Quantcast Bitrates: CQmatic Too High - digitalFAQ.com Forums [Archives]
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02-11-2004, 07:21 AM
khusru khusru is offline
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before i started using scripts cqmatic worked perfectly, since i started using scripts i get a cq that is too high ( numbers like 79.55 which seem like they coould work but the end result is over 1g),
iv been having to work out the cq manually by seeing how big the file size
is at 1 percent of the encoding process then multiplying it by 100 to see if the size will be okay
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02-11-2004, 07:24 AM
khusru khusru is offline
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what am i doing wrong, all my directorys are short
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02-11-2004, 07:29 AM
khusru khusru is offline
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i just read on a nother post that source avi divx/xvid file size predictions are not accurate, is this true?? does this mean that sometimes cqmatic does not give correct numbers cos of this?
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02-11-2004, 07:36 AM
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you are doing nothing wrong. You just fall in the "critical zone".

The function CQ<->filesize isn't flat. There is a zone where a 0.1 CQ can increase the filesize by 10% ! When you did the same source manually, your CQ was probably near 65 and you were in a zone where the curve is flat. There you can move the CQ by 1 point and increase the file by 1%.

That is why CQMatic seems to fail : it "computed" than 79.55" was the correct CQ but the real one is perhaps 79.45.

You understand ?
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02-11-2004, 07:39 AM
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Quote:
Originally Posted by khusru
i just read on a nother post that source avi divx/xvid file size predictions are not accurate, is this true?? does this mean that sometimes cqmatic does not give correct numbers cos of this?
Yes and yes.
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02-11-2004, 07:42 AM
khusru khusru is offline
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using the long winded method i got a cq of 63.55 which gives me az filesize of approx. 670mb, cqmatic gave me a cq of 79.55,

would u recomment using cqmatic just on the avi without a script and getting a cq and using the cq on the project with a script?
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02-11-2004, 07:57 AM
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Quote:
Originally Posted by khusru
would u recomment using cqmatic just on the avi without a script and getting a cq and using the cq on the project with a script?
A script is always better.
Just go in the window where you can set the CQ in tmgenc and put "20" for B-picture spoilage.
That will bow a little the CQ curve and may be you will fond a better number.
Or you can reduce the range min-max bitrate also.
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02-11-2004, 08:05 AM
khusru khusru is offline
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no, i meant getting the cq without a script and just on the avi using cqmatic, then using this cq on a script in tmpg,

if i use cqmatic on a project with a script the file size is allways out,
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02-11-2004, 08:07 AM
khusru khusru is offline
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thanks again for all the help
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02-11-2004, 08:36 AM
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Quote:
Originally Posted by khusru
no, i meant getting the cq without a script and just on the avi using cqmatic, then using this cq on a script in tmpg,
The CQ won't be correct !!!
If you change something beween CQMAtic and the real encoding, you can alos change the source, the effect is the same.

Quote:
if i use cqmatic on a project with a script the file size is allways out,
Not always ! Change the script, change the source, cahnge something. You are just "bad luck" there. I do avi all the time with no real problems.
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