[mythtv-users] Changing width resolution for PVR-250/350's

[f-myth-users@media.mit.edu]

    > Date: Tue, 17 Jan 2006 21:27:59 -0400
    > From: Greg Estabrooks <greg at phaze.org>

    > > But I also saw a neglible change in file sizes, too.  Is this 
    > > the expected behavior?

    >  Certainly, bitrate is bitrate regardless of the resolution. 2Megabits at 
    > 480x480 is just as much data as 2Megabits at 720x480.

Oh duh.  Of course; I totally wasn't paying attention to the bitrate
page.  Well, we already knew I was an idiot... :)

				> 			  The difference
    > is how much data per sampled pixel. Often lowering the resolution and 
    > turning up the bitrate can increase picture quality but it also depends
    > on just how clean your source is to start. If you've already got a clean source
    > then you can get away with a lower bitrate.

Does anyone have suggestions for -their- ideas of reasonable bitrates
before I spend a bunch of time experimenting?  I have a clean feed,
and I've been reasonably happy with either "TiVo High" quality, or
"VHS EP mode" quality (yes, I know the latter is substantially fuzzier,
and yes, I'm not even talking SVHS :).  Approximate figures for either
one would make good starting points for my experimentation.  (And if
anyone thinks that some particular width x height should go along with
these bitrates, by all means, share.)

Since there's both a bitrate and a max bitrate (4500 and 6000 in my
current setup, which are the defaults), there are a lot of variables;
are their any I should stay away from?  Is it sensible to lower the
bitrate to, say, 3000 or even lower, and does it make sense to leave
the max bitrate high?  Is this used only during a scene change or
lots of motion/flow?  I'm using a 350 as my TV-out; has anyone noticed
any particular bugs/crashes/artifacts from using other bitrates?

    >  Plus analog cable broadcasts are normally broadcast in a "resolution"
    > of close to 544x480 in most markets. People keep focusing on 720x480
    > as it is the most well known NTSC DVD resolution.

Right.

    > > I didn't restart mythbackend after each set of changes, and I'm not
    > > sure if they take effect instantly or not.)

    >  They would take effect immediately so the next time a recording is started
    > they would use the new profile information.

Good.

    > > mplayer or something, would using 640x480 or some other size make for
    > > a more reasonably-transportable setting?  Any other comments?

    >  What do you mean by transportable in this context? Personally all of
    > my recordings are done at a resolution of 544x480, but of course ymmv.

Basically, if I decide to move these recordings elsewhere and watch
them on a computer, my guess was that the less rescaling has to
happen, the better.  Since the input material is all 4:3 SD NTSC,
my guess is that I should specify a ratio of width to height that's
-also- 4:3, meaning that no pixels need rescaling if I were to just
display this stream in mplayer or something.  Is this likely to
matter?  (That would work out to 640 x 480, of course.)

Thanks!