Color distortion when video size does not match the virtual screen size (patch suggestion included)

[David Hart]

Videos encoded at a different resolution to the Ren'Py virtual screen size result in color distortion of the video (looks too "green"). For example, playing a video encoded at 1920x1080 with config.screen_width = 1366 and config.screen_height = 768 results in this distortion, but playing the same video with config.screen_width = 1920 and config.screen_height = 1080 does not.

This issue appears to be caused by the flags supplied to libswscale. The file module/ffdecode.c enables a "fast bilinear" scaling algorithm which appears to cause the color distortion. Switching to a different scaling method (e.g. bicubic filtering) appears to fix the issue. A suggested fix is therefore to change the line:

static int sws_flags = 1;

to:

static int sws_flags = SWS_BICUBIC;

Issue observed on Ren'Py 6.12.2, 6.13.12 and 6.14.0 for Linux and Windows. Fix tested on 6.13.12 for Linux only.

[Tom Rothamel (renpytom)]

I've made this change, although I chose to use SWS_BILINEAR instead of SWS_BICUBIC, for speed reasons.

[David Hart (davey3000)]

Thanks, I'll test the change in the next 6.14.0 build.

For reference, the 6.14.0 build that the issue was still present in was 6.14.0.313.

[David Hart (davey3000)]

Verified that this is issue is fixed in build 6.14.0.329 (tested on Ubuntu 12.04 LTS 32-bit and Windows 7 64-bit).