0
When doing 2 pass video encoding with VP8 (libvpx), is there a way to figure out the optimal bitrate, so I don't have to guess?
Something like a small compression test, or some ffmpeg command, that will help me determine the appropriate bitrate?
I tried reading the VP8 1st pass stats file in notepad, but it's all garbled.
I'm using Windows 7 with the latest FFmpeg build.
ClearSky
Posted 2015-09-15T18:38:22.900
Reputation: 39
3
Why not use a constant quality rate control (CRF) that will let the encoder choose an optimal bitrate ?
ffmpeg -i input.mp4 -c:v libvpx -crf 10 -b:v 20M -c:a libvorbis output.webm
The CRF value can be set within [4 ; 63], 4 being the best quality. 10 is a well accepted value. The specified -b:v 20M becomes the maximum allowed bitrate.
Two-pass encoding should only be used when you need a fixed-size file, otherwise, CRF is the preferred method.
More information in the VP8/FFmpeg article.
Ely
Posted 2015-09-15T18:38:22.900
Reputation: 1 378
This CRF value seems low, but maybe the ranges are specific to an encoder? – Tobu – 2015-09-15T23:00:20.923
It's CRF specific to the VP8 encoder which is different from x264's CRF. – Ely – 2015-09-16T11:45:53.910