Do you Divide by the Factor .98 or Divide by .98? - digitalFAQ.com Forums [Archives]
 digitalFAQ.com Forums [Archives] do you Divide by the Factor .98 or Divide by .98?

#1
02-14-2003, 09:24 PM
 Paul0889 Free Member Join Date: Nov 2002 Posts: 102 Thanks: 0 Thanked 0 Times in 0 Posts
i'm encoding a movie called ginger snaps. so after you do
frames/movie length/24 *sample size, do you divide by the factor .98 or divide by .98?
Someday, 12:01 PM
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#2
02-14-2003, 09:59 PM
 kwag Free Member Join Date: Apr 2002 Location: Puerto Rico, USA Posts: 13,537 Thanks: 0 Thanked 0 Times in 0 Posts
Hi Paul0889,

You multiply the sample file size by .98
The formula would read like this: MPEG size = ((Total frames/MovieTimeInMinutes)/24) * MPEG sample file size * .98

-kwag
#3
02-14-2003, 10:11 PM
 Paul0889 Free Member Join Date: Nov 2002 Posts: 102 Thanks: 0 Thanked 0 Times in 0 Posts
so then when you predict you sample size, your going to have to guess something a little higher right? See my predicted sample size is 11.63 but if i multiply by .98, it doesn't come out to 727.9, the amount of disk space left. So i have to raise the sample size a little higher right?
#4
02-14-2003, 10:19 PM
 kwag Free Member Join Date: Apr 2002 Location: Puerto Rico, USA Posts: 13,537 Thanks: 0 Thanked 0 Times in 0 Posts
Quote:
 Originally Posted by Paul0889 so then when you predict you sample size, your going to have to guess something a little higher right? See my predicted sample size is 11.63 but if i multiply by .98, it doesn't come out to 727.9, the amount of disk space left. So i have to raise the sample size a little higher right?
That is correct
When you get your predicted sample size of ~11.63, multiply it by .98 and multiply by 60 ( if you're encoding at 23.976 ) and that will be your actual final file size.

Edit: Actually just multiply your estimated sample file size (11.63) by .98 and by 60 and that's your final file size.

-kwag
#5
02-14-2003, 10:29 PM
 Paul0889 Free Member Join Date: Nov 2002 Posts: 102 Thanks: 0 Thanked 0 Times in 0 Posts
what if i'm encoding at 25fps? would i still multiply by 60? Also, since i multiply by 0.98 and 60, i'd have to pick a higher sample size since
11.63*.98*60=684. So then i'd have to raise the sample size to about 12.35 in order to get it equal to 727.9 right?
#6
02-14-2003, 11:35 PM
 kwag Free Member Join Date: Apr 2002 Location: Puerto Rico, USA Posts: 13,537 Thanks: 0 Thanked 0 Times in 0 Posts
Quote:
 Originally Posted by Paul0889 what if i'm encoding at 25fps? would i still multiply by 60?
No.
Quote:
 Also, since i multiply by 0.98 and 60, i'd have to pick a higher sample size since 11.63*.98*60=684. So then i'd have to raise the sample size to about 12.35 in order to get it equal to 727.9 right?
The 60 works only for 24fps, because if you look at the formula: MPEG size = ((Total frames/MovieTimeInMinutes)/24) * MPEG sample file size no matter what run time the movie is, it will always divide by 24 which is the GOP size and it's exactly one second. So for NTSC Films encoded at 23.976fps we're actually taking one snapshot every minute. That's why we can multiply by 60. Sorry, I didn't know you were encoding PAL What you can do, this is just a test , is change the MAX frames on the GOP to 25 and the sampler line to read Sampler("Length=25") and then it will apply. So your formula for PAL would read: MPEG size = ((Total frames/MovieTimeInMinutes)/25) * MPEG sample file size
Now you can multiply by 60, because the Sampler is talking 25 frames every minute, and the GOP size is also 25. Give that a shot. It makes the calculations much easier. Just (CD Size - audio size) / 60 = your sample size. Example: ( 800 - 100 ) / 60 where 800 is CD size and 100 is audio size

-kwag

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