[mythtv-users] PVR-250 transcode settings

[Stephen Tait]

At 12:52 25/05/2004 +0200, you wrote:
>Hi,
>
>First - let me just tell you my knowledge of video encoding is very 
>limited. With that said, I have a couple of questions:
>
>I have a PVR-250 recording at 6000 kbps (max 7500) and a resolution of 
>720x576 (PAL).
>
>Let's say I want to transcode this to a less space hungry format. Would 
>MPEG4 at 2500 kbps and 640x480 resolution be an acceptable format?

Yes, it's pretty much what I use - just make sure that they're both the 
same aspect ratio - 720x576 is not the same aspect ratio as 640x480. If you 
do resize, it's in your best interest to do a very high quality rescale 
(i.e. bicubic of some variety) or use the scaling function in mencoder - 
Myth transcode may do this already, I'm not sure. Some MPEG4 codecs (yes, 
you DivX!) are pissy about the res, but I've never had problems using XviD 
MPEG4 with resolutions that aren't integer multiples of 32.

>(As I understand it, having a high quality source is important, thus the 
>6000 kbps recording profile on my PVR-250.)

Indeed - the only bugbear I have at the moment is that I get rubbish 
reception on some channels from my piss-poor mini-aerial, so getting high 
quality video is impossible for me.


>Also as I understand it, the signal from the PVR 250 is interlaced. It is 
>deinterlaced when I watch live-TV using the filters I have set up 
>(kerneldeint,denoise3d). But when I record, is it still interlaced and 
>unfiltered video being stored in the resulting file (prior to transcoding) 
>or are my filters applied?

Well, I've not done much tinkering with my recording profiles, but i have a 
similar setup to yours - live/recorded TV is played back through a 
deinterlace filter, since the stream is still interlaced since that's how 
it's recorded (deinterlacing the stream would mean recompressing the stream 
I imagine) - hence whenever the MPEG2's are shoved through mencoder or 
VDubMod, I always apply a deinterlace filter.


>Should I enable the two checkboxes dealing with interlaced MPEG4 
>compression in my transcoder profile? I guess so if the PVR-250 stream is 
>saved without filtering, but not if the filters are applied.

I've not used Myth's inbuilt transcoders (I have another much faster box 
that handles that) so can't really comment on this.


>Anyone care to enlighten me?

Hope it helped!