[XviD-devel] Variable Quant + Variable Bitrate (Can it happen?)
Lee Morgan
leeamorgan at comcast.net
Sat Jan 29 04:25:31 CET 2005
Would someone please take a bit of time to explain to me why there
can't be a variable quant with variable bitrate mode?
I know, I know - it exists (2 pass right). But that's not what I mean.
To my understanding 2 pass takes the input bitrate as a avg it intends
to meet. It then analyzes the video determining what parts of the video
need what bitrate then on the second pass varies the quantizers as need
to achieve that overall bitrate (more or less correct?).
It's been stated that 2 pass has a method of determining what level of
quantization a macro block should have (to retain high quality).
Could this not be determined "on the fly" during a single pass encode
to allow instead of a fixed quant but rather a variable quant +
variable bitrate mode? Which would use the lowest needed quantization
for a macro block while still allowing for higher ones to be used when
possible.
This way it is possible to have a high quality single pass fixed quant
2 without wasting bits.
Thanks for your time in advance,
Lee
P.S. Sorry if this double posts (I've been having problems with my mail
today - and I didn't see it come through on the list).
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