Low Bitrate: Do you Low Bitrate all or Low Bitrate select?

[JFerguson]

Hey all. I was looking at a couple of .ECL files from a couple of PREPARE runs against a low bitrate project (2987kbps) - Pulp Fiction CE R1, using CCE.

I was wondering how you guys configure your project under these conditions? It looks likes you can go:

Main Feature Matrix = Encode Default
Low Bitrate Matrix (< 3Mbs) = Low Bitrate

in which only the segments that are low bitrate will have the matrix applied, or

Main Feature Matrix = Low Bitrate

in which all segments will have the matrix applied. In this project, it looks like about half the segments would get the matrix applied if using the first option and I'm kind of wondering if that would yield an inconsistent encode??

Thanks...

[TheSeeker]

Hey all. I was looking at a couple of .ECL files from a couple of PREPARE runs against a low bitrate project (2987kbps) - Pulp Fiction CE R1, using CCE.

I was wondering how you guys configure your project under these conditions? It looks likes you can go:

Main Feature Matrix = Encode Default
Low Bitrate Matrix (< 3Mbs) = Low Bitrate

in which only the segments that are low bitrate will have the matrix applied, or

Main Feature Matrix = Low Bitrate

in which all segments will have the matrix applied. In this project, it looks like about half the segments would get the matrix applied if using the first option and I'm kind of wondering if that would yield an inconsistent encode??

Thanks...


I use encoder default for first two options under matrices (main feature, and low bitrate). THen for very low bitrate < 2mb and for extras matrices, I use Bach1. Seems to work wonders. That way for the segments that are higher bitrate you dont have some low bitrate matrice being applied and possibly degrading the quality more than is necessary.

I guess this begs the question: For low bitrate situations < 3MB is there a decent matrice? I know bach1 is made for like < 2 MB but is there anything for slightly higher bitrates?

[archaeo]

this has always confused me a little - if you choose 'encoder default' for the 'main feature', does this mean it uses only one matrix for the entire main feature, or does it apply whatever is needed to meet the bitrate demand?

[Fishman0919]

this has always confused me a little - if you choose 'encoder default' for the 'main feature', does this mean it uses only one matrix for the entire main feature, or does it apply whatever is needed to meet the bitrate demand?

Encoder Default is whatever the deafult matrix is for that encoder (most uses MPEG Standard) and is used for every segment in the main movie

Edit - unless Low Bitrate Matrix (< 3Mbs) is used then any segment under 3000k will use whatever matrix is pick for that.

[archaeo]

Encoder Default is whatever the deafult matrix is for that encoder (most uses MPEG Standard) and is used for every segment in the main movie

Edit - unless Low Bitrate Matrix (< 3Mbs) is used then any segment under 3000k will use whatever matrix is pick for that.


OK, so if I understand this right - even if I pick default matrix for the main feature, if the encoder hits a low bitrate segment in the main feature, it kicks into the 'low bitrate' matrix selection for that one particular segment?

furthermore...
Does enabling CCE's 'Adaptive Quantizer Matrix' feature (AQME=1) affect these pre chosen matrice settings in RB in any way? Does one overrule the other?

Thanks for the response (and the question).

[Fishman0919]

OK, so if I understand this right - even if I pick default matrix for the main feature, if the encoder hits a low bitrate segment in the main feature, it kicks into the 'low bitrate' matrix selection for that one particular segment?

No, only if you choose in "Low Bitrate Matrix (< 3Mbs)" a diff matrix from "Encoder Default" or in "Very Low Bitrate Matrix (< 2Mbs)"..... with these settings you can have the encoder use a diff matrix if the avg bitrate of a segment being encodes goes below 3000k or 2000k..... and you can have the encoder use a diff matrix for extra's also..... if you leave in Low Bitrate Matrix (< 3Mbs),Very Low Bitrate Matrix (< 2Mbs) and Matrix for Extras to Encoder Default then whatever you pick for Main Feature Matrix will be used for everything

Does enabling CCE's 'Adaptive Quantizer Matrix' feature (AQME=1) affect these pre chosen matrice settings in RB in any way? Does one overrule the other?

Yes, only if the lowest quantization scale cannot raise the bitrate under a single quantization matrix..... from the CCE SP guide...

What is adaptive Q-matrix switching ?
There are some cases that Cinema Craft Encoder SP cannot keep
the minimum bitrate. It is considered to be caused by that the lowest
quantization scale cannot raise the bitrate under a single quantization
matrix. To solve the problem, Cinema Craft Encoder SP automatically
creates other matrices cutting the value of each element in the
matrices by half, quarter and so on, and applies another one to produce
a much lower distortion for much higher bitrate. This switching
of quantization matrix can occur at every GOP.
Thus, adaptive Q-matrix switching can improve the quality of image,
especially with lower bitrate sources or CG works or the edge of
fading out.

So with adaptive Q-matrix switching on low biterate can be improved.

[archaeo]

fishman, thanks
yeah that's what I meant in my first statement...if you have chosen a different matrix for 'low bitrate' than what is chosen for the main feature, than it will kick in as needed if it encounters a low bitrate segment.

As for AQME, I tend to think it is just good practice to use it, as I do, to allow CCE to adjust itself as necessary to meet low or high bitrate demand... It seems to offer the most adaptability during an encode. But I have read that there could be some problems with some players. I havent had any yet, so far.