[mythtv-users] transcoding settings for MPEG4

Tom Metro tmetro+mythtv-users at gmail.com
Sun Apr 22 17:17:05 UTC 2007


Robert Current wrote:
> ...by changing the settings in there for "Maximum Quality" and
> "Minimum Quality" and now all my video looks as crappy as something
> streaming on YouTube!!!
> 
> So, if someone would kindly go to:
> Setup->TV Settings->Recording Profiles->Transcoders->Autodetect from MPEG2
> change from the default use Codec of RTjpeg to MPEG-4, and then
> (without changing anything from the defaults) tell me what the umbers
> are for...

[I'm relying to this in its own thread as I'd like it to get better 
visibility.]

Experimentally arriving at transcoding settings can be a slow process. I 
agree with the poster above that it'd be nice to see what others have 
found works well.

I'd like to create a page in the wiki like:
http://www.mythtv.org/wiki/index.php/Recording_Parameters

except instead of listing recording parameters, it would list 
transcoding settings. Here are the elements I think would be worth tracking:

First the transcoder settings:

Bitrate:
Maximum quality:
Minimum quality:
Max quality difference between frames:

(I'll assume all of these options are unchecked unless specified otherwise.)
Scale bitrate for frame size:
Enable high quality encoding:
Enable interlaced DCT encoding:
Enable 4MV encoding:
Enable interlaced motion estimation:

Optionally also include:
Audio codec: MP3 (I'll assume)
Sampling rate:
MP3 Quality:

Optionally list the "first screen" parameters, such include Custom 
Filtering, Lossless transcoding, and Resize video, if they aren't left 
at their defaults.

Finally, include some benchmarks, such as the size of 2 or 3 files:
File size: ?.? GB for ? minutes at X x Y resolution
File size: ?.? GB for ? minutes at X x Y resolution
File size: ?.? GB for ? minutes at X x Y resolution

and a subjective comment on the quality, along the same lines as what is 
seen in the wiki page above.

Reply on list, or to me personally, and I'll compile the responses in a 
table on the wiki and post the URL in a follow-up.

  -Tom


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