MPEG-2 Variable Bit Rate Settings

[Mike Kujbida]

All videos I do that are under 70 min. long get encoded at a CBR of 8,000,000.
Anything longer and I use https://www.johncline.com/bitcalc110.zip to determine optimum VBR settings.
BTW, even though the Max goes quite high, I never let it exceed 8,000,000.

I use the default AC-3 setting of 192.
I believe (but stand to be corrected) that 384 is the highest you can go.

*** Make sure you use good media. ***
Taiyo-Yuden and Verbatim and the two most recommended brands.
The cost difference between the cheap stuff and the good stuff (especially if you buy in bulk) is minimal.
Why take the chance of having your hard work not being able to be watched in 6 months because you bought the cheapest discs you could find?

[Michael Spooner]

Thanks for the response. I think I’ll give 8,000,000 a shot. You’ve never had problems with players keeping up?

I had another question about AC-3. Does AC-3 (and more importantly, DVD spec) support 24bit audio? I’m trying to decide whether I need to (or should) dither to 16-bit before converting to AC-3.

[Mike Kujbida]

I’ve been using the 8,000,000 Max setting for years and never had a single disc come back to me for playback errors.

The DVD spec does support 24-bit audio.
From DVDA’s online help (which also answers your AC-3 max question):

AC-3 audio (.ac3)

48,000 Hz
192 Kbps (64 Kbps to 640 Kbps is supported)
Stereo

48,000 Hz
448 Kbps (64 Kbps to 640 Kbps is supported)
5.1 surround

PCM audio (.wav or .w64)

48,000 Hz
16, 20, or 24 bit
Stereo – Uncompressed

96,000 Hz
16, 20, or 24 bit
Stereo – Uncompressed

[James Redmond]

Mike, You use a constant bit rate instead of variable? Sony’s default is variable.

Thanks, James

James Redmond
Dynamic Videos, Inc.
Rogers, AR USA

[Mike Kujbida]

Yes James, I do.
I’ve never been a big fan of using the default settings for almost anything I do in video.

The default settings for an MPEG-2 encode using the DVD Architect NTSC video stream are 9,500,000 / 6,000,000 / 192,000.

A number of different users have complained to Sony for a very long time that the Min.setting of 192,000 is far too low.

As I said, I use a higher CBR (translates to better quality) for 70 min. or less and CBR for anything higher.
If you really wanted to use VBR, the bitrate calc I referred to earlier gives me 9,000,000 / 8,184,000 / 4,088,000 for a 70 min. video.
Following my “never exceed 8,000,000” rule, the VBR becomes 8,000,000 / 8,000,000 / 4,088,000.
Either way, my CBR & VBR values are much higher than the Sony defaults which will mean a higher quality image.

p.s. The Sony default numbers should be good for up to a 1 hr. 35 min. video.
At that program length, my bitrate calc gives me a CBR of 9,608,000 / 5,976,000 / 3,584,000.
The higher Min. value will still result in a higher quality image than the Sony defaults.

It comes down to a personal choice as to whether to go with the defaults or not and I prefer not to.

[Michael Spooner]

Thanks for the further input.

While I’ve got you guys, I had another question regarding frame rate:

Is it possible to author 30p video to DVD and have it be compliant with the DVD specification? From what I’ve read, I get the impression that 24p is the only progressive standard that DVD will accept. Sony Vegas, for example, only has templates for 24p and interlaced at 30fps (60i). That being said, I burned a test DVD in DVD Architect with 24p, 60i, and 30p versions of my video, and it didn’t give me any trouble. When played back on my progressive scan TV, the 30p version is far and away the best of the three. There are NO interlacing artifacts, whereas the 60i still has some, and the motion is much smoother than 24p since there is no pulldown. When played back on a computer screen, there is absolutely no comparison between the 30p and 60i. 30p wins hands down.

My project is all still images with panning, zooming, etc done within Vegas so I can change the output frame rate and interlacing at will without concern over how the video was captured.

Disc space is not an issue, and I would like to get the best possible quality within the DVD spec. I like the progressive scan of 24p, but prefer the higher framerate of the standard 60i. Is 30p an option, or do some DVD players have trouble decoding it?

[James Redmond]

Mike what I was really asking is that you use the constant bit rather than the variable?

Thanks again Mike.

James Redmond
Dynamic Videos, Inc.
Rogers, AR USA

[Michael Spooner]

I think he may have typed “CBR” in a few spots he meant “VBR”..?

[Mike Kujbida]

Good catch Michael.
Now I’m embarrassed and it’s to late to edit it 🙂

In my previous post I said
As I said, I use a higher CBR (translates to better quality) for 70 min. or less and CBR for anything higher.
and
At that program length, my bitrate calc gives me a CBR of 9,608,000 / 5,976,000 / 3,584,000.

What I meant to say was
As I said, I use a higher CBR (translates to better quality) for 70 min. or less and VBR for anything higher.
and
At that program length, my bitrate calc gives me a VBR of 9,608,000 / 5,976,000 / 3,584,000.

[Michael Spooner]

Thanks for that. Now I’ve got another sound-related question… Is there an advantage to coding AC3 in Vegas (at render) rather than importing wave files into DVD Architect and letting Architect convert them to AC3?

Some of my sound files are coming from Cakewalk Sonar and not going through Vegas at all, so I’d rather just convert them as the last step in Architect.