How to capture with variable bitrate?

[virtual133]

I was wondering if there are any programs that capture with variable bitrate - so I can fit 2 hrs on a DVD and still have good quality.

If you guys have any suggestions on how to get 2 hrs on 1 DVD let me know! Thanx.

[redwudz]

I'm not aware of a capture program that could adjust bitrate on the fly as it captures. It takes a lot of CPU power just to capture. If you also had to scan the video at the same time for scene changes, brightness, etc...? After you have captured, to get 2 hours at good quality just takes knowledge of how your encoding program works and how to adjust it for best results. A lot depends on your video source. A DVD with high quality video is easier to 'shrink' down and still retain quality. A lower quality like off the air TV would take a lot more work to retain quality. You should spend some time reading the guides, especially the ones that relate to the encoder you are using for getting the best quality.

[ronnylov]

If you have an ATI capture card you can set it to capture VBR, average and maximum bitrate with ATI multimedia center. I think you can do the same thing if you capture with Mainconcept encoder.

The capturing encoder will do something similar as a standalone encoder does when making one pass VBR encodings. The quality depends on your input signal quality. If you capture a letterboxed movie then there's no problems to fit 2 hours on a DVD with acceptable quality and 704x576 PAL resolution (but you need a powerful PC to capture directly to mpeg2 at this reolution). If you capture sports or home movies you can still get good quality but maybe then you can try half D1 resolution like 352x576 PAL.

Another alternative is to capture to low compressed avi (huffyuv or mjpeg codec) and the use a standalone encoder to make a 2-pass VBR encoding after completed capturing. If your source is noisy it may help with some filtering also.

[ajc53]

If you are asking about going directly to MPEG 2 with your ADVC -100, MainConcept PVR is going to be your best bet, since you are dealing with DV. You can download a trial version and test a few minutes to get a idea what it will do.

As far as how much time you can squeeze on a DVD, there are tons of information on this site. Search "resolution", as there is a recent thread which covers it well.

You will find that a half DVD resolution of 352 x 480 with around 4,000 bit rate is about what you will need, whether you do it while capturing (transferring in your case), or encoding it later.

No mater what you do, there is going to be a nice little learning curve.

[Capmaster]

Capture full DVD resolution, use "VBR", and set your average to about 4700 Kbps and set the peak to about 6000. That should get you 2 hours with decent quality.

Bitrate calculators are really only useful for CBR, or constant bitrate. VBR is dependent on the amount of motion and other factors in the material you're capturing. Results will vary.

[SaSi]

Bitrate calculators are really only useful for CBR, or constant bitrate. VBR is dependent on the amount of motion and other factors in the material you're capturing. Results will vary.

I think I will disagree. Using a bitrate calculator, for CBR you use the selected bitrate and for VBR you will use the Average bitrate. The calculation results should be correct in both cases.

Regarding the capture subject, I would also use MainConcept, but not in VBR mode but Constant Quality mode. To be able to select Constant quality, you enter 0 to min/max/avg bitrate and the Constant Quality selector get's enabled. Min quality is 31, max quality is 1. This will ensure a constant quality in the capture with an average bitrate that cannot be determined before the capture is complete.

[Paul Simmel]

Another solution, and one I am using right now, is to encode normally with qaulity in mind. Then use DVD Shrink or some such to finalize the project. I am putting 5, 28 minute clips on each DVD with excellent results. There's an active thread on DVD Shrink's Quality right now. Some might argue that my suggestion is adding a redundant step to your project, and I wouldn't disagree. But there are no miscalculations and everything runs smooth with no surprises, with great results.

[Capmaster]

I think I will disagree

OK.

After the first few times I followed the bitrate calculator and ended up 50 or 100MB over the DVD size limit I decided I'd make up my own chart of time vs. bitrate. But, hey, that's how we learn.

After over 2,000 movies captured I think my chart is based on real-world results.