using 2pass vbr as opposed to automatic vbr : LUSENET : Video CD : One Thread

I am using TMPG INC. to make SVCDs. One of the guides i read mentioned i can use TMPGs automatic VBR or 2pass VBR which takes alot longer but produced much better quality. What is a VBR. And how do i enable/use 2pass vbr?

-- dave bengel (, January 01, 2001


Take a look at my web site that tends to blow that concept away because the data rate of SVCD is so low as not to be any better than CBR. The example used shows quite clearly hat VBR in any form is a misnomer in SVCD and VCD's and is really only useful when you get to data rates above at least 5000 kB/s. Try the same source material and have a good close look at the results. Try the SVCD page and then the DVD page.

-- Ross McL (, January 01, 2001.

Variable Bit Rate(VBR) opposed to Constant Bit Rate(CBR). CBR means that you encode a video stream with a locked data rate, which is called by a particular standard such as VCD compliant. CBR waste a lot of good disk space and also provides poor performance during high motion scenes. VBR provides the means to optimize disk space and performance during low and high motion scenes by giving the encoder the freedom to assign data rate to video scenes appropriately. Therefore, the encoder usually has three variables to work with, a minimum data rate value, an average data rate value, and a maximum data rate value. The minimum and the average values tell the encoder where a low motion scenes data rate should fall, while the average and the maximum works with high motion scenes.

-- lnguyen (, January 01, 2001.


I worked with Auto VBR and the file size grew too large - end VCD Compliant MPEG file.I guess i did not work with the bit rate settings

can u please advice me on what the best settings would be as per your perspective

I am using TMPGENC Automatic VBR (CQ-VBR) Quality : 50 Max Bit Rate : 3000 Min Bit Rate : 6

Enable Padding when falling below min bit rate - Unchecked

The picture qulaity eas too good ut the file size grew very big to double the size that it normally would

Thanx in advance

-- Iyappan (, January 03, 2001.

VCD is supposed to be encoded using CBR @ 1150Kbps in order to be compliant. This is the rule; Nevertheless, you can bend this rule to make it works base on your needs.

The whole idea of using VBR is to optimize quality versus disk space. However, most thing in life are moving quite fast especially action video and this means you need to encode them with higher data rate in order to keep the quality intact. This also means you are using up more disk space for them (This is why VCD limitation is set to 1150Kbps). Nevertheless, most action video also contains slow moving scenes as well, but you don't really want to encode them with higher data rate either. That's why you do VBR. you can save some of your disk space from these scene. Unfortunately, the ratio of high motion versus low motion scenes are not equally divided, so you will not be able to achieve an average of 1min per 10Mb like VCD! The best you can hope for is an average of 16Mb per minute. This also means you can only fit about 35 to 50 minutes per CD depending on how much things are moving around on your video stream. You will not get 74 minutes out of this type of encoding scheme.

Set Quality to 65-75(higher means bigger file size). Set min to 600 and max to 2600Kbps(bigger number here also means bigger file 352x240 you really don't need to go beyond this data rate). Use TMPGENc's filters with the above settings to achieve better quality. I'd use noise redution(32-37,1,32-37) and edge enhancement (27-34,22-26). Play with these ranges in the filter to see what is best for your "quality". You can use preview mode in these filters' settings to check.

-- lnguyen (, January 03, 2001.

Hi Long

Going to get on the opposite side of the fence on the question on VBR and CBR in VCD or SVCD encoding.

In theory I understand and agree what you say but in practice consider this case for disagreement .....

Please take the trouble to look and study the following bit rate graph from my web site:

The DVD compliant file is almost at full rate and is a VBR which is truly useful. The SVCD graphs comparison, and if you consider VCD would be in the 1000 area, bears no relationship AT ALL to the full rate DVD file, indeed it indicates there is no advantage in using VBR. If there are no troughs in the main file as low as 2600kB/s then you will never get the VBR effect in the encode. I will bet if I were to take the derive average of the VBR file and encode it at CBR you would never see the difference. The reason that people think VBR better is that the average is lower and that when you have a DVD player not capable of playing the higher data rate it appears that way. My Philips 725 is in that catagory it can play a VBR file set for 2500, BECAUSE THE AVERAGE DATA RATE IS down near 2300 and if one encoded CBR at 2300 you will never know the difference, thats why I set 2376 or more recently 2350 for CBR.

Sorry my friend, if I am wrong then please explain how you see VBR as being effective as presented in those comparison files.

I have several DVD compliant files ready for "DVD by Remote" and all are VBR encodes. I can tell you now, apart from where stills are in the video, the achieved data rate is consistantly between 8000 and 9000 just like the CBR encode produces, but spending money to get then done by remote means I stick with VBR. Afterall, as far as a DVD player is concerned, to meet the spec, it must play a continuous 9800kB/s and that is a CBR capability.

The graph below clearly illustrates what I am talking about, it is the continuation of the one mentioned above and as you can see the file is using what might be called CBR from the 20 second point on, very little fluctuation. I would love to read a comercial vob file from a DVD. There is no way in .... that you will get VBR from that source if only using SVCD with an upper limit of 2600 in the spec.

I rest my case, hahahahaha!

-- Ross McL (, January 04, 2001.

here is another image that demonstrates the discusion:

Its interesting how the SVCD follows the shape at low values as I suggested, but does not towards the end, when the actul data rate is way above that being used. Totally different outcomes in my view which can be produced with CBR as well. Stills presentations should always be CBR to get the best image.

Cheers - I look forward to your "case for" Long.

-- Ross McL (, January 04, 2001.


Please take a look at my data ( I've no web page to post the info so I am sending it to you via email ). Please tell me what I did wrong there. What you've said and presented with the graph are absolutely correct. I have no argument with that information.

-- lnguyen (, January 05, 2001.

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