CCE & DC component precision setting

[DRP]

Once upon a time I found a webpage that listed the known bitrate points at which CCE changed its DC component precision setting. I really want to find this information again but I can't. Maybe that page has been removed or something. From memory I think it said that CCE uses 8 bit for anything under 5000kbps, 9 bit for 5000 - 8000kbps and 10 bit above 8000kbps.

I can't remember if these were actual automated settings or just recommendations by the authors of CCE. Can anyone help please with what CCE does regarding the DC component precision?

[adam]

That's about right. My manual says that the general rule is to use 8 bit DC for 4mbits and under and 10 bit dc for 8mbits and over. But the auto setting is not based on bitrate its based on quantization and I believe it will adjust DC precision along with the quantization scale.

You are really supposed to take all compressibility aspects of your source into consideration when setting DC precision but ultimately unless you are using low bitrates or very complex footage (forgot your tripod?) than you are going to be using 9 bit DC for most scenes.

My manual says to consult the "mpeg2 guides" for more information but I can't find any on Custom Technologies' website. Their tech documents section is under construction right now so its probably supposed to be there.

[DRP]

That's about right. My manual says that the general rule is to use 8 bit DC for 4mbits and under and 10 bit dc for 8mbits and over. But the auto setting is not based on bitrate its based on quantization and I believe it will adjust DC precision along with the quantization scale.

Could I please trouble you for a cut 'n paste of the actual text from the manual you're referring to here? I've searched every CCE manual I could find and never found anything as specific as what you say here.

Thank you.

[adam]

This is what my 2.5 manual says. Yes its old so take from it what you will but it conforms with what I have read about dc precision in other sources.

In general the optimum settings cannot be determined since changes depend on the details of the picture and movement intensity. For pictures with intensive movement and fine bumps, a low number of bits is appropriate. For smooth pictures with little movement, a higher number of bits is appropriate. A low number of bits may be specified for use at a low bitrate up to 4 Mbps, and a high number of bits may be specified for use at a high bitrate.

When Auto is selected, the precision varies according to quantization scale.

As for the cutoff of when to go from 9 bits to 10, I cannot find this statement in any of the CCE manuals available on the site but I'm positive I've seen it in one of them in the past. Current manuals simply say to use 10 for DVD-Video but I think that's pretty evasive since naturally you wouldn't do that for low bitrate DVD-Video. I'll try to dig up that old manual.

[DRP]

Yeah that's all I could find too. I wish I had saved that webpage with all the recommended settings for CCE I found earlier. It had very specific information about how the authors of CCE wrote the DC precision logic to work.