TMPGenc encoding - CBR or VRB?

[Will Hay]

Could someone please explain the difference between the dvd encoding templates within TMPGEnc for CBR and VBR?
Should I be using one over the other to encode from CladDVD and DVD2AVI?
Thanks,
Will

[wulf109]

A retail DVD disk is encoded as VBR not CBR. That's the best reason I can think of for using VBR mode.

[MpegEncoder]

wulf109,

I sort of agree with you. But I think that you have it backwards. The reason that DVDs use VBR is because it makes the best use of space and that's the reason to use it (VBR). So the best reason to use VBR is not because DVDs use it, but because it saves space. If space is not important CBR is fine.

[puertorican138]

Constant Bit Rate(CBR): This means that your bitrate will have a fixed setting, and during high motion scenes, due to being fixed, block noise may occur. It is encoded by TMPGEnc reading a few frames and then encoding them. More or less it thinks about what it is going to do before it does it.

2pass Variable Bitrate(VBR): This means that your bitrate has an minimum, maximum, and average bitrate. On this one you can set the average to a fixed setting and have it either raise to the maximum you set during high motion scenes or fall to the minimum you set when there is little motion. This setting is good for figuring out the size of the file that is being outputted and to have it reach higher bitrates yet still maintaining a lower file size. under the settings of this setting is where
you would put in everything you need to. There is also a setting, "Enable padding When falling below the minimum bitrate", if checked. forces the rate of the movie not to fall under the minimum bitrate you entered. Also this setting will go over the whole movie first then at 50% it will start to encode it, and this takes time...Allot of time! Why would anyone do this you ask. Well I do this because I know approx. what the file size will be and I feel that I will get the most out of my movie. This is for MPEG-2 (SVCD), DVD, or Non-Standard MPEG-1 (XVCD).


Hope That Helps!!! :P

[puertorican138]

Since you source is from a DVD, I would recommend using VBR as it can give you a predictable filesize with excellent results. Also, make sure your player can play XVCD's.


Hope That Helps!!! :P

[MpegEncoder]

Constant Bit Rate(CBR): This means that your bitrate will have a fixed setting, and during high motion scenes, due to being fixed, block noise may occur. It is encoded by TMPGEnc reading a few frames and then encoding them. More or less it thinks about what it is going to do before it does it.

This is not correct. Block noise does NOT occur due to being a fixed bitrate. It is due to insufficient bitrate to handle the motion. This can occur just as easily for VBR as CBR. If you encode a file using CBR @ 2520Kbps and a VRB @ 2520Kbps max, the CBR will always be better. It will also take LOTS more space.

[graysky]

Space is the major reason. Why use tons of bits when they are not needed? Same reason VBR mp3 files are superior to CBR mp3 files...

[mikeweb]

So what min bitrate should someone set?

[puertorican138]

Set your Minimum Bitrate to 300 or 500 (to be safe) because some players can't handle really low bitrates. Thanks for correcting me, MpegEncoder!

Hope That Helps!!! :P

[mikeweb]

So a lower min bitrate is better then a higher one? or is it the other way around?

[MpegEncoder]

So a lower min bitrate is better then a higher one? or is it the other way around?

Higher bit rates give better quality, but they take more space. The "low (minimun) rate" for VBR is used during portions of the video that don't have much motion.

[vitualis]

Assuming that the MPEG encoder isn't broken, a lower minimum bitrate for a VBR type encoding should yields superior quality. This is as it gives the largest bitrate flexibility to the MPEG encoder. Optimally, the minimum bitrate should be zero.

The minimum bitrate issue generally only refers to S/VCDs (i.e., CD media). I don't believe it is relevant for DVDs as DVDs are always read at a constant rate (the maximum rate in fact) and don't spin down for low bitrate sections. However, if anyone knows better, please post.

Regards.

[jj1k]

Ive been backing up over 50 dvd's now.

I use CBR BUT I change the setting to 10bit and change quality to High in the settings. Movies look great, even a 180min on 1 DVD looks very good.

