DVD Encoding - CBR or VBR

[raceman3]

I normally use Ulead Video Studio to edit and encode my videos. However since I aquired the Sony DRU500 DVD burner I've been trying TmpGenc as well as Ulead. There was a good article posted on this web site about tweeking TmpGenc to get the best DVD quality. I have two questions: My Video source is a Sony Digital video camera, am I going to get any better results if I tweek TmpGenc versus using the default NTSC DVD template ? Second, I noticed Ulead defaults to VBR encoding and TmpGenc defaults to CBR encoding, both as NTSC DVD. I understand that the VBR may save some space but am I loosing quality with CBR and what is the actual NTSC DVD standard CBR or VBR ?

[SingSing]

VBR can get as good as CBR ( Sometime actually better ).
The key is VBR make twice as long to encode.

I use VBR, and just start the encoding, before I go to work.
then came home, burn it, watch it.

[bugster]

Yes, use Tmpgenc with 2-pass VBR for best quality, motion search normal or high (I wouldn't bother with highest). Use MAX bitrate 8000, min 2000 and average calculated according to the length of your video. (4000 gives approx 2 hours).

Home Video footage, no matter how captured, is notoriously difficult for an Mpeg encoder to handle due to the large amount of movement between frames caused by the use of handheld cameras. Therfore you may want to keep your video length per disc down and so increase the bitrate.

Also make sure you use an authoring package that will allow mp2 or even AC3 audio and not MyDvd (which I think is often bundled with the Sony drive) which converts your audio to uncompressed PCM. This occupies about 1Gig of space for 90mins of video. This means your data rate would have to be reduced to fit it on the disk. Use something like DVD Workshop or Dazzle DVD complete instead.

W.r.t CBR vs VBR, certainly with Tmpgenc 2-pass VBR is as good as if not better than CBR (when the VBR average is the same as the CBR value) the cost being a doubling in encode time.

Hope this helps

[DigitalGreg]

I'm still trying to figure out: After using tmpeg_enc to convert the video, what "Make Disc" settings should you use in DVD Workshop? My guess is it doesn't matter as long as you check "Do not convert compliant file", but no one seems to have an answer (and you can forget getting support from Ulead).

[Crystal Symo]

VBR always give better quality than CBR. If you don't want to waste time with 2 pass VBR, you should use CQ, set the Min and Max Bitrate and also the Quality. If you are using DVD bitrates (so high bitrates) you will get very nice quality, surely better then CBR in many scenes. Using this way you can't know the exact size of video file.

If you want the best quality, you should use 2 pass VBR and Highest quality motion processing (very long time for encoding, but max quality as possible).

[epo]

Ulead settings really do not matter. And VBR is much better than CBR of same size.

[energy80s]

VBR always give better quality than CBR.

This is wrong. CBR gives you the best quality. However it does this by using the maximum bitrate all the time. This can be overkill for some scenes (especially at DVD bitrates). You will find that if you use VBR or CQ encoding you will be able to get more "bang per buck" onto your DVDR discs as the file sizes will be smaller, whilst the quality will be maintained. If you are using TMPGenc use CQ, if its CCE then use VBR.

[ItsMe]

Lets reword this.

VBR is *usually* better quality when the average bitrate is the same as a CBR setting.

Some scenes don't really improve by giving them a high bitrate whereas other scenes (cloudy sky, trees, lots of movement etc) may need a very high bitrate. This means that to achieve the same quality when using CBR as a VBR stream you need to set the CBR bitrate as high as the maximum bitrate of the VBR stream thus wasting bandwidth on scenes that don't need the higher bitrate. This wasted bandwith can be used for complex scenes in VBR allowing the bitrate to go right up to 9.8 Mbit/sec if need be.

[energy80s]

Exactly!

[miketree]

So what's the difference between cq and vbr?

[ItsMe]

CQ is a tmpenc thing which tries to keep the quality of the stream constant at a given bitrate. I do not know how the algorithm actually does this.

The way I see it is this

If using CBR with a low(ish) bitrate and with the CQ setting then you will probably get CC (Constant Crap). Using CQ with a high bitrate then you will get a higher constant quality at the expense of a larger file.

On the other hand if you use VBR with a low(ish) minimum and average bitrate and a nice high maximum bitrate then you should get a pretty constant high quality.

[bacardi/avt]

Why not just use CCE? This gives the best quality every time with VBR.

I always use it to encode my DVDs. I just follow the guides at www.doom9.org

[ItsMe]

raceman3: I recommend you encode something twice. Once with CBR and once with VBR and see the difference for yourself using the same bitrate for the VBR average as you use for the CBR bitrate.

[ItsMe]

Why not just use CCE? This gives the best quality every time with VBR.

I always use it to encode my DVDs. I just follow the guides at www.doom9.org

Now thats a good idea, superb encoder. Have you seen the price of CCE though?

[miketree]

can CCE specify the output resolution, like tmpgenc?

[bugster]

CQ is a tmpenc thing which tries to keep the quality of the stream constant at a given bitrate. I do not know how the algorithm actually does this.

Not quite accurate. CQ does attempt to keep a given quality but only within a MAX bitrate (and it sometimes even exceeds this). It is a form of one pass VBR.

[ItsMe]

can CCE specify the output resolution, like tmpgenc?

Yes, Max. 720 x 576.

see: http://www.cinemacraft.com/eng/ccesp.html#soft

[ItsMe]

CQ is a tmpenc thing which tries to keep the quality of the stream constant at a given bitrate. I do not know how the algorithm actually does this.

Not quite accurate. CQ does attempt to keep a given quality but only within a MAX bitrate (and it sometimes even exceeds this). It is a form of one pass VBR.

I stand corrected.

I would like to see a CBR stream that is actually 100% constant. I usually encode using hardware and have the ability to monitor the current bitrate in real time. Even when encoding VCD streams the bitrate varies slightly.

[bugster]

I would like to see a CBR stream that is actually 100% constant

I know what you mean but as far as I understand things, I believe that CBR actually means that the average bitrate per GOP is constant, not per frame. Though I would be gladly corrected if this were not correct!

[snowmoon]

Yes, CBR is based on GOP not frames, obviously the I frame is going to be bigger than a B frame.

Constant quality modes do an excellent job ( CQ in TMPGenc and One Pass VBR in CCE ) of encoding without wasting bits. In TMPGenc the closer to 100 you get the more of the source is preserved, in CCE the lower your Q value is the better. Obviously the higher the quality setting the larger the file. In CCE I can get moderatly clean TV caps down to an average of between 2-3mbps no problem.

To say that CBR is the only way to go is ignorant of the way that mpeg works. A VBR encode with a high quality setting will produce a file that should be indistinguishable, but smaller. You get to decide how small.

I recommend that you try for yourself and see. I would also recommend getting the hang of avisynth for video cleanup. Their are many great filters that can help improve the compressability of a clip without much if any softening.