Captured video creating too large files

[MarcosJP]

Captured video creating too large files

I wonder if I'm doing something wrong or if it's just like this. I've captured two one hour home videos and wanted to fit them in a DVD-R. However, one of the videos resulted in a 2.3Gb file and the other resulted in a 2.5 Gb file. So they won't fit in a 4.7 Gb DVD-R.

Strangely enough, a 2 hour video captured from a TV special (s-video) resulted in a 2.2 Gb, and this time with stereo sound...

These are the settings I used for the home video captures:

720 x 480 MPEG2
5.00 Mbit / second
48.000 Khz, 16 bit, mono
Motion estimated quality: 90

I used ATI's MMC 7.7

Any hints?

Greetings!

Marcos.

[furdog]

(5.00 Mbits/sec)/(8 bits/Byte) = 0.625 MBytes /Sec

file will be 0.625 MBytes/second

1 hour = 60 minutes = 3600 seconds

0.625 MBytes/Sec * 3600 Sec/Hour = 2,250 MBytes/Hour

The bitrate will control the file size. The other settings will affect the quality of the picture at same bitrate.

If you find settings which improve the quality, you might be able to use a lower bit rate to get a smaller file size.

[ZippyP.]

(5.00 Mbits/sec)/(8 bits/Byte) = 0.625 MBytes /Sec

file will be 0.625 MBytes/second

1 hour = 60 minutes = 3600 seconds

0.625 MBytes/Sec * 3600 Sec/Hour = 2,250 MBytes/Hour

The bitrate will control the file size. The other settings will affect the quality of the picture at same bitrate.

If you find settings which improve the quality, you might be able to use a lower bit rate to get a smaller file size.

Check out the brain. Actually, I was going to do the same thing.

MarcosJP: Basically the filesize is affected by 2 things, bitrate and time, and a higher resolution requires more bits/sec to maintain quality. Lowering resolution sacrifices sharpness but if you're capping from a camcorder you may not need that high a setting. You could lower both the resolution and the bitrate and not notice any difference. Your choice.

[MarcosJP]

Thank you for your quick response!

Well, what resolution may I use for a DVD - 480 x 480? I tried this the other day but the DVD burning software (DVD Movie Factory) complained the file was not DVD compliant.

And if I lower the bitrate to 4.0 won't I lose sharpness?

Thank you VERY MUCH for the math info.

Greetings!
Marcos.

[ZippyP.]

I don't do DVD-r's myself but I will try and answer, as the theory is the same as for VCD/SVCD. Although the lower resolution may not make for a "compliant" dvd, you should still be able to use it (Check out the What is DVDr section at the top left.) Anyone else care to comment?
You should try to match the resolution of your mpeg to your source, whatever that may be (Vhs, Avi, DV etc.). Too high a resolution causes problems as you cannot create pixels when there was none. It will introduce artifacts. Lowering the bitrate will have an affect (negative) but it really is in the eye of the beholder. The best thing is for you to do some tests at different resolutions and bitrates and judge what is acceptable to you. In general, no matter what format, there always seems to be a trade off between quality and filesize.

[furdog]

At the same resolution and settings, reducing bitrate will reduce picture quality (the price for being able to fit more on the disc).

What is DVDR in the upper left gives a good overview of the formats. 480x480 MPEG2 is SVCD compatible, but is not on the list of resolutions for DVD standard. You will find differetn software and standalones vary in their toleration/support of non-standard (or uncommon) configurations.

720x480 is the typical standard, but there are others listed (I have not tried them, so don't know the success rate using them). I have read of people using the lower resoultion for captured TV episodes, where there was nothing to gain from higher resoultions, and they picked up longer playing time per disc).

In terms of bit rate, if you want to really get into it you would have to do a lot of tria and error. Cut back the bit rate until you see the difference. Then tweak any encoding setting you can (read what they do) and see what works best with the types of movies and content you are encoding - if can improve quality, then can step down the bit rate more. Single versus multi-pass encoding, Constant Bit Rate versus Variable Bit Rate will all impact file size.

For me, I try to go as high a bitrate on a PVR-250 hardware capture card as I can fit on the disk for what I am going to encode. I don't have the time available to devote to fully experiment.