Removed unnecessary comment as requested by Ronald S. Bultje. some more thoughts about the patch:
This is my deduction from what I could find - There was a hard limit of 16 threads in libvpx as there was no benefit to adding more threads based upon the parallelism available in the the codec. This was based upon resolutions upto 3840x2160 (more details below). For 4k/8K videos this restriction does not allow enough parallelism to be exploited. Adding more threads improves performance for higher resolution videos. Details: Tiling and Threading Recommendations Tiling splits the video frame into multiple columns, which slightly reduces quality but speeds up encoding performance. Tiles must be at least 256 pixels wide, so there is a limit to how many tiles can be used. Depending upon the number of tiles and the resolution of the output frame, more CPU threads may be useful. There is limited value to multiple threads when the output frame size is very small. The following settings are recommended for tiling and threading at various resolutions. The number of threads is doubled as there is an option row-mt when set allows row-based multithreading within the tiles. Frame Size | Number of tile-columns | Number of threads 320x240 | 1 (-tile-columns 0) | 2 640x360 | 2 (-tile-columns 1) | 4 640x480 | 2 (-tile-columns 1) | 4 1280x720 | 4 (-tile-columns 2) | 8 1920x1080 | 4 (-tile-columns 2) | 8 2560x1440 | 8 (-tile-columns 3) | 16 3840x2160 | 8 (-tile-columns 3) | 16 In ffmpeg, the number of tiles is controlled with the -tile-columns parameter and the number of threads by -threads. For example, a 640x480 encode would use the command-line -tile-columns 2 -threads 4. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
