ffmpeg -i h265.mp4 -c:v libvpx-vp9 -row-mt 1 -threads 48 -cpu-used X -deadline good -crf X -b:v 0 outputXYZ. row-mt 1 and -threads 48 stayed consistent through the whole testing process. The basis of the testing commands for this part is below, obviously the -cpu-used and -crf values changed throughout. This file comes in MKV format but was copied (-c copy) to MP4 for the testing. At 4k resolution (3840×2160) 29.97 fps, 30 seconds long, 250Mbps bitrate and file size of 914MB. For MP4 containers, the video codec used is H.264 and the audio codec is AAC, which enjoys near-universal browser support. The input media is from with the H.265 testing file here. To explicitly specify the container format, use the -f command-line option: -f mp4 or -f webm.
The operating system was Ubuntu 18.04 and the FFMpeg version was 3.4.8-0ubuntu0.2. Thanks to exception0x876 at wishosting for the opportunity to use this. The server used for testing had dual Intel Xeon E5-2687W v4 CPU’s set 3.50GHz, meaning 24 cores and 48 threads in total. Download the source code or a build, then install FFmpeg on your device. The testing is using the constant quality option (crf) and the differences with different deadlines along with the cpu used parameter, these effect speed and the outcome quality. See the steps below for converting MP4 to WebM using FFmpeg. To see the encoding options for VP9 WebM with FFmpeg see my post here. Part 3 was h264 with -deadline good compared to -deadline realtime. In this part 4 see FFmpeg encoding speed, fps, size and bitrate for an h265 (hevc) MP4 video file to VP9 WebM using -deadline good with -crf values 15-30 and -cpu-used 0-5.
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