Commit Graph

4 Commits

Author SHA1 Message Date
James Zern
1711cf2dbb add vp8 variance test
Change-Id: I4e94ee2c4e2360d6a11a454c323f2899c1bb6f72
2013-02-22 16:25:14 -08:00
John Koleszar
fcccbcbb39 Add vp9_ prefix to all vp9 files
Support for gyp which doesn't support multiple objects in the same
static library having the same basename.

Change-Id: Ib947eefbaf68f8b177a796d23f875ccdfa6bc9dc
2012-11-27 14:12:30 -08:00
John Koleszar
a9c7597adc support building vp8 and vp9 into a single lib
Change-Id: Ib8f8a66c9fd31e508cdc9caa662192f38433aa3d
2012-11-15 10:46:17 -08:00
James Zern
984734436d Fix variance (signed integer) overflow
In the variance calculations the difference is summed and later squared.
When the sum exceeds sqrt(2^31) the value is treated as a negative when
it is shifted which gives incorrect results.

To fix this we force the multiplication to be unsigned.

The alternative fix is to shift sum down by 4 before multiplying.
However that will reduce precision.

For 16x16 blocks the maximum sum is 65280 and sqrt(2^31) is 46340 (and
change).

This change is based on:
1698234 Missed some variance casts
fea3556 Fix variance overflow

Change-Id: I2c61856cca9db54b9b81de83b4505ea81a050a0f
2012-11-06 23:06:44 -08:00