[mythtv-users] Transcoding overhead, could use some advice...

[Curtis Wood]

   Thanks, the lockups are simply because the load gets way to high -
the last time I was recording like 3 movies over night I came in the
morning and the load was like at 8.50! I am in the market for a 250pvr,
and Im assuming from your comments - it would be well worth the
purchase?
    This thing is till transcoding the movie - I had the audio pushed
down to '3' - would that be what is causing this thing to still be
churning 10hrs later? Other than that - it is set to mpeg/8000 bit rate,
hq and the mvr or something...
   I think I will stop using the encoding feature...

Tahnks again,
Curtis

On Sun, 2003-12-14 at 14:23, James L. Paul wrote:
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> On Sunday 14 December 2003 09:54, Curtis Wood wrote:
> >    Is there anyway to speed up the process of transcoding, currently it
> > is taking hours to transcode. a 2hr movie transcoded to the highest
> > format is taking from 4-6+ hours to finish. Im running the backend and
> > frontend  on the same machine, while it is transcoding I can't record -
> > let alone transcode another recording (other wise the frontent locks
> > up)... I realize that this may be a CPU intensive task (which it is,
> > jumps the load up to 3.0-5.0) - but it doesnt seem to make a difference
> > (in time) whether anything else is running or not, as in watching live
> > tv...
> 
> The transcoding is indeed CPU-bound. The compression ratio affects transcoding 
> time somewhat, but in general you aren't going to dramatically reduce your 
> transcoding time without a lot more CPU. Your processor is crunching as fast 
> as it can, end of story. You can only make it faster by asking it to do less, 
> and that involves significant tradeoffs when if comes to compressing video in 
> software on a general purpose CPU.
> 
> What I'd love to see is a way to use hardware encoders like the PVR-250 for 
> transcoding, and even then we would have the overhead of software decoding to 
> feed the encoder for transcoding. Ahh well. :)
> 
> I don't do a lot of transcoding with mythtranscode, but I assume there's a bug 
> that prevents you from transcoding in the background while recording. There's 
> no inherent reason I'm aware of that should cause this problem. The 
> transcoding threads should be the lowest priority, so sorry to hear you are 
> having lockups. Perhaps fixing that problem will make living with transcoding 
> easier.
> 
> Myself, I chose to avoid transcoding as much as possible. The PVR-250 cards 
> really take burden off the CPU and I can avoid encoding by recording directly 
> to a format that is very versatile. I know that may not apply to your 
> situation, but the cost of the cards was way lower for me than the cost of my 
> time in working around the issues of not having hardware encoding. :)
> 
> My advice: try to reduce your need to transcode for common use. If that's not 
> an option, add more or faster CPU. At the very least try to solve your lockup 
> issue so that transcoding does not interfere with normal recording. And good 
> luck!
> 
> >    Im running everything on a P4 2.4 ghz, 256mg ram (could be an issue),
> > all on top of GenToo... Im still on 0.12, waiting for the transcoding to
> > finish so I can compile 0.13 - its been processing since 7:30 this
> > morning (roughly 7hrs)...
> >
> > TIA,
> > Curtis
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