[mythtv-users] bitrate questions
Maarten
mythtv at ultratux.org
Mon Aug 16 17:45:58 EDT 2004
Something has me stumped for a while now. I just have to ask...
(Note: I'm not complaining about anything, just curious...)
I've been running mythtv for 6 - 8 months now, and I use 480x480 res @ bitrate
3000, which gives me reasonable quality (my feed isn't too good to begin with
and I have a fairly crappy bttv 8x8 card, not a PVRx50 or similar).
I started at default settings (bitrate 2200) but that gave me more artifacts
than I liked, so I slowly upped that to 3000.
This setting means mythtv takes a little more than 1 Gig per hour.
Now to what I don't understand. Supposedly, the mpeg4 encoder which I use
gives somewhat smaller files than what an mpeg2 stream coming from a PVRx50
would give, right ? 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.
So, taking the (supposedly) more optimized mpeg4 encoding into account as
well, where does this discrepancy in space come from?
Mythtv: 480x480, mpeg4 yields 1.1GB/hour
SVCD 480x480, mpeg2 yields 0,6 GB/hour
Well, obviously the SVCD uses a lower bitrate, but how do they manage to use a
lower bitrate while still getting good quality ? They fit almost twice as
much video in the same space...
TIA,
Maarten
--
Linux: Because rebooting is for adding hardware.
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