greeches
09-28-2006, 01:51 PM
How can this be a larger file size than the original source? Where is this additional information coming from?
Demistate
09-28-2006, 07:17 PM
When you are importing with a codec say like DV, it will toss out information, compress it, and re-generate some colors and pictures while decoding. Just like Mpeg-i frames only contain the changes from the previous frame.
While I'm no expert on how codecs compress data to save space, I can tell you that video is a really, really really high bandwith application. Un-compressed video contains all the bits, for each pixel, and depending on the depth you saved the video at (Hello 24 Bit Color!) you could have extra data, representing your 8-bit original file.
Here's an example
I only have 8 bits of color data to describe how a pixel is, (255, 255, 255 with the RGB scale)
But if you have it saving as 24 bit color, then you have 65,335 values per channel.
Can you see how the file size can ramp up drastically?
Check out this article (http://en.wikipedia.org/wiki/Chroma_subsampling) to see the differences between chroma sampling, which DV is a 4:1:0 codec, while uncompressed is 4:4:4