The quality of long DVDs

[Berzelius]

I've got a number of mpg files that I am using to produce a DVD. The total length will be about 90 minutes. Searching this forum I found that the standard video bit rate is 8000 kbps and that it will drop off for DVDs longer than 60 minutes.

I took the mpgs and I was pleasantly surprised to find that there was no need to change the bit rates of the mpgs; VS X7 did all the hard work and produced a usable (as far as I can see) iso file without any need for further action from me.

The original mpg files all had a maximum variable bit rate of 8000 kbps and by importing the DVD into VS X7 I found that it had a variable maximum bit rate of 6346 kbps.

The DVD quality seems quite reasonable and I'll do a bit of visual checking of the DVD against the original mpgs, but it's quite difficult trying to compare things when you have to switch from one to the other.

My question is what, in your greater experience, would the bit rate have to drop to to produce noticeably poor results? There's nothing particularly rapid in the video clips, the fastest is my grandchildren running and kicking footballs.

[Ken Berry]

The 6346 kbps bitrate is certainly consistent with a video which is 90 minutes long. The general rule of thumb is that you can fit around 70 minutes of video onto a single layer DVD using 8000kbps and Dolby audio. Quality is high. You can fit around 100 minutes using around 6000 kbps and have good quality. And around two hours with a bitrate of 4000 kbps, though the quality would be no better than VHS tape. Below that the quality would drop off quickly, though when it might become unwatchable will always depend on the individuals watching it.

[asik1]

Berzelius, the poor results will be not much from the datarate as from the 60" screen you use showing SD video.

[Berzelius]

Thanks for the replies. I've now got a bit of extra material that I want to fit in, but I reckon I can keep it below 100 minutes.