[FFmpeg-devel] [RFC] Rework swscale-test.

[Ramiro Polla]

Hi,

Currently swscale-test runs tests in the following way:

for each possible input format
 convert reference from yuva420p to input format
 for each possible output format
  for a bunch of up/down/un-scaled horizontal and vertical conversions
   for each algorithm
    convert from input format to output format
    run crc on output
    convert from output format back to yuva420p
    run ssd against reference

This spends most of the time to/from yuva420p. It also repeats many
conversions to/from yuva420p, so that when one conversion is wrong,
you get a bunch of lines differing in the output.

I want to know what you guys think of changing it to run something like:

for each possible input format
 convert reference from yuva420p to input format
 for each possible output format !!! starting from current input format
  for a bunch of up/down/un-scaled horizontal and vertical conversions
   for each algorithm
    convert from input format to output format
    run crc on output
    convert from output format back to input format !!!
    run crc again !!!
    run ssd against input !!!

I marked the changes with "!!!". This should still cover all
conversions but dramatically reduce the time spent on swscale-test
(from 2m to about 40s). One thing that changes a lot is how SSD should
be performed. It will no longer be a simple 4 plane yuv SSD, but
rather compare the data in the input pixel format. This is fairly easy
to do in 8bpp and 16bpp formats, but somewhat trickier on formats like
monow, rgb4, rgb555. monow could use a simple xor and count number of
ones (hey, that's still a sum of squared differences =). For the rest
(similar to rgb4 and rgb555) av_read_image_line() could be used, but
then I thought I'd ask here first if this is not a fundamentally
flawed approach. Do the ssd values still have meaning if they're
calculated differently for some types of pixel format? Are they for
some reason less accurate than in yuva420p?

Comments, suggestions for better ways to test swscale, etc...?

Ramiro Polla