VBR/CBR Help Needed

[greenstrat]

first off, I'm usinge DVD Lab to author and it's great. I'm encoding MPEG's via Adobe's internal mainconcept encoder, no complaints. I do a lot of sports and was told to use a high VBR. Adobe has Low/Med/High bitrate defaults for VBR encoding. My projects never run over 1hr (I'll just use more disks instead of sacrificing quality. What is the relationship between VBR and file size. Does a high VBR use more frames or less when it encodes, is there no diff in file size? What would happen if I used CBR?? I want the best possible pic, the smoothest video as possible, I want don't want a WR running a deep out to look like an Atari 2600 character. For max quality, what are my best option(s). I've come a long way and am now focusing on the little things to produce as high a quality as I can.-sg

[cdcox]

I'm no expert but I'll give you my 2 cents and what I do. I do alot of home movies, b-day ect. I normally use a cbr at a high rate if my video runs less than 90 min, I will give you a constant quality. I use vbr when my video is running longer 2 hrs or so and there is alot of action, ie kids jumping around or a cedar point video with kids on rides. The vbr will use the max kbs you set when it sees more movement and will drop down to the low kbs setting when less movement is there. I personally use Tmpgenc + and a bitrate calulator to get an idea of what I want to set my bitrate at. Hope this helps

[rghogue]

I've got a 40 minute production I did which includes lots of movement with kids running, jumping, etc. I've been trying to put the project on DVD. I've encoded it with TMPGEnc set at a CBR of 8000, with uncompressed audio. I used Ulead Movie Factory 2 to author and burn it. When I tried to play the disc in my DVD player, it ran the menu fine, then when the video faded in, it froze the player.
I encoded again, but with compressed audio. This newer disc works in the player, except that during a part where there's black background with white text, or a fade to and from black, it stutters (audio, too) until it gets to full video, then it runs smoothly.
I checked it in my computer and it plays fine.
I checked it in a friend's DVD player and it played fine.
BUT, in his Playstation 2, it stutters some during the black background with white text, and when fading up from black, it freezes briefly, then runs smoothly.
Since, you said you encode with TMPGEnc at a high bitrate, I'm wondering if you ever had this problem before? Do you have any ideas for me on this?

[greenstrat]

8,000 is crossing the threshold for most set-top players, keep it down under 7,000 and you should be ok. Your friends player probably has more processing power (maybe a higher end or more recent model??) and simply handles a heft bit rate much better. Keep in mind, if your audience is only you, you're fine, otherwise try to keep the bitrates under 7,000.-sg

[SaSi]

CBR encoding at 7~7500kbps will certainly give excellent results. So if you only want to store an hour's worth of material, VBR is not really worth looking at.

VBR is really worth when encoding lengthy content that can't reasonably be cut in separate disks. It's a compromise that when used correctly, will give extra space without compromising quality. But there you need a clever and good encoder to achieve this.

VBR is not using less or more frames than CBR. If you are encoding PAL, then the encoder is doing 25 pictures per second constantly, because it must. VBR just compresses some of the pictures more than it does others. It does so when motion is low and the change between the pictures is "considered" to be small. This is an encoder's decision, and that's why you need to use a "clever" one to achieve good results.

Sports material typically is high action with little "idle" scenes. So, it will typically "suffer" when bitrate goes under 5000kbps.

On the other hand, CCE is an encoder that can achieve miracles even at low bitrates. Using it in 3-4 passes with the ultra-low bitrate Quantization matrices it can do a 200/3800/7500 VBR encoding with astounding quality. The trick is that it uses the QM correctly and the encoder is able to correctly change the bitrate. Also, it slightly softens the image when bitrate is running out - rather than generating blockiness.

The MPEG encoder Adobe uses is the Mainconcept one. It's a good one, but not in the same league as CCE. In it's current version it's not particularly good at VBR, so you are better off with CBR at 6000kbps or more (for sports).