Bit Rate Question

[Kevin Lewis]

I know there are lots of posts on this but im still trying to wrap my arms around it since most of my projects are never over an hour long. I have lots of old vhs tapes that I converted to mpeg files. Can I fit more than 2hours of this type of footage on a dvd without losing quality? The orignal source quality is not that great to begin with. I am Using Vegas HD and will be exporting to DVDA 5. Thouhgts?

[Phil Lee]

Hi

You can't put anything on DVD as MPEG video without losing quality as it is a lossy compression system. VHS however is very low resolution anyway so you probably wouldn't notice much, however the trouble with VHS is the video is often quite noisy, this is a big challenge for MPEG2 (well for most compression systems), so you may find the quality loss is too big a hit fitting 2 hours worth on a DVD. It also depends on how well the encoder works and what settings you apply, for example is it variable bit rate so it can save some room on easy to compress footage (not that you find much of that with a noisy VHS) to use more on more complicated scenes to keep quality high?

The best thing to do is try it, certainly going over 2 hours per disk (unless you are using dual-layer) is quite heavy compression certainly for something tricky like analogue footage from VHS.

Regards

Phil

[Kevin Lewis]

So when using Vegas HD and DVDA how will I know when I am putting to much video on a disk?

[Randall Leong]

Originally Posted by Kevin Lewis

I know there are lots of posts on this but im still trying to wrap my arms around it since most of my projects are never over an hour long. I have lots of old vhs tapes that I converted to mpeg files. Can I fit more than 2hours of this type of footage on a dvd without losing quality? The orignal source quality is not that great to begin with. I am Using Vegas HD and will be exporting to DVDA 5. Thouhgts?

As Phil stated, you will lose even more quality trying to squeeze even 2 hours of video that's converted from VHS tape, especially those that had been recorded in EP mode (which is inherently extremely noisy to begin with). This is because video noise is much less compressible than pristine video to begin with. Worse, the effective resolution of analog VHS video is at best 330x480 to 350x480 (with tape recorded in SP mode) rather than the 720x480 resolution of original pristine standard-definition digital video.

Originally Posted by Kevin Lewis

So when using Vegas HD and DVDA how will I know when I am putting to much video on a disk?

It depends on both the video bitrate that you choose, the audio format and bitrate that you choose, and whether you are using single-layer (4.7GB) or double-layer (8.5GB) DVD media. To get even two hours of video onto a 4.7GB DVD, you would have to pick a modest video bitrate of around 4.7 Mbps (assuming that you would be converting the audio to 192 Kbps Dolby Digital). No NLE will directly indicate how many minutes or hours of video that can fit onto a given disk.

By the way, given the quality of analog VHS video (and in particular, VHS tape recorded in the EP mode, which delivered 6 hours of video on a T-120 tape), you would want to use a relatively high CBR (not VBR) video bitrate of around 7 to 7.5 Mbps. This would give you around 75 minutes of video on a single 4.7GB DVD (again, assuming 192 Kbps Dolby Digital audio). Using VBR on such noisy analog video content might effectively make VBR CBR.

[Edward Troxel]

I typically try to limit my DVDs to 2 hours. Having said that, it's all related to the bitrate. Use a lower bitrate and you can fit more on the DVD. The question becomes when YOU can notice the difference. So try a standard render which will hold just over an hour, lower the bitrate to what will hold 2 hours and look at that. Now lower it to what would be used for 3 hours and look again. Basically, you can go as low as you want as long as YOU are happy with the results.