Thanks Bob,
No, they are not noisy. They are dark stage lit scenes, but not noisy in the AVI file. It is the details that are present in the AVI files that are being lost in the Mpeg 2 compression. I wanted to experiment with CBR to see how it looks, but not at the expense of compatibility.
Thanks,
John

I cannot see why the mpeg-2 compression is causing you to loose detail. Why not just render a small bit at a higher bitrate and see if that makes a difference.

What might be the problem is the way the players shift the video levels. Basically they legalise the output, try putting a knee in the blacks with the color curves before encoding, that might solve your problem.

2 Pass encoding is the way to wring the most out of the encoding BTW.

Bob.

Bob,

In darker footage, compression causes a loss in detail. The higher bitrate would solve some of that problem, and it may very well be that VBR will yield better results than CBR.
I wanted to try CBR and I know that a few people in the past like John Meyer and John Cline have posted that they use CBR at least some of the time.
But I don't know about maximum CBR vs compatibility. I just hate to find out the hard way (customer returns). That is why I posted this question.

John

Again, this is using Vegas 4 + DVDA 1

Well max bitrate limits should be the same for VBR or CBR so from my experience you should be fine upto 7.5Mbits, probably with CBR you could push it to 8 Mbits without problems.

Are you really certain though you're not loosing out to noise?
I've yet to see 'dark' footage that doesn't have some noise.

Try this test, mask out the black parts of a minute of footage with solid black and see how the detail in what's left fares. If that improves things then you have a noise issue.

Also if this is the issue it means the encoder is running out of bandwidth. If you look at your mpeg file with the bitrate viewer you'll see the rate stays pretty close to what you've set it at. In this case VBR gains you nothing.

As you only have Vegas 4 then I think 2 pass isn't an option either.

Bob.

I have never tried the bitrate viewer. Got a link Bob?

John

The maximum allowable bitrate for DVD's is 9.8 Mbits/sec. That's both audio and video combined. All DVD players must meet this standard.

If the video is shorter than about 74 minutes, I just use 8 Mbits for video and use 192Kbit AC3 audio. That gives me a lot of headroom before hitting the 9.8 Mbit limit. Some MPEG2 encoders will occasionally "spike" over the set CBR bitrate, so using 8Mbits leaves some additional "headroom." I had one particularly difficult video (lots of detail and continuous high motion) and I encoded it at 9Mbits with 192Kbit AC3 audio. I never got any complaints, it seemed to play fine on everyone's DVD players.

Bitrate Viewer

John

Thanks for that John.
I will try 8 Mbits CBR and run some tests with a DVD-RW on several players.

John

I also use CBR 8Mbits for all projects short enough to fit. I have had no problems.

JAB

Encoded the 1 Hr 9 Min video at 8000 KB/s CBR and the results were greatly improved over the VBR described above.
The Bitrate Viewer showed a peak at around 8300 and an average bitrate of around 7500 with the Mpeg 2 encoded at 8000 CBR.

I burned on a 1x DVD-RW and played it on two DVD players. Both were Panasonics so the compatibility test may be invalid on those because Panasonics will play a tuna can lid flawlessly.
The video was crisp and clear even in the areas the VBR rendered as too dark.
Unfortunately it took up the whole disc with NO Menus included as I knew it would. I just wanted to see of it would make a noticeable improvement and it did. Very noticeable.
Now I will have to see if it plays well in other machines and then start moving downward until I can include the menus and not exceed 95% disc capacity. There will probably be around 12 motion thumbnails on two menu pages so I can probably get away with a CBR of 7500 KB/s. Hopefully that won't be that noticeable a drop in quality.
How do you think a VBR of 6000 Min, 8000Max, and 7500 Average would stack up against a CBR of 7500 for example?

John

From the little I know you don't gain much using VBR without going to 2 pass (or more) encoding. I think with the figures you're looking at you'll get the same result with CBR or VBR, I don't see why you'd want the minimum so high, not that it's going to matter much unless there's areas in the video that can be handled by a low bitrate.
I know I keep repeating this but in my experience the biggest single factor affecting the losses due to mpeg-2 encoding is the quality of the source. I've started out with everything from DigiBeta down to worn out VHS. Going from a shot for broadcast DB tape to DVD you'd have to look damn hard to pick the difference, starting from worn out VHS it's a major battle not to have the thing fall apart badly.
I'd suggest upgrading your Vegas+DVDA to get 2 pass encoding would be a good step and I seem to recall the latter versions of the MC encoder even at single pass performed better.
Bob.

...I can include the menus and not exceed 95% disc capacity.

Just a thought here John. Go ahead and do your render at whatever maximum you want and then use DVD Shrink to squeeze it back down to the right size and see if the quality is still acceptable to you. You have nothing to lose except for some encoding & burning time.

Mike

CBR will ALWAYS look better than VBR. It's a no-brainer. You can get slightly more video on a disc using VBR, but that's the only benefit. I stopped using VBR a year ago for the exact reason you mentioned: dark scenes. If the project length will allow it, I usually encode around 7800.