With ffmpeg, itd look like this: ffmpeg -i input.mp4 -c:v libx264 -crf 23 output.mp4. Stream #0.0: Video: rawvideo, bgra, 1366x768, 503562 kb/s, 15 tbr, 1000k tbn, 15 tbcįailed to set value 'ultrafast' for option 'preset:v'Īnother try: ~/Desktop » ffmpeg -f x11grab -r 15 -s 1366x768 -i :0.0 -sameq -vcodec libx264 -preset ultrafast test.mkvĭuration: N/A, start: 1357648985. The default for x264 is 23, so you can use this as a starting point.

Estimating duration from bitrate, this may be inaccurateĭuration: N/A, start: 1357648973.267658, bitrate: 503562 kb/s Values of 6 will result in about half or twice the original bitrate.

And, as I’ve stated before, setting the bitrate with the obvious encoder API has no effect. 18 (or 24 for x265) should be visually transparent anything lower will probably just waste file size. According to ffmpeg command-line documentation, I should be able to explicitly set the bitrate with the equivalent to the -b option or similar, but I’m not able to find this in the AVOptions structure in libx264.c. 23 is a good default for x264, and 28 is the default for x265. This program is only provided for compatibility and will be removed in a future release. In H.264 and H.265, CRF ranges from 0 to 51 (like the QP). Trying to capture screen to video file encoded with lossless x264: ~/Desktop » ffmpeg -f x11grab -r 15 -s 1366x768 -i :0.0 -sameq -vcodec libx264 -preset:v ultrafast test.mkvįfmpeg version 0.8.4-6:0.8.4-0ubuntu0.12.10.1, Copyright (c) 2000-2012 the Libav developers x264-devel Problem with ffmpeg + x264 crf encoding Georg Lippold georg.lippold at gmx.de Tue Aug 25 00:18:06 CEST 2009. Where I can find CRF algorithm implemented in x264 I want to study the default rate-distortion algorithm in ffmpeg and x264.

X264 ffmpeg crf 25