[mythtv-users] Suggested bitrate for transcoding HD Mpeg 2 to Mpeg 4
belcampo at zonnet.nl
Sun May 29 21:41:07 UTC 2011
On 05/29/11 23:22, Richard Morton wrote:
> I am not sure what you are asking... MPEG4 is commonly referred to but
> is in fact a suite of codecs including at least 2 video codecs an
> audio codec and a container format.
> If you are talking about MPEG4 part 10; otherwise known as H.264 then
> it is much preferable to allow the codec to try and determine what
> bitrate should be used based on a quality variant that you specify;
> somewhere between 16 and 20 is typical.
I would suggest to take some 1 minute test-runs with quality settings
between 16 - 25 and see where YOUR sweet-spot of quality vs space vs
encoding-time and file-size lies.
After 10 runs, which will take less then 30 minutes, you'll be able to
make a meaningfull decision.
> If you are referring to MPEG4 part 2; a.k.a. DIVX/XVID then I dont use
> this codec.
> I tend to use an mkv container rather than the mpeg4 container and
> pass the audio through as broadcast may contain multiple streams and
> is already compressed to hell with MP2 or MP3 so, transcoding it isn't
> a great idea although there may be some small incremental gains
> transcoding to MPEG4 AAC (advanced audio codec, a.k.a mp4a/m4a) as
> long as you dont mind the reduced quality.
> Now my comments about transcoding audio is also true of video,
> although on small screens (30" maybe even 40") any change is likely to
> not be noticeable and the gains of going from mpeg2 to mpeg4part10 is
> very large in disk space (typically half the disk space on 1gb/hour
> with mpeg2) but going from mp3 to m4a is only going to save an
> additional 100mb; although the codeing time for audio is substantially
> quicker of course.
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