffmpeg -y
-i tulip2.mp4 tulip2.yuv25611.9    24256.9       timex ffmpeg -y -i
tulip2.mp4 -s 1272x724 tulip2.yuv24485.7    26006.6       "28573.1
24291.3       "24069.1    26995.9       "25684.95   25387.675
average

This is on a Nehalem i7.  Despite being a 500 frame, 720p video, the numbers
fluctuate, so I took an average of 4 runs.

Another reason I'd like this change is youtube accepts videos with higher
resolutions than 5120.
16384 is vp8's maximum resolution, so that should keep us amused for a
little longer.
I thought 16k would fix into L1 better, but I guess it had collisions.

diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h
index daa6731..fc684f1 100644
--- a/libswscale/swscale_internal.h
+++ b/libswscale/swscale_internal.h
@@ -34,7 +34,7 @@
 #define MAX_FILTER_SIZE 256

 #if ARCH_X86
-#define VOFW 5120
+#define VOFW 21502
 #else
 #define VOFW 2048 // faster on PPC and not tested on others
 #endif