Calculating AVI size to fit on a DVD in MPEG format

[mattlynne]

Can anyone suggest a simple formula to work out how much raw footage or AVI file would be needed to fit onto a standard 4.7GB DVD (compressed into MPEG2). I tried to compress an AVI file of 22GB (just over one hour of SVHS home film) but this compressed to 8GB. This took me two hours to render, only to find out it was too large. I can't find any helpful tips on percentage compressions anywhere.

PS I am new to editing!

[Akai Rounin]

Mein Gott!

22 Gigabytes for ~*one*~ hour of video? WOW. Truly amazing. Dude, that's big - really BiG. It's ~*still*~ 8 Gigabytes after compression? OK then, let me see if I can help you...

This is video captured from videotape (S-VHS), right? Can you tell us a few more details about this file, please? What audio and video codecs were used to capture the video? What bit rates were used for each? What is the frame size in pixels? How many frames per second is the video? How much hard drive space do you have available/total? What in the world did you use to capture the video to your PC?

Honestly, I have no idea how your AVI ended up so huge. Look at this:

Your Original file

22 Gigabytes - 1 hour
375 Megabytes - 1 minute
6.25 Megabytes - 1 second

Your Reduced file

8 GB - 1 hour
136 MB - 1 minute
2.25 MB - 1 minute

All these numbers are really, very big. Especially so for a videotape source. Most of the guides here at VCDHelp.com suggest that television or videotape be captured at a maximum of about 352x480 pixels. Though it is possible to use higher horizontal resolutions for capture, the consumer NTSC videotape format is only about 352x240 pixels itself.

Truly, you should be able to preserve the full quality of your original source without using the full capacity of a DVD-R/RW. If you still want to do it though, that can be managed. There are numerous audio/video bit rate calculators on the internet. Some are listed in the Tools | Bitrate calculators section of this site. There are others at sites like DivX.com or DivX-Digest.com... Also, unless you are running out of hard drive space (which wouldn't surprise me), it isn't really necessary for your AVI file to be the same size as your final MPEG-2 file. Often the source AVI is bigger than the final MPEG-1/2 file, though not quite this big a disparity.

Anyway, you want the file to be on a 4.7 GB DVD. Just for the sake of allowing for error, let's just say we try for making it 4.5 GB. We'll assume that you will extract your audio from the AVI as a WAV file before encoding. At around 10 MB per minute, this would make a 600 MB WAV. This leaves 3.9 GB for video. Using the same process as before, we can determine how much bandwidth would be required for video:

Video Target Size

3.9 GB - 1 Hour
66.6 MB - 1 Minute
1.11 MB - 1 Second

Now, video encoding rates are usually expressed as Kilobits per second. Why such small units when dealing with such huge files? I don't know, it makes no sense to me either. Anyway, a Kilobit is 1024 bits... There are 128 Bytes in one Kilobit. There are 1024 Bytes in one Kilobyte and 1024 Kilobytes in one Megabyte.

So if you are aiming for 1.11 MB per second video, then that is the same as 9093 Kilobits per second, if my math is correct. 9000 Kb/sec is near the upper range of playback capability for most DVD players. You might want to encode a short MPEG-2 clip, perhaps 3-5 minutes, at various rates (2500, 3500, 5000, 6500, 7500, 9000) to determine which works best for you. Read the numerous guides on this site and take it slow. You will make it through, it just takes time.

Toyoniya Hiyaku, Noromuoy!

Akai Rounin, The Cyber Sage

[mattlynne]

Thanks for the help. In reply to your Q's:
I have a 2.4GHz PC, 120GB hard drive running XP.
My video package is Pinnacle 500DV plus
(which captures analogue as well as digital), and uses Adobe Premiere 6 to process video footage.

I uded Pinnacle AVI to capture the video
My bit rates I think are set at 3.8MB/sec as it is a combined digital and analogue capture card. But being new to this, I honestly don't know.
Frame size is maximum (ie recommended setting by Pinnacle for export to DVD)
Vide rate is 25fps (for PAL)
hard disc size is 120GB and I have 80GB left at present.

Your very helpful hints would suggest that I am capturing video at too high a resoution for DVD and maybe I should reduce the frame size, and possibly bit rate? Is this correct. I only used the data as recommended by Pinnacle and Premiere 6.0 for DVD export.
Thanks once again for helping a poor soul in distress.

Mucho gracias!