[mythtv-users] bitrate questions

[Maarten]

On Tuesday 17 August 2004 00:34, Chris Petersen wrote:
> > But on the other hand, SVCDs are 480x480 res, always mpeg2, look
> > about the same (or even just slightly better) as my mythtv recordings
> > but they manage to squeeze 80-100 minutes on a 800 MB CD.
>
> Actually, svcd looks like crap if you put more than 60 minutes onto an
> 800M disk.  SVCD video bitrates at 1500kbps (with audio at 160), which
> is about 65 minutes per 795 megs (to leave 5M of space for svcd file
> system stuff), are about as low as you can go and still maintain a
> decent amount of quality.

I seem to have some close-to-two-hour movies on one single SVCD which look 
okay (if not surprisingly good), but yeah, in general I would agree with you 
on the 60-70 minute cap for SVCD media...   some movies differ in this 
respect, but not many. 

> However, this really doesn't answer the quality difference issue.  I
> have plenty of 720x480 avi files (presumably mpeg4/xvid/divx) that are
> fractions of the size of my 640x480 nuv files (say, 350M for 40 minutes
> of commercial-free show, compared to 2-3G for mine) with WAY better
> quality, no noticeable artifacts, etc.

You use 2G+ per 40 minutes?  wow...  but that doesn't exactly correlate to 
your 2800Kbps setting, does it?

> Granted, my nuv files (recorded around 2800kbps) have high-quality mp3
> audio, but it shouldn't account for the gigabytes of difference in file
> size.  My nuv files also look pretty decent, but I've set the "max"
> mpeg4 quality to 1, and the "min" to 2.  (bumping up the "min" setting
> was by far the best thing I did to improve the image quality)

I'll try that to see the difference.

> Perhaps it relates to 3:2 pulldown?  Is this too processor-intensive for
> myth to do realtime?  I'd happily take a disk-hit to start (say, 10-20G
> per hour) to have it later compress down with 3:2 pulldown, deinterlace,
> etc., to something around 500M/hour without commercials.

Well, except for those holidays...  recording with such a profile the disk 
would fill up in just days.  But apart from that, yeah, that would certainly 
be nice... :-)

I don't know what 3:2 pulldown is.  Is that the same or similar to two-pass 
encoding ?  Is this what prevents realtime encoding to make these smaller 
files ? 

> -Chris

thanks,
Maarten

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