To MPEG or DEFAULT Quantize Matrix, that is the question?

[heavydan]

Hello all.

After browsing through the posts, I see some people say use MPEG setting for Quantize Matrix, and some people say use DEFAULT.

I thought I would read about how quantize matrix is made up and works so I could make my own decision, but I couldn't understand the formulas, etc.

Can someone please explain why the MPEG or DEFAULT quantize matrix settings are better or worse than the other?

Thankyou.

[heavydan]

Briefly speaking, a trap that newbies seem to fall into is that we want the best picture quality. By adjusting bitrate/resolution/gop structure/VBV Buffer/etc.

But in doing so we may actually be creating our own new problems. One cause is that we stretch the bitrate needs of each picture frame beyond the ratio of bitrate available.

If this is correct then the idea must be not to stray to far from the VCD standards, and if you do adjust them then you should scale all settings up respectively.

I am slowing understanding each of the different settings but I don't understand enough about the quantize matrix to know how best to use or modify it.

My question is will the difference between Quantize Matrix settings of DEFAULT or MPEG create blocks/color difference/modify motion/free up more bitrate/ or what exactly are the differences??

Thank-you

<font size=-1>[ This Message was edited by: heavydan on 2001-12-19 14:15:10 ]</font>

[heavydan]

Just modified my question above, to see if anyone will answer. :->

[KoalaBear]

Essentially, quantization is the method by which MPEG achieves bitrate control. The greater the quantization factor (Q), the more picture data gets thrown away to achieve the specified bitrate.

Multi-pass encoders optimize the quantization table on the fly to adjust the degree of compression according to the properties of the input file. The process is entirely automatic -- you set the min/avg/max bitrate and the encoder handles the rest.

This topic has been covered before; do a search to reveal threads that discuss the concept in more detail.