[Openpvr-devel] filter chains, etc.

[Dave C. <de...@co...>]

I've spent the last week or so tied up in work and over on the Dark Side 
running Windows on my PC rather than Linux (I dual boot), and I've seen 
a lot of PVR-like things from the Windows perspective now (check out 
mediabox.org if you haven't already) and as a result I had some comments 
to see if anyone else is thinking about this too.

For example, a lot of the Windows video-related stuff I see seems to 
imply a workflow like this:

1) Capture video to lossless-compressed AVI (e.g. huffYVUY)
2) Run the stored video through a gamut of filters
3) Compress to MPEG1, MPEG2, DivX, etc. depending on desired purpose

The theory seems to be that you filter out noise, crop the overscan 
area, deinterlace, change frame size, or whatever before trying to MPEG 
compress because this will help improve the visual quality and also 
increase the compression's effectiveness.  The choice of MPEG1, 2, etc. 
then depends on whether you want to burn the result on VideoCD (MPEG1), 
SuperVCD (MPEG2), etc. or if you're storing it to watch later (DivX). 
(One caveat that I should mention is that a large percentage of the 
video-related sites for Windows that I've seen seem to be focusing on 
ripping DVDs to convert to [x](S)VCD, but the same method seems to be 
used for live captures too.)

For some reason I haven't seen this focus on the Linux side (or maybe 
I'm just missing it), where everyone trying to make PVR-like devices 
appears to be just realtime-lossy-compressing the video stream (or in 
the case of DVB, just storing the incoming MPEG2 stream), and later 
playing back that same file.

So my question for everyone else is: does a PVR need filtering?  Does it 
make sense to record in one format and then filter and re-encode to 
another at a later time?  Filtering and re-encoding is likely to be time 
consuming, but if we ever hope to move stored shows to some VCD-variant, 
we have no choice but to do this, right? (unless you're going to record 
in 352x240 29.97 frame/sec (NTSC) 1150 kbit/sec CBR MPEG1 and forsake 
any chance of xVCD or SVCD).

- Dave