http://en.wikipedia.org/wiki/Purevideo# ... reVideo_HD
E.g. 854x480 and 1024x576 videos can't be played using H/W acceleration on my ION - so I have to turn off it manually.All current third generation PureVideo hardware (G98, MCP77, MCP78, MCP79, MCP7A) cannot decode H.264 for the following horizontal resolutions: 769-784, 849-864, 929-944, 1009–1024, 1793–1808, 1873–1888, 1953–1968 and 2033-2048 pixel