Good day everyone
I would like to know using more threads does effect the quality & of course without VBV?
like if I sued this commands
x264 --crf 17 --threads 6
x264 --crf 17 --threads 14
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Last edited by alkoon; 21st Nov 2020 at 22:39.
More threads adversely affects quality and compression ratio, but it's mostly negligible for threads 6 vs 14 at crf 17 .
It's measurable in metrics, and the filesize will be slightly different so you 'd have to so serial tests at 17.x until the bitrates match, but at high CRF , low bitrate ranges high amount of threads can become more important and noticable
VBV also adversely affects quality and compression ratio, and CRF+VBV sometimes has bizarre artifacts, not recommended
CRF+VBV sometimes has bizarre artifacts, not recommended
Cu Selurusers currently on my ignore list: deadrats, Stears555
Thank you for this information
Actually I'm surprised that with more threads I got more bitrate and more size!!
No surprise. More threads means that the frame content is split into smaller pieces, and each thread "sees" less video content to compare with and to find similarities useful to spare size. The result will have more intra blocks it could not find a smaller substitution for.
It is not recommended to use more threads than the encoder heuristic calculates. More threads will only provide a small amount of speed-up due to saturation in the multi-threading management, but the encoding will be less efficient per thread.