Quantcast File Size Prediction Sometimes Not Accurate Using Vmesquita? - digitalFAQ.com Forums [Archives]
  #1  
09-06-2003, 10:47 AM
rs008f rs008f is offline
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I'm currently using vmesquita's quide and calculator to predict file sizes but sometimes the total of the final sizes turned up to be much smaller than expected. Take for example, I was trying to encode a KDVD of 325 minutes video with 160kbps audio. Using vmesquita's calculator, it gave a sampler size of 40.79 MB. I tweaked the Q factor in CCE until the sampler size is 40.5MB which is pretty close and I always do it smaller since I don't want to face the situation where it can't fit onto the DVD-R. But now the actual final size of the movies along with audio add up to 3.6GB which leaves a lot of space to fill in. Is there a more accurate way to predict final video file sizes? I'm converting some episodes Divx cartoons, the only difference with vmesquita's script is that I deleted all the filtering lines.
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  #2  
09-06-2003, 04:12 PM
Dialhot Dialhot is offline
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I guess your problem is that your movie is too long.
I don't know the Vmesquita'a method but generally we take a constant number of frames within all the movie length to make the encoding sample. If you take for instance 2000 frames in a file a 120 min, you will be more accurate than if you take 2000 from a file of 360 min.
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  #3  
09-06-2003, 05:25 PM
Reno Reno is offline
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OK

1) Total length of source in seconds

2) Length of the sample in seconds

3) Divisor (divide step 1 by step 2 to get this number)

4) Your video budget (subtract the file size of your audio file from 800)

5) Target sample size (divide step 4 by step 3)

6) Hit that number, and encode.

------------------------------------------------------------------------------

My last two encodes have both landed at EXACTLY 800mb using this method. That isn't unusual for me. Until someone comes up with a tool that can duplicate my results, I'll stick to this...
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  #4  
09-06-2003, 07:29 PM
Dialhot Dialhot is offline
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Quote:
Originally Posted by Reno
2) Length of the sample in seconds
That's exactly what I wanted to point out !
As generally the sample length is always the same (for instance, 2 min with CQMatic), the more your movie length is, the less you are accurate.
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  #5  
09-07-2003, 05:09 AM
vmesquita vmesquita is offline
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Are you sure you are doing the GOP factor right? Please remember that after determining the GOP, you must use it in the calculador and in the sampler line! I never got a error bigger than 3%, so I think this result of yours is very wired...

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