Am I nuts? (DVD bit rate)

jeremyk wrote on 12/9/2003, 9:47 AM

I've read repeatedly that DVD quality starts to suffer if you try to get more than about 90 minutes on a disc, so I've been careful to produce my long form stuff (mainly operas) as two-disc sets.

But I decided I wanted a DVD master for producing future VHS copies of the lastest 2 1/2 hour video, and after a couple of tries was able to get it to fit on one DVD with a variable bit rate of 6Mb/s high, 3.7Mb/s average, 192Kb/s low.

Last night I looked at my creation. It looked... fine! Not being able to see the two versions simultaneously, I had to look first at one and then the other, but frankly, I couldn't tell the difference. I was looking at a 31" TV with an S-video connection to the DVD player.

So is it the relatively static program material? My crappy eyesight? I thought I'd be able to see SOME difference. Have other people had similar experiences?

Comments

vonhosen wrote on 12/9/2003, 10:08 AM

I think the quality of your original & the encoder are going to play a large role in this. Also , as you have pointed out, how much action there is in the movie.

I've managed to get nearly three hours on a DVD-R & was very surprised by how good the quality was.

John_Cline wrote on 12/9/2003, 10:41 AM

Essentially, MPEG2 operates by only encoding the differences between one frame to the next. If there isn't a lot of motion or video noise in the program, then it is perfectly reasonable that you could use low bitrates with more-than-acceptable results.

John

johnmeyer wrote on 12/9/2003, 11:54 AM

It really depends ... on just about everything.

I'm still in the middle of a massive VHS restoration project (over 50 tapes). Before I started, I wanted to make sure everything was going to look as good as possible, but obviously I wanted to keep the number of DVDs to a minimum. I tried all sorts of things -- too many to go into here. Bitrate was obviously one of the key variables.

One of the things I found is that some video can look amazingly good at low bitrates -- even down to 4,000 kbits/sec. However, just when you think it's safe to proceed ... you find some video that looks awful at these rates.

My "ultimate" test was video taken on Christmas day from a moving car shooting through the leafless trees in Grant Park (Chicago), looking towards the Standard Oil building (or whatever it's called now). All those branches moving across the skyline and a clear blue sky made for some amazing artifacts. It wasn't until I got to more than 7,000 kbits/sec that the artifacts were not objectionable. Also, I viewed this on a 45" TV. Small monitors are great for color checks, but artifacts often don't show up until you look on a big screen.

Finally, when I did my volleyball project last month, I was able to detect differences right up to 8,000 kbits/sec. Obviously that was lots of action, some of it taken through the net.

Noisy video can also require more bits/sec.

kameronj wrote on 12/10/2003, 6:05 AM

Johnmeyer.....It's the Aon Building (Center) now.

johnmeyer wrote on 12/10/2003, 4:26 PM

It's the Aon Building (Center) now.

What the heck is an Aon? I think it changed to Amoco at one point after some merger or other. But Aon?

pb wrote on 12/10/2003, 8:03 PM

As above. I have a two disc documentary that, alas, must be split 2 hours & 5 minutes and 1 hour 40 minutes, otherwise the first disc makes no sense due to a lack of conclusion. I tried a hardware encode but at the low data rate the result was truly pathetic. Main Concept blows it away.

I read your post about the low rate and another from a helpful guy in another thread, rendered the two parts as AVIs then used super low bitrates and the new Main Concept codec. Also, to save time and disc space, I resorted to DVD Complete. Although I would not call the result "stunning", it is acceptable and the Band Elders will be very happy with the result.

These last two days of rendering hell have convinced me to replace this 1.4 gHz PC with at least a 2.8 gHz, sell the non-Vegas friendly Canopus and upgrade my laptop's USBs to USB 2 and boost its RAM. That way the laptop can earn its keep! We're also going to replace the Pinnacle DC1000DV box with something that has a bit more horsepower and maybe look at the new Matrox RT card. My son has put up with his PII 200 long enough and will enjoy his mum's old PII 500!

Thanks again to all.