The VBV buffer size does not for the millionth time have any effect on image quality whatsoever, but may give problems on a less than compatible DVD player.
Reason: The VBV buffer is to set the internal buffer size of the decoder.

Basically what happens is there is a space in a memory chip called the buffer which is sort of a like a small pipe (so to call it). This pipe needs to be filled with data from one side before the data comes out on the other. The size of the VBV buffer setting in TMPG determines the size of this pipe.
If the pipe is too big and the data being supplied to it is slow moving such as low bitrate VCD's then what will happen is the pipe (buffer) will not fill quick enough from the input side before the data is requested at the output side causing 'Buffer underflow'

When the decoder requests the video data at the output side then this data won't be there yet so your decoder has no information to supply to the DVD player to put on your screen. To compensate your decoder will just have to wait for the data to appear which will then look like jerky playback because it is always waiting for the data to catch up or your player will just freeze after a certain length of time and refuse to play the movie any further.

A similar thing would happen if its too small i.e small VBV buffer size and the data being supplied to it is high bitrate (such as DVD) then this information will be pushed into the pipe at a fast rate and the pipe will fill faster due to being smaller.
If the pipe fills up before the decoder is ready to take the data at the other end to be put on the screen by the DVD player then the pipe will begin to overflow (buffer overflow) which will cause the DVD player to have to drop frames to keep up with the data flow or may stop playing altogether.

This is the reason why it doesn't affect the actual picture quality and doesn't reduce macro blocks, but the actual picture stability. Macro blocks are what make up the image of a movie and are hard encoded into the movie and can't be removed, but can be made less evident by other decoding filters which which your DVD player uses.

I posted this because of Technos' constant advice of a 224 VBV buffersize which is to big for a standard VCD and is DVD standard. The MPEG standards state the best setting is 40 for standard VCD and should be plenty. I say standard because if you up the bitrate past about 1800kbps then the buffer size should be increased to about 112 and then past around 3500 increased to 224.

Who do you want to believe? The author of TMPGenc and the knowledge of respected experts or some jumped up school kid with a chip on his shoulder.

I hope you now understand why the buffer size Techno is stating could cause problems in your DVD player when playing VCD's.

ASHY

I get "buffer underflow" quite often and it makes the picture shake back and forth really fast on the tv.does that mean that I need to reduce the size of the buffer? and does "packet" size have to do with the buffer size,cuz with other programs (cce)you can"t adjust the buffer size but you can adjust the packet size??? This info will be very usefull cuz i get "buffer underflow" all the time,I usually encode vcd at 1700-2200kbs with a buffer of 80 and a packet size of 2024kb......thanx

Sherlock

Ashy has provided the answer to your question in his above post.
The relationship between Data (Packets) and the VBV is clear to see.

CCE should be discussed elsewhere.

I'm not too well up on packet sizes but what I do know is that the packet size depends on the application receiving the MPEG stream and I think is more relevant to transport streams.
Packets are used for timing information and to keep things in sync and 2048 is MPEG standard for program streams which incidently is what DVD's use.
So to answer your question, you don't really need to worry about packet size as the default is correct for your DVD player.

ASHY

Willyiam If you read the above info it says NOTHING about data packets,the two words "data packets" aren"t in there anywere, so how is it clear to see...you seem to have something against me, so can you please let me know what it is so I can rectify it by sending you flowers or a box of candy.....

Thanx Ashy you have been very helpfull...