# Voltage calculations

• posted

Please help a student with the technique to solve this problem!!!! A short digitally-encoded video clip is saved as a compressed file of

3,264,000 bytes. If the compression is 12:1 and there are 60 frames/ sec in the video clip, and each frame has a resolution of 128 x 170 RGB pixels (24 bits/pixel), then: (a) How long does it take to play the clip? (b) What is the uncompressed data rate in bits/sec?

• posted

What course is this for?

If it's for a fairly general course, you're probably just expected to multiply and divide the numbers given to get the desired answer. The actual math is trivial; the only interesting part is figuring out what to multiply by what. That's pretty simple too, but since figuring it out is the only value you'll get from the question, I won't spoil it. How far have you gotten on your own?

On the other hand, the real world of video often involves multiple steps that each compress the data somewhat, and the "12:1" compression figure is sometimes not a measurement from raw data off the sensor to recorded output stream. In that environment the question gets trickier, because you have to figure out the processes involved in more detail. But this question sounds like it wants to ignore all that and present a simple scenario with a simple solution.

Dave

• posted

On Mon, 26 May 2008 09:12:55 +0200, Smarti wro= te:

3.264.000 bytes compressed compressed size * compression * 8 (convertion to bits, assuming 8-bit/by= te =

system) =3D decompressed size

3.264.000 bytes * 12 * 8 =3D 313.344.000 bits

With 24 bits/pixel and 128*170 pixels per frame and 60 frames per second= :

24 bits/pixel * 128 pixels * 170 pixels * 60 1/second =3D 31.334.400 =

bits/second

Now: a) unencrypted size/stream =3D time

313.344.000 bits / 31.334.400 bits/second =3D 10 seconds

b) see above for uncompressed datarate (the stuff with 24 bits, pixels squa= re =

and 1/second...)

Could have done it yourself, didnt you?

• posted

Answer: 5 volts (see subject line).

• posted

On Mon, 26 May 2008 21:21:59 -0700 Paul Hovnanian P.E. wrote: | Smarti wrote: |> |> Please help a student with the technique to solve this problem!!!! |> A short digitally-encoded video clip is saved as a compressed file of |> 3,264,000 bytes. If the compression is 12:1 and there are 60 frames/ |> sec in the video clip, and each frame has a resolution of 128 x 170 |> RGB pixels (24 bits/pixel), then: |> (a) How long does it take to play the clip? |> (b) What is the uncompressed data rate in bits/sec? |> |> Please help??? | | Answer: 5 volts (see subject line).

He asked two questions, not one. The 2nd answer is 3.3 volts.

• posted

Hint: a) 10 seconds b) 31,334,400 bits/sec