some h264 videos fail with videotoolbox on certain hardware. the error code returned by ​VTDecompressionSessionCreate is -12913 (kVTVideoDecoderNotAvailableNowErr). it works on my Mid2010 MacBook? Pro but not on my Hackintosh with an i7-6700k. this was first reported in the mpv issue tracker ​here. also tested the same file with VLC on my hackintosh and there the hw accelerated decoding works.
a sample file can be found ​here.
[h264 @ 0x7fb24b001200] no frame!
[h264 @ 0x7fb24883ae00] no frame!
[h264 @ 0x7fb248822600] no frame!