benefits of constant bit rate versus variable?

[Dave Friend]

Jeff,

You need to set-up each movie as a seperate encode project and submit each project to the batch function.

Hope this helps.

Be sure to check out the Cinema Craft Encoder too. Personal opinion is it’s the best available.

Dave

[Jeff Nelson]

Thanks, Dave. What makes Cinema Craft best, in your opinion?

[Dave Friend]

Jeff,

My opinion is based on an encoder “shoot-out” I devised and conducted in-house. A short sequence was cut together from a variety of sources. It included scenes that can be problematic for mpeg encoders – shots with fast motion, slow zooms on highly detailed and moving subject matter, computer generated animations, text on a subtly gradated background, text keyed on video, and slow dissolves between scenes with opposing motion. The edit was exported as an uncompressed avi. All the videotape sources were captured uncompressed via SDI. All animations were rendered to uncompressed files from the application they were created with.

The sequence was run through every encoder I had or could lay my hands on. The encoding parameters used (bitrate, GOP size and structure) were identical for each encoder. They were, in no particular order:
Canopus ProCoder 2.0
TMPGEnc 3.0 XPress
MainConcept (as found in Adobe Encore)
Ulead (in DVD Workshop 2.0)
Ligo (as found in discrete edit 6.5)
Cinema Craft Basic (version 2.69.01.10)

It was also output to Digibeta and encoded through a Sonic Solutions SD-1000 real time encoding card

[Jeff Nelson]

By the way, Dave, on this answer you gave — I downloaded the trial version of Tsunami and the batch function is grayed out, so I guess if I’m going to do batch work I need to buy the full version. Can’t see how to get the batch thing working here.

[Ron Shook]

Friendly Dave,

Hey, Ho! Nice thread. Liked your shoot out!

This entire thread has dealt with the value of CBR when space isn’t an issue in terms of available DVD space.

Can you or anyone say whether CBR is also preferable because it has a contant bit rate and is less likely to choke a marginal player because the bit rate is all over the place with VBR, particularly a VBR where minimum and maximum rates are acres apart?

Ron Shook

[Eric Pautsch]

” Can you or anyone say whether CBR is also preferable because it has a contant bit rate and is less likely to choke a marginal player because the bit rate is all over the place with VBR, particularly a VBR where minimum and maximum rates are acres apart? “

This is how I think..but many will argue it. My worry lies in the bitrate spikes that ALL encoders can produce putting you over the spec limit. You can put about 90 mins of MPEG on a DVD-5 with a CBR rate of 6mb/s. It just sound logical to me to provide a nice “clean” constant bit when its available.

[Dave Friend]

[Ron Shook] “Can you or anyone say whether CBR is also preferable because it has a contant bit rate and is less likely to choke a marginal player because the bit rate is all over the place with VBR, particularly a VBR where minimum and maximum rates are acres apart?”

Hi Ron,

I can not say with certainty. My gut feeling is that wide swings in bitrate should not cause any particular problem even for marginal players. The max rate of the file is readily available to the player and it should be setting up buffers accordingly.

I have not seen any more problems with VBR than with CBR in regards to playback skips and/or picture break-up. If the situation you wonder about was common then I would expect to see more problems with VBR than with CBR discs.

In either case I think playback problems are usually because of throughput issues – the player just can’t pass the data fast enough. (Data Constipation?) It could be because the system can’t process the data fast enough. But my feeling is that most of the time it is because the player has trouble reading the disc. That can happen at any bitrate but problems do seem to get worse as the bitrate increases.

Dave

[Ron Shook]

Dave & Eric,

Well, sounds like I should just use what I have to within commonly accepted practices and not worry further. Excellent!

Ron Shook

[Daniel_l]

Dave,

Just to clear up any misunderstandings, I was referring to a multi-pass VBR encode, not single pass, as I think you are.

DL

[Dave Friend]

[daniel_l] “I was referring to a multi-pass VBR encode, not single pass”

Hi Daniel. I was referring to multi-pass VBR.