[FFmpeg-user] How about multi-pass encoding for H264?

[Lou]

On Thu, 8 Aug 2013 10:25:19 +0800
"韩瑞松" <550399108 at qq.com> wrote:

> Now I use 2-pass X264 encoding to transcode videos to flv format.

Are you sure you need to perform more than one pass? Normal bitrate
based two-pass mode is generally used if you are targeting a specific
output file size. Otherwise you can use one pass with -crf. For
examples using both methods see:

https://trac.ffmpeg.org/wiki/x264EncodingGuide

> Someone told me that 4-pass will reduce the size of the output file.

Then wouldn't 8-passes be even better?
 
> Is that true?

Anything over two passes is a waste of time with few exceptions. See:

<http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-x264.html#menc-feat-x264-encoding-options-misc-preferences>

> How can I use 4-pass encoding.

ffmpeg -y -i input -pass 1 … output
ffmpeg -y -i input -pass 2 … output
ffmpeg -y -i input -pass 3 … output
ffmpeg -y -i input -pass 4 … output
…
ffmpeg -y -i input -pass 256 … output