Non Conformant Bitstream output for input where bframes>6, b-adapt 2 and weightp is enabled
Hi,
I’ve run into a weird issue where x265 will output a consistnatly non conformant bitstream that causes hardware decoders (specifically cuvid) to fail to decode properly when using --bframes >=7 --b-adapt >=1 --weightp on the source video attached (source.264).
Also attached is an example non conformant output stream encoded with --preset veryfast --rc-lookahead 100 --bframes 8 --b-adapt 2 --weightp
No errors are thrown during playback by any decoders I’ve tried: it either displays properly, or it doesn’t, around 8 seconds in.
The specific infringement is,
“The value of delta_chroma_offset_l0[ i ][ j ] shall be in the range of −4 * WpOffsetHalfRangeC to 4 * WpOffsetHalfRangeC − 1, inclusive. (Spec. item: 7.4.7.3)”
(Acccording to Elecard Streameye)
I’ve done some fairly extensive testing and come to the conclusion that this consistantly happens at 8/10 bit with all presets (with rc-lookahead increased from 5 to test ultrafast) with the above settings. Can’t think of why, this isnt really my area of expertise, though maybe I’ll attempt to do some debugging myself over the next few days and if I do find anything I will update here.
Version info for my own machine where this is consistantly reproducable, however I’ve also been able to reproduce this elsewhere
x265 [info]: HEVC encoder version 3.4+27-g5163c32d7
x265 [info]: build info [Windows][GCC 10.2.0][64 bit] 8bit+10bit+12bit
x265 [info]: using cpu capabilities: MMX2 SSE2Fast LZCNT SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2