[mythtv-users] software encoding to MPEG2

[Rod Smith]

On Monday 24 September 2007 15:58:17 Tom Metro wrote:
> I'm thinking of installing an analog capture card that has no hardware
> encoder (Philips SAA7130 tuner) to capture shows on the rare occasion
> when both tuners on my PVR500 are occupied. I'd like to be able to
> encode the videos as MPEG2, so they'd be directly compatible with the
> native playback capabilities of the MediaMVP I'm using as a front-end.

AFAIK, this isn't possible in MythTV; you'll have to use mencoder, ffmpeg, or 
some other tool to re-encode the videos to MPEG-2 format. You should be able 
to create a post-recording script to do this automatically, but I've never 
looked into this.

> If I do have to resort to recoding in something other than MPEG2 first,
> and transcoding later, I'm guessing RTjpeg is probably the better pick
> of the two due to it probably being less CPU intensive?

That depends on your system's capabilities and your priorities. In my 
experience, RTJpeg is indeed less CPU-intensive than MPEG-4, but it also 
produces worse video artifacts than MPEG-4. My recollection from when I did 
some experimentation with both formats was that the RTJpeg artifacts were 
particularly bothersome in large dark areas (night scenes, space backgrounds, 
etc.). If you're running a system with a weak CPU, you might prefer putting 
up with these artifacts to risking problems related to running out of CPU 
power; however, if your CPU can keep up with the load of encoding MPEG-4, I'd 
suggest using that format.

If your CPU is weak, you might consider buying a second-hand hardware encoding 
card rather than a software encoding card. You can find some bargains on 
eBay, particularly for non-Hauppauge products. For instance, I picked up an 
AVerMedia M150-D for something ridiculous, like $5 (I don't recall the 
precise price, though). It took some futzing to set up, but it's now working 
reasonably well -- see the wiki entry for the device, which I created 
(http://www.mythtv.org/wiki/index.php/AVerMedia_M150-D).

-- 
Rod Smith
http://www.rodsbooks.com