[mythtv-users] Plextor external USB capture device

[Brian Wood]

On Mar 27, 2006, at 9:21 PM, Nick Rout wrote:

> My understanding of the driver for the plextor usb units is that it  
> does
> not mux the sound in with the video, this being left to the user's
> software to acheive. The sound is delivered as uncompressed PCM.  
> This is
> in contrast to the Hauppauge PVR 150/250/350/500  cards where the  
> output
> is muxed video/audio, albeit only mpeg2, not mpeg4.
>
> This seems to imply two possible difficulties:
>
> 1. that there could be audio synching problems, depending on how good
> the muxing is done in software; and
>
> 2. some of the performance gain in the hardware mpeg will be lost  
> by the
> need to compress [1] and mux the audio on the cpu,
>
> Seems to me that unless you have a pressing need for USB, or hardware
> encoded mpeg-4, then the PVR cards are a tried and tested formula.
>
>
> [1] assuming you don't want the full uncompressed audio.
>

You are quite correct. The chip in the Plextor was originally  
developed for security systems which did not need audio.

Myth can compress the raw audio to MP3 quite well though, and  
assuming you have a reasonably fast CPU shouldn't be a problem,  
certainly the CPU load is nowhere near what would be required to do  
mpeg-4 in software.