[mythtv-users] MPEG4->MPEG4 transcode? (slightly OT)

[Cory Papenfuss]

> Which has always puzzled me.   Given the advantages of MPEG4 and
> the fact that a software encoder card + fast CPU costs much less
> than a hardware encoder card + slow CPU,  why would one pay for the
> hardware encoder?  I can see where it's a stand-alone front end
> and a noisy CPU fan is an issue, but in general?
>
 	While not intrinsically necessary, software-based cards are 
generally of inferior capture quality.  In particular, bt87[89]-based 
cards do not have a comb filter, which significantly limits luminance 
bandwidth for composite (and by extension, tuner) captures.

 	A 600MHz machine is marginal to play an MPEG2 stream through 
MythTV with any filters or other I/O processing going on.  PVR-150's can 
be had for $60 or so.  Even craptastic bt8xx-based cards are $25ish new. 
I don't think that the argument holds.

 	Oh, and hardware-based card capture systems scale.  It's not too 
tough for a moderate (1GHz) machine to capture 3-4 MPEG2 streams 
simultaneously.  Two software-based cards will saturate a PCI bus and 
require about 1GHz worth of CPU apiece to realtime-compress.... plus the 
600MHz to *play* if you do livetv.

-Cory

-- 

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* Cory Papenfuss                                                        *
* Electrical Engineering candidate Ph.D. graduate student               *
* Virginia Polytechnic Institute and State University                   *
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