VBR takes a LONG time, with CBR I set the size to 103% and it always gives me a nice 4.28gb movie

James

[mikeweb]

Assuming that the MPEG encoder isn't broken, a lower minimum bitrate for a VBR type encoding should yields superior quality. This is as it gives the largest bitrate flexibility to the MPEG encoder. Optimally, the minimum bitrate should be zero.

The minimum bitrate issue generally only refers to S/VCDs (i.e., CD media). I don't believe it is relevant for DVDs as DVDs are always read at a constant rate (the maximum rate in fact) and don't spin down for low bitrate sections. However, if anyone knows better, please post.

Regards.

But MpegEncoder said that a higher min bitrate is better then a lower one. So lets say I set these settings, which will have a better looking picture?

A) Min = 1200, Avg = 1900, Max = 2520

B) Min = 200, Avg = 1900, Max = 2520

[vitualis]

I think that he simply phrased it badly. I think he actually meant that a higher average bitrate will lead to better quality (rather than higher min bitrate).

In your example, (B) should have better quality assuming all other things are equal.

Regards.

[MpegEncoder]

That is correct. A lower min rate allows move avg bits. Therefore, increasing quality for those parts of the video that are somewhere in the middle of the bit rate requirements.

[dc91gt]

Assuming that the MPEG encoder isn't broken, a lower minimum bitrate for a VBR type encoding should yields superior quality. This is as it gives the largest bitrate flexibility to the MPEG encoder. Optimally, the minimum bitrate should be zero.

The minimum bitrate issue generally only refers to S/VCDs (i.e., CD media). I don't believe it is relevant for DVDs as DVDs are always read at a constant rate (the maximum rate in fact) and don't spin down for low bitrate sections. However, if anyone knows better, please post.

Regards.

But MpegEncoder said that a higher min bitrate is better then a lower one. So lets say I set these settings, which will have a better looking picture?

A) Min = 1200, Avg = 1900, Max = 2520

B) Min = 200, Avg = 1900, Max = 2520

they would turn out pretty much identical.

-d

[vitualis]

That would depend on the source material.

Hypothetically, as case (B) offers a greater bitrate range for the encoder to work with, it should yield better quality.

Regards.

[mikeweb]

Lets say that the AVG and the MAX are the same (2520) and the MIN is 300. Would that yeild a good picture over lets say what I wrote in example (B)?

[MOVIEGEEK]

Lets say that the AVG and the MAX are the same (2520) and the MIN is 300. Would that yeild a good picture over lets say what I wrote in example (B)?

You might as well choose 2520kbps CBR because the size savings will not justify the extra time to encode.

[SatStorm]

For TMPGenc (not CCE...) my tests show me some interest results, worth sharing...
There is a minimum bitrate needed to support a still picture with this encoder.
This is about 1000kb/s for CVD, 1250 for SVCD and ~2000 for full CCIR DVD.
For VCD this value is about 500kb/s. That was well known to older users, and there was a time that anybody suggested this value for 2 reasons: The first was that many DVD standalones of that time didn't support lower values during the playback. The second reason, is that for the 352 X 288/240 framesize, 500kb/s are neccessary to support well a still picture.
Most users today, know somehow this info, and adapt it as a fact for any CD/DVD media base format, without fully understanding why they do it. Well, bad news, at least with TMPGenc, you have to increase it for other formats beyond VCD if you want better results!

Also, for better pixel allocation, TMPGenc needs in praxis the minimum and maximum bitrate value to be equal distant from the average one.
For example, you make a xCVD with an average 2300kb/s. If you set 1000kb/s for minimum and 3600kb/s for maximum, the quality gonna be far better using min 300, 2300 average and let say 4000maximum.
This is for TMPGenc only, CCE works different from what I know.

If you follow those simply rules, your TMPGenc encoding gonna be fair close CCE's ones. In my eyes, there is no difference, but since I am not a CCE expert to explore and test the CCE's cutting edge abilities, I can only say that at least, the results are close enough.