Cornfused bout file size

Jim H wrote on 12/10/2008, 1:42 PM
A friend wanted a copy of a video for his Ipod that my brother posted on Vimeo. The original file was rendered to MP4 and I assume he used the Vegas settings recommended by Vimeo. So I downloaded the file and thought I would do this friend a favor and re-render it for Ipod at 640x480 letterboxed. The original HD file was 29MB and to my surprize the Ipod version, using Vegas default settings for Ipod, was a whopping 59MB!

What am I missing? And what settings would I adjust to at least get it back below the original file size?

Thanks.

Comments

John_Cline wrote on 12/10/2008, 1:47 PM
Filesize is determined entirely by bitrate. Length of the file in seconds multiplied by the bitrate per second = final file size. What is the length of the video?
Jim H wrote on 12/10/2008, 1:52 PM
The video is 6:30 minutes. I tried changing the default settings from Best to Good and it had no effect that I could see... as you stated, I didn't change the bit rate.

The default is set for Variable Max of 768,000 and Average of 512,000. Per your formula 390 seconds x 512,000KB/SEC average bitrate = 199,680 KB. This does not equate to the 59MB file size I'm getting?

I tried setting both max and average to 198,000 and the file size came down to 13MB. Right direction, but the actual playback size of the video also was cut in half. I did not touch the resolution of 640x480. Now I'm cornfused again.

In any case, If that's the default setting, does that file size seem high? or low? I admit I tend to blindly follow Vimeo's MP4 template for everything...
John_Cline wrote on 12/10/2008, 2:03 PM
If the original file is 29MB and your file ended up at 59MB, then cutting the bitrate in half would make the file about 28MB. However, 512,000 for the video and 64,000 for the audio should get you just under 30 MB for a 6:30 piece. You said that you used 512,000 of the video, but what bitrate did you use for the audio?
Jim H wrote on 12/10/2008, 2:08 PM
There are two values for bitrate, max and average. which are you referring to?
I'm rendering now so I can't see the audio bitrate, but I didn't change it from the default.

Right now I'm rendering at a max of 256K max and 198K average.

What are typically good settings for ipod playback?

BTW, I also edited the message above. thanks for the help.
John_Cline wrote on 12/10/2008, 2:15 PM
The average is the only setting that matters as far as file size is concerned. Generally speaking, the max should be set to twice the average. Setting the average and max to the same value gains you nothing.