My digital camera needs 1GB of memory to record 15 minutes of 600 x 800 pix movie in AVI format. So how can a DVD (4.7 GB) hold 120 minutes of high quality movie?
2007-03-01 00:28:18 · 5 answers · asked by Dr Who 1 in Consumer Electronics ➔ Cameras
600*800=480000 pixels
480000*2=960000 bytes/frame
960000 =937.5 KB/frame
937.5*25=23437.5 KB/sec
23437.5/1024=22.88818359375 MB/sec
That is just uncompressed size of 25 frames per second 16 bit colour. roughly 22MB
1000/22 = 45.45seconds on 1000MB (typical 1gig card)
So you can see to get more than that you need to use COMPRESSION.
Your camera seems greedy at 15 minutes per Gigabyte. It's using roughly one megabyte per second! Thats 8 Mega-Bits.
A typical DVD is using between 4 and 8 mega bits per second 15 minutes times 4.7 = 70.5 minutes on a single sided DVD. BUT comercial DVD is Dual Layer i.e. 9 Gigabytes which would be 141 minutes at 8 megabits per second. So your camera is comparing quite well to a typical DVD.
Copied single layer DVD movies are compressed at a lower bitrate, so they can fit.
Bear in mind that the European PAL DVD format is lower resolution than your 800*600 - they are 720*576. As a consequence they need less memory space to store the uncompressed image.
Thank god for Mpeg2 (video) and AC3 (audio) compression, or we would need huge discs to watch our movies on.
As far as file size goes, the actual format (Mpeg or AVI) doesn't matter, it's the bitrate that determines file size at the end of the day.
Hope that helps, I've fried my brain now.
2007-03-01 01:13:48 · answer #1 · answered by 👑 Hypocrite 7 · 0⤊ 0⤋
a DVD holds 4-8 GB of memery. Also AVI is a very memery intesive format. And High quality for DVD is kinda miss leading. Compared to VHS DVD is high quality. If you want to get high quality then switch to mpeg3 or something like that the format they use for DVD. AVI just plain sucks for movie and sound files but you can make little ones and it is cheaper to buy and do than the mpeg movie recorders.
Hope this helps
-David-
2007-03-01 00:37:27 · answer #2 · answered by David M 2 · 0⤊ 0⤋
the dvd and the 1gb memory card are different
a laser is used to put the info on the dvd allowing it to hold more capacity
2007-03-01 00:32:39 · answer #3 · answered by links305 5 · 0⤊ 1⤋
different bitrate, different compression, different resolution
avi is just a filename, it says nothing of the way the file is compressed etc
2007-03-01 00:32:39 · answer #4 · answered by rykkers 3 · 1⤊ 0⤋
Magic.
2007-03-01 00:31:46 · answer #5 · answered by Anonymous · 1⤊ 3⤋