60 min video on a disc, what?

cheroxy wrote on 12/19/2003, 4:12 PM
I have always had a question about what DVD cases say regarding video quality. If you buy a disc with a case they paper in it shows a table with different recording qualities and how much you can fit on a disc at that quality. They say, high quality - 60 minutes, sp = 120, LP - longer...

How is that possible? I record everything in SP and render it at the highest quality possible. When I do that I can always fit just under 2 hours on a disc. The only way I can see that could be true would be if you did your render at a CBR of 6500 or something. Even then, would that only allow 60 minutes of video? Where are they getting that number from?
thanks for any answers,
Carson

Comments

Spot|DSE wrote on 12/19/2003, 6:43 PM
Your question is a bit confusing, but hopefully this formula helps? There are also bitrate/length calculators all over the web.

600 divided by project minutes is a good rule of thumb for the total bitrate in Mbps of a 4.7 GB disc. The reason it works is the following;
4.7 GB * (1 min / 60 sec) * (8 bits / 1 B) = 624 Mbps*min
It should be noted that the rule of thumb is only relative to 4.7 GB discs.
As an example, for a 90 minute project 600 divided by 90 equals a bitrate of 6.6 Mbps.
cheroxy wrote on 12/19/2003, 7:33 PM
Thanks. That is the same train of thought that I was using.

Sorry about the confusing post, I posted from a different computer after talking with a FCP editing friend about this issue.

OK on the paper in the TDK DVD jewel case it says:
Recording quality Recording time per disc
HQ highest quality 60 minutes
SP standard play 120 minutes
LP long play 180 minutes
EP extended play 240 minutes

My question is: what are they refering to when they say that doing a disc at HQ only allows for 60 minutes of play time. According to my (and your) calulations you would have to have a CBR of 10.0 Mbps for only 60 minutes of video! As far as I know that wouldn't work on any standard DVD player, too high of a bitrate. For that reason, how could you be limited to 60 minutes of video for a 4.7 GB disc?
thanks

PS. Spot, I enjoyed your visit to the DV guys show. I think having your clout associated with Vegas does a lot for its credibility.
farss wrote on 12/19/2003, 10:14 PM
I don't really know where they dream those fiqures up from either. I think they refer to what you can expect from one of those STB DVD burners. Also if you use PCM or ac3 audio makes a BIG difference to what will fit on a DVD, to say nothing of CBR versus VBR and how good the encoder is.

I guess putting all that on a label would be just too confusing
Spot|DSE wrote on 12/19/2003, 10:32 PM
I think some product manager at TDK needed copy for the label, and so swiped text from a VHS tape, and pasted it in a format that he understood. Probably has never burned a disk in his life...It simply makes no sense.
But hey! It spawned an intelligent thought and subsequent question...
cheroxy wrote on 12/20/2003, 5:29 AM
I had to check to see if my logic was off. I agree, that was probably transfered over from VHS.
thanks