WMV File Size issue ??? for Spot

waketek wrote on 1/18/2005, 4:35 PM

OK, This is wierd. I created some streaming media for a Company. Here are the specs bit rate = 512 kbps Video size = 320x240 Aspect Ratio = 4:3 Audio = 64kbps , 44kHz, Stereo 1-pass CBR Total length is 06:03 File size 26MB

I used the same project and added some more video tracks with Text. After rendering the project to the exact same specs as before I seemed to have lost 4MB the new file size is 22MB and yes the specs are the same total length is the same.....Video looks great so no worries but I just cannot figure out how the file size got smaller ????? Any ideas?????

Comments

waketek wrote on 1/18/2005, 5:52 PM

Anyone have any ideas?

Spot|DSE wrote on 1/18/2005, 6:00 PM

Something couldn't have been the same. File size is determined by length and bitrate, but the number of keyframes would make a difference too. It may be that you had fewer keyframes in the new version than the old version?

waketek wrote on 1/18/2005, 6:12 PM

I have checked and double checked evrything. Bitrate and and length are identical. I added a bunch of text on 4 new video tracks to the original project. I have not created in Automation or Animation so no keyframes. I have 10,895 frames in both projects. The only thing I did was add text to the video project and changed the velocity of two scenes to create a slow mo but the scenes themselves were not shortened. It is not a huge deal but just has me puzzled. There have been projects that I could have really benefited from this however this is not one of them. Thanks for the Reponse Spot! We talked for a bit back at the tour and training in Seattle it was good talking with you again.

Spot|DSE wrote on 1/18/2005, 6:52 PM

The Keyframes aren't related to anything you'd do. It's keyframes set by the encoder as to where changes in frames are at, and how it should manage them.
Check this article out. Very dated, but relevant.
http://www.cvc4.org/mentorworkshop/streamingmedia/intro2streaming.htm

waketek wrote on 1/18/2005, 7:58 PM

Thanks for the link it's been a while since I read that but it adds up now. Thanks for the help.

Liam_Vegas wrote on 1/18/2005, 8:31 PM

If you used a constant bit-rate template then there is a VERY simple equation that will tell you if everything is right.

Bit rate / 8 * seconds = File size in Kilo Bytes

Bit Rate = 512Kbps
Length (seconds) = 6 minutes 3 seconds

512 / 8 * ( 6 * 60 + 3) = 23232KBytes = 22MB

So.. whatever is going on.. your current file size seems correct. The first time you did it.. I suspect you chose a slightly different template (maybe the 512Kb Variable bit-rate).

Either way... your current size... is just fine. If it looks OK... then why worry yourself any further?