Need help calculating DVD compression (hw question)...

[JohnCU]

Question -

To be able to fit 133 minutes worth of video on a single-sided single-layer DVD, a fair amount of compression is required. Calculate the compression factor required. Assume that 3.5GB of space is available for the video track, that the image resolution is 720x480 pixels with 24-bit color, and images are displayed at 30 frames/sec.

The amount of data the DVD can hold (in bits/sec):
3.5 * 2^30 bits / 133*60 secs = 470939 bits/sec

Here's where I get confused. The solutions manual has this for amount of data to be compressed:

720*480*24*30/8...why did they divide by 8?

 

[Homerboy]

BITS TO BYTES
Edit: er rather vice versa

 

[pulse8]

Make your life easier:

http://www.videohelp.com/calc.htm

 

[JohnCU]

wouldn't you multiply by 8 to convert bytes to bits?

 

[daniel1113]

The 8 represents an 8-bit byte.

 

[JohnCU]

don't you want the final answer in bits/sec though?

 

[3chordcharlie]

I believe your answer of 470 000ish is in B/sec, not b/sec.

You could encode 133 minutes on a CD at better than 470kbps.