[mythtv-users] PVR250 Settings?

[Jeff]

At 11:28 AM 2/12/2004 -0800, you wrote:
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>On Thursday 12 February 2004 08:07, Jeff wrote:
> > Probably because I don't necessarily know what I'm doing. :-)
> > I played around a bit and this seems to be ok.
> >
> > About transcoding though, I'm going from MPEG2 off the PVR250 to
> > MPEG4...at least that what I think I'm doing. As far as the bitrate, I
> > really didn't know what the bitrate does for the transcoding setting so
> > I left it alone. I guessed that since MPEG4 is compressed the bitrate
> > setting doesn't mean much on the output file side so perhaps it might
> > be limiting the sample rate taken from the input file.
> >
> > As I said, I'm guessing at a lot of this.
>
>The bitrate setting means a whole lot. Like Derek said, a file captured at
>1331Kbps is going to be 1331Kbps, regardless of encoding type. The end result
>will be files of the exact same size. An mpeg2 capture at 6000Kbps should
>have about the same visual quality of an mpeg4 at 2000Kbps (ymmv).
>
>To make matters worse (in your case), you're tossing out half your lines of
>resolution in that transcode, so you're only preserving half the resolution
>of the mpeg2 capture, but the same bitrate. Effectively, you're using just as
>much space as the mpeg2 capture for an mpeg4 with half the resolution. This
>is a Very Bad Thing (tm).
>
>I'd recommend capturing your mpeg2 stuff at roughly 3x the bitrate of what 
>you
>want the mpeg4 to be. Capture 4500Kbps mpeg2, then transcode down to your
>1331Kbps mpeg4, or something like that. I find it hard to imagine a 352x480
>1331Kbps mpeg2 results in something that is actually bearable to watch...

Ok, apologies to all.
I just checked and I confused my bttv card with my PVR.

My PVR card is set to capture at 640x480 @ 4000 Kb/sec.
I transcode to MPEG-4 at 352x240 @ 1331 Kb/sec.



> > At 09:20 AM 2/12/2004 -0600, you wrote:
> > >ummm. y?
> > >
> > >a 1331 bitrate file is going to take up the same amount of space no matter
> > >how you encode it.  you're just throwing away cpu cycles transcoding, not
> > >to mention quality.
> > >
> > >Jeff wrote:
> > >>>  On Wed, 11 Feb 2004, Matthew Daubenspeck wrote:
> > >>> > I finally purchased a PVR250 and got it installed. Let the fun begin!
> > >>> >
> > >>> > What are other PVR people using for their bitrate settings? I want to
> > >>> > find a happy middle between space and quality, and would be
> > >>> > interested in finding out what the rest of you think...
> > >>
> > >>I use 352x480 for a resolution and 1331 (not scaled) for a bitrate.
> > >>I transcode these to 352x240 at the same bitrate.
>
>
>- --
>Jarod C. Wilson, RHCE
>
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