On Wed, 22 Sep 2004, James Bigler wrote:
> 2. I don't like popping. I've noticed that depending on various
> parameters I've chosen for mpeg2enc I get intermittent popping.
"popping" is not a term usually associated with video. When I have
heard the word "popping" used it's been in the context of audio as
in "clicks and pops" or "chirps and popping". And sometimes the
audible pops/clicks/chirps are due to the _de_coding software and/or
sound drivers (MPlayer comes to mind - depending on the version of
gcc used to compile MPlayer's MP2 audio decoder you'll hear artifacts).
What exactly do you mean by "popping"? Or are you in that case
thinking of 'mp2enc', the audio MPEG-1/Layer-II audio compression
program?
> -g 1 -G 1
>
> This doesn't really seem to help. I've found that -g 1 -G 3 does much
> better, while -g 1 -G 2 causes severe popping.
That sounds like a bug in an earlier version - but I have no idea
what is meant by 'popping' in "video".
My initial guess is that you're either using an older version of
the tools (or there's a bug in the cvs version that needs attending
to) _OR_ you're on a IA32 system and have specified "-q" of 3 or less.
If there's not a lot of (fast) motion then I wouldn't expect to
see any difference between regular and very short GOP sizes.
> I've read in the archive that -H can help with images that are pretty
> free of noise, but I don't notice much of a difference.
Differences might be more apparent when the viewing area is larger -
full screen mode.
> I've also tried to crank up the bit rate, but that can result in poor
> quality images once the bit rate gets too high. Is there some intuition
> I'm missing?
That doesn't feel right at all. Past a certain point no more bits
are needed to encode the data - i.e. you can specify 6 megabits/sec
but if only 3 are needed then increasing the bitrate will not
improve the image but it won't degrade the image either.
Possible I suppose that the playback software can't deal with high
rate video.
> So if I don't care about file size, and I want the best quality movie
> what kind of parameters should I be using?
You are using the necessary options for VBR (Variable Bit Rate) I
hope - by default I think the encoder uses CBR (Constant Bit Rate)
for its MPEG-1 encoding. That might make a difference - more bits
where they're needed type of thing.
MPEG-2 is just as portable as MPEG-1 - I haven't seen a software
player yet that could only handle MPEG-1. Does 'popping' (whatever
that is;)) happen if you use MPEG-2? If not then that narrows somewhat
the areas to look for the problem(s).
Without knowing what 'video popping' is there's not much more I can
add.
Cheers,
Steven Schultz
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