little question

[canete]

hello jdobss i have a little question:

the parameter CQ defines the quality of the film?
CQ more big, the flim more quality?

[jdobbs]

Not necessarily. It depends what setting you use. If you use a CQ value that is high, your output coud look terrible.

As a rule, for the same size output you'll usually have a little better picture with two pass. But it depends on a lot of factors -- for example, if bitrate is sufficiently high you may not be able to tell the difference.

[canete]

well… when I tell CQ I refer Redistributing Final_CQ.
Down i paste 3 log of the same film with different QC, first is not mine, the second and the third are mine.

In both cases 64 IDCT use = bit IEEE -1180 reference but in 2 case i use like Matrix "AVAMAT 7" and in the third "Decoder default".

My question now is, the three cases have the same bitrate redistribution, the same overall bitrate, but but direfent QC.
What film has more quality? the first??Because his QC is more hig?
In case as I can get this factor of QC?


- AVISYNTH 2.5.8.0
- Rhozet Carbon Coder:
- Mastering Quality (Slowest)
- Half-D1/Half Space for Extras mode is enabled.
- Steal Space from Extras" mode (50%) is enabled.
- Reduction Level for DVD-5: 60,0%
- Overall Bitrate : 3 364Kbs
- Space for Video : 3 671 218KB
- Analyzing VTS_01 for optimal CQ factor.
-- TargetSize (sectors):1 574 237
- Redistributing Final_CQ: 3,8
- Movie improvement from extra reduction = 14,0%
- HIGH/LOW/TYPICAL Bitrates: 8 104/609/3 364 Kbs

-----------------

- AVISYNTH 2.5.8.0
- Rhozet Carbon Coder:
- Mastering Quality (Slowest)
- Reduction Level for DVD-5: 60,0%
- Overall Bitrate : 3.364Kbs
- Space for Video : 3.671.356KB
- Analyzing VTS_01 for optimal CQ factor.
-- TargetSize (sectors):1.574.296
-- Sampling 1764 of 175494 frames.
-- Predicted size (sectors) at CQ=4,0: 1.225.447
-- Predicted size (sectors) at CQ=3,3: 1.375.017
-- Predicted size (sectors) at CQ=3,0: 1.439.266
-- Predicted size (sectors) at CQ=2,8: 1.523.546
-- Predicted size (sectors) at CQ=2,7: 1.522.507
-- Predicted size (sectors) at CQ=2,6: 1.636.870
- CQ Value selected: 2,8
- Redistributing Final_CQ: 2,8
- Movie improvement from extra reduction = 14,0%
- HIGH/LOW/TYPICAL Bitrates: 8.104/609/3.364 Kbs

-----------------

- Reduction Level for DVD-5: 60,0%
- Overall Bitrate : 3.364Kbs
- Space for Video : 3.671.356KB
- Analyzing VTS_01 for optimal CQ factor.
-- TargetSize (sectors):1.574.296
-- Sampling 1764 of 175494 frames.
-- Predicted size (sectors) at CQ=4,0: 1.484.875
-- Predicted size (sectors) at CQ=3,8: 1.559.405
-- Predicted size (sectors) at CQ=3,7: 1.570.731
- CQ Value selected: 3,7
- Redistributing Final_CQ: 3,7
- Movie improvement from extra reduction = 14,0%
- HIGH/LOW/TYPICAL Bitrates: 8.104/609/3.364 Kbs

-----------------

[jdobbs]

Unfortunately there isn't a definitive answer. With all other things being equal a lower CQ indicates a better picture. But -- when they aren't (such as when you change the matrices) it can become dependent upon the characteristics of the source you are encoding. There are trade-offs. One matrix may look better in one type of scene (such as high action) while another might look better in still scenes. One matrix may show more detail with higher pixelation while another shows less with more smoothing. One may be better with stark contrasts (like animation) while another looks better with natural sources.

I wish I could give a better answer -- but the number of variables involved is just immense.