Render Size Question

[budwzr]

I am using Sony Vegas 7 Platinum. Does anyone here know why the same source file can be rendered as 640X480 OR 320X240 and both file sizes are EXACTLY the same size? All other render settings are identical.

One would think that the 640 would be larger, right? I'm puzzled.

Thanks for any answers.

Bud

[guns1inger]

Universal rule for video

size = running time X bitrate

You can have two videos, one at 1024 x 768 and one at 320 x 240, and if the bitrate is the same, the file size will be the same. The quality may be marked different if the bitrate is set for the low res video.

[budwzr]

OK, but the render time is 5 hrs at 320 and 10 hrs at 640, why is that? I still don't get it. Can you make an analogy? Thanks

[guns1inger]

What filters etc are you applying ?

Without seeing the source details and knowing what you are doing to it, and what else your PC is doing at the time, it is difficult to make a call on render times.

[budwzr]

I'm rendering to WMV9 VBR 1000 average bitrate

[budwzr]

The source details are Divx 640X480 2500 bitrate 30 fps ADPCM audio.

[budwzr]

PC doing nothing else, overnight renders, no updates or backing up or anything.

[budwzr]

No filters, or transitions, or media fx, just cropped the commercials, butted the clips together, then render

[manono]

Universal rule for video

size = running time X bitrate

He already said that. The resolution doesn't matter. 2 different videos of the same length encoded with the same bitrate will have the same final size. The larger resolution one takes longer because it's encoding more pixels.

Why take four posts to say things that could have just as easily been said in one?

[budwzr]

Because I was trying to catch the same person, and I didn't have all the details handy.

So if I'm losing pixels why is the file size the same?

[manono]

Who said anything about losing pixels?

640x480=307200 pixels to encode
320x240=76800 pixels to encode.

I'm surprised the larger one takes only twice as long to encode, as it contains 4 times as many pixels. Maybe the lower resolution one is being resized or otherwise filtered in some way the larger res one isn't.

Again, bitrate directly correlates with file size and video length. Resolution doesn't enter the picture at all (unless you saturate the codec with the lower resolution encode, which doesn't happen here). If you don't understand it (yet), then don't worry about it.

[budwzr]

I think I get it. the 320X240 is only playing 1/4 of the original pixels. But I can't tell the difference when playing both back on a 32" tv, why isn't it 4 times as blurry or pixelated or whatever?

[jagabo]

So if I'm losing pixels why is the file size the same?

I have a small car that gets 20 miles per gallon. I also have a large car that gets 20 miles per gallon. Each car has 5 gallons of gas in the tank. How far will each car go?

Bits per second is like miles per gallon. It doesn't matter how large the frame size is or or how big the car.