3ivx MPEG Quantization questions

[SeeMoreDigital]

I've been playing with 3ivX's encoder and the other day generated some encodes using the MPEG Quantizer

According to bonds excellent Mpeg4 Information Guide, MPEG Quantization is described as follows: -

MPEG/Custom Quantization:
While with MPEG-4 Simple Profile you can only use the h.263 quantization type, the ASP also allows you to use custom ones
While the h.263 type will bring you a softer image (good for 1CD encodes), the default MPEG matrix is better for higher bitrates, preserving more details
a popular custom matrix is for example hvs_good, also nice for lower bitrates, but there are also many more

What matrices does 3ivx use and does it work better when used with Adaptive Quantization?

Also, is it worth discussing this topic now or better to wait until the new 3ivx release, should things change?


Cheers

[Stux]

"MPEG Quantization" in 3ivx implies use of the default MPEG quantization matrix, which tends to produce a sharper result with more noise preservation and a tendancy to block at low bpp encoding

The next version of 3ivx can use Custom Quantization as well :)

[RadicalEd]

What is the default matrix, just out of curiosity? :|
XviD's standard matrix is different from the 'MPEG' matrix present in all the QM packs I've seen, so.. I wonder which is correct.

[bond]

Originally posted by RadicalEd
What is the default matrix, just out of curiosity? :|
XviD's standard matrix is different from the 'MPEG' matrix present in all the QM packs I've seen, so.. I wonder which is correct. i dont really know the answer so i can only guess that there is a difference between the default mpeg-2 matrix compared to the default mpeg-4 one, and all these packs label the default mpeg-2 one as "mpeg"

[SeeMoreDigital]

Originally posted by bond
i dont really know the answer so i can only guess that there is a difference between the default mpeg-2 matrix compared to the default mpeg-4 one, and all these packs label the default mpeg-2 one as "mpeg" Well, whatever the matrix is.. it's actually quite good :)


Cheers

[Stux]

Originally posted by SeeMoreDigital
Well, whatever the matrix is.. it's actually quite good :)


Cheers

The MPEG-4 video specs specify a "default" mpeg quantization matrix which is hard coded into the decoder. Essentially this is the matrix used when no custom matrix is specified.


INTRA

8, 17, 18, 19, 21, 23, 25, 27,
17, 18, 19, 21, 23, 25, 27, 28,
20, 21, 22, 23, 24, 26, 28, 30,
21, 22, 23, 24, 26, 28, 30, 32, /* w3515 3.4.5.1.2 */
22, 23, 24, 26, 28, 30, 32, 35,
23, 24, 26, 28, 30, 32, 35, 38,
25, 26, 28, 30, 32, 35, 38, 41,
27, 28, 30, 32, 35, 38, 41, 45

INTER
16, 17, 18, 19, 20, 21, 22, 23,
17, 18, 19, 20, 21, 22, 23, 24,
18, 19, 20, 21, 22, 23, 24, 25,
19, 20, 21, 22, 23, 24, 26, 27,
20, 21, 22, 23, 25, 26, 27, 28, /* w3515 3.4.5.2 */
21, 22, 23, 24, 26, 27, 28, 30,
22, 23, 24, 26, 27, 28, 30, 31,
23, 24, 25, 27, 28, 30, 31, 33


Its a very well balanced matrix ;)

[SeeMoreDigital]

Originally posted by Stux
The MPEG-4 video specs specify a "default" mpeg quantization matrix which is hard coded into the decoder. Essentially this is the matrix used when no custom matrix is specified. Thanks Stux

But correct me if I'm wrong... but you can't specify custom matrices in 3ivx... can you?


Cheers

[RadicalEd]

Originally posted by SeeMoreDigital
But correct me if I'm wrong... but you can't specify custom matrices in 3ivx... can you?
Originally posted by Stux
The next version of 3ivx can use Custom Quantization as well :)


Thanks for the matrix, btw.
Somewhat off topic, but on the subject of the next 3ivX incarnation, would it be possible in the muxer to include an option to set the sbr tag for raw aac input? >.>

[Stux]

Basically, our position on that is that aac should never not be in MP4, ergo, there is no problem to be fixed.

If a user chooses to screw up their MP4 aac files by extracting the stream to raw AAC, that's their problem and we won't muddy up our gui to fix it and at the same time providing a way for people to screw up their LC-AAC files by modifying the AudioConfig data to specify HE-AAC.