On Wed, 21 Jan 2004, [ISO-8859-1] Thomas Börkel wrote:
> In the mjpegtools HowTo, I read that a quality factor below 4 is not
> recommended (= not necessary?). Is this still true?
Yes, it's still true - but it is a guide/hint and not a firm rule
or prohibition. The risk is, with most sources, that the average
bitrate will be pushed up to the maximum and not leave any room
for scenes that require a higher rate (at which time the encoder
has to lower the quality).
> A lower -q (2 or 3) gets me higher file sizes, so shouldn't it also be
> potentially better quality?
Yes, it will give better quality. That may or may not be visible :)
> I want to encode about 43 minutes of video with 720x480 final size (4:3
> letterboxed) so that I have a resulting file size (video only) of about
> 950 MB (average of 3000 KBit).
Ah, it's letterboxed so you have large areas of solid black (60 lines
above and below the 360 active lines). That explains the low average
bitrate.
> I tried -f 8 -q 4 -b 4000 -K tmpgenc -D 10 and got 710 MB file size. Any
Well, '-K tmpgenc' lowers the average bitrate so that explains why
the file is smaller than the first encoding (which came out to 950MB).
> recommendations? Is it logical to reduce -q further until I get to my
> wanted file size, if -b can be kept 25% above the average?
Normally folks are interested in lowering the bitrate so that the
files are smaller ;)
If you really want to make larger files then try something like
this:
mpeg2enc -f 8 -q 4 -K hi-res -D 10 -E -8 -2 1
If the file is still too small then try '-q 3' and see what happens.
You may want to add '-b 8500' to allow a higher bitrate than the
default 7500 .
Cheers,
Steven Schultz
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