[mythtv-users] Transcoding questions

[Steve Peters - Priority Electronics]

Each has its tradeoffs - mencoder seems to do a MUCH MUCH better job at
making xvid files. But, ffmpeg has way more options. If you're looking to
compress these files down, you'll want to do mencoder with the xvid video
format. It's also nice, cause you can play xvid's on pretty much any OS (ie,
you may have a windows laptop).

Mencoder is much much slower though, but if you're not doing too much
encoding, I think it's worth the tradeoff. To give you an example, I encoded
a few movies to xvid using ffmpeg, then with mencoder, all other settings
being the same, the ffmpeg files were 2.5 to 3GB each...not much savings
over just using myth's built-in transcoding function. When I did the
transcoding using mencoder, the same videos came out to around 500MB to
800MB, and even looked better too.

Give it a run yourself so you can compare the quality. If you're doing
animation, you can use lower quality settings than regular video, and it
will still look good. To give you an idea, here are the xvid settings I use
for movies and the like:

Where would you like to export the files to? [/media/200GB/converted]
Enable Myth cutlist? [Yes]
Enable noise reduction (slower, but better results)? [No]
Enable deinterlacing? [Yes]
Crop broadcast overscan border (0-5%) ? [0]
Audio bitrate? [128]
Variable bitrate video? [Yes]
Multi-pass (slower, but better quality)? [No]
VBR quality/quantisation (1-31)? [8]
Default resolution based on requested dimensions.
Width? [640]
Height? [480]

For episodes of The Simpsons, I change the quantisation setting to 10
(Higher number = lower quality). Mencoder is slow and can not take advantage
of dual core systems (I run a Core 2 Duo), but you can just transcode two
videos at the same time and each runs at full speed. There is a ton of
reading to do on nuvexport and quality settings and the like here:
http://www.mythtv.org/wiki/index.php/Nuvexport.

It took me a lot of testing before coming up with those settings. One last
thought, if you're gonna do test runs, I recommend you do a 3-5 minute clip
instead of a whole episode. That will save you a ton of time.
-Steve



 


-----Original Message-----
From: mythtv-users-bounces at mythtv.org
[mailto:mythtv-users-bounces at mythtv.org] On Behalf Of James Fidell
Sent: Monday, July 23, 2007 1:57 AM
To: Discussion about mythtv
Subject: Re: [mythtv-users] Transcoding questions


Steve Peters - Priority Electronics wrote:
> Dave,
>  
> I'd recommend Nuvexport with the mencoder option (run: nuvexport 
> --mencoder). I currently "transcode" episodes of The Simpsons down to 
> around 150MB each at very great quality. Nuvexport will also get rid 
> of the commercials. Also, since it runs outside of mythtv (for now), 
> but since it reads the mythtv database, you can select the shows you 
> want to transcode, and still have the originals untouched in your 
> mythtv recordings section. nuvexport can transcode to ipod formats 
> (run it without mencoder) as well. Just save the transcodes to your 
> videos folder and play them from there.

The nuvexport source comments suggest that ffmpeg is the better option for
encoding.  Is that no longer the generally accepted view, or does mencoder
just seem to work better for you?

James
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