On Wed, 31 Jan 2007 19:33:32 +0100, Andrea Giuliano
<[EMAIL PROTECTED]> wrote:
Dear all,
I hope this is not a trivial question!
I'm creating xvid movies from several sources, but i would like to know,
at least approximately, how big the resulting files will be, given the
bitrate, the frame size, and so on.
I usually do two pass encoding, which I guess makes more difficult to
calculate this size, but maybe there is a way.
Any hint will be very appreciated.
Best regards.
Hi Andrea,
ok i'll share some experiment results i obtained making some tests
compressing several movies with divx5 2-pass (i think xvid is quite the
same). I've made these tests many years ago and at that time the formula
worked fine. :)
the final formula i got is this one:
videobitrate = (1024*1024*finaldim - synchbitrate*length -
audiobitrate*128*length*0.9765625 + base) / ( kscarto + length*128 );
where:
videobitrate is the video bitrate in kbps you have to pass to the codec;
finaldim is the final file (the one you want to create) dimension in MB;
length is the movie length in seconds;
audiobitrate is the audio stream bit rate in kbps;
and where the constants values are:
const long double kscarto = 18153.4591194968553459119496855346;
const int base = 3703801;
const int synchbitrate = 604;
Of course in this result there is no theory at all, it was achieved just
trying some compressions. Let me know if it works.
ciao,
lik
--
Non sono fiero di molte cose terribili che ho fatto... e quelle di cui
vado fiero sono molto peggio!
- Boe
