Ticket #200 (new enhancement)

Opened 1 year ago

Better x86 IDCTs for ffmpeg

Reported by: astrange Assigned to:
Priority: normal Milestone: Sometime after 1.0
Component: ffmpeg Version:
Severity: normal Keywords:
Cc:

Description

The IDCT is the slowest part of mpeg2/4 decode. ffmpeg has very good ones, but the best are GPL'd and therefore disabled for us. Plus they were only ever MMXEXT anyway.

We might be able to speed it up by writing some using SSE. Trouble is, IDCTs are really hard; it might be best to try converting the altivec code?

http://en.wikipedia.org/wiki/IDCT

http://web.archive.org/web/20060113150501/http://skal.planet-d.net/coding/dct.html

(Skal's is better than any of the current ones but he doesn't really explain any of the IDCT part)