Dolby Digital Noise Reduction

[Paul Finn]

Are film Dolby Digital sound tracks encoded with the Dolby SR noise reduction process? If so, do the processors - DA20, CP500, CP650 - apply SR decoding to the recovered digital audio tracks? Is it understood that the commonly used " SRD" naming convention means the SR noise reduction process only applies to the analog soundtracks or both the analog and digital tracks on the film?

Thank you, Paul Finn

[Steve Guttag]

The digital tracks have no noise reduction applied...only the analog tracks.

[Randy Stankey]

Couldn’t it be said that Dolby Digital (SRD) IS the noise reduction?

In other words, the process of encoding to Dolby Digital includes noise reduction if and when it is necessary, such that no other noise reduction, outside of what Dolby already does, would be needed.

Or, maybe, I should say that Dolby Digital is the same thing as the old SR except that is done digitally, hence the “D.”

[Ryan Gallagher]

Couldn’t it be said that Dolby Digital (SRD) IS the noise reduction?

In other words, the process of encoding to Dolby Digital includes noise reduction if and when it is necessary, such that no other noise reduction, outside of what Dolby already does, would be needed.

Or, maybe, I should say that Dolby Digital is the same thing as the old SR except that is done digitally, hence the “D.”

I was gonna suggest something along those lines, SR type noise reduction very well may be in the production chain somewhere... just not handled and the processor. Especially perhaps true when remastering things that previously had no Digital on their original release prints. Era wise Dolby Digital probably became available while a lot of films were still recording, mixing, and mastering audio with analog methods.

[Josh Jones]

Are film Dolby Digital sound tracks encoded with the Dolby SR noise reduction process? If so, do the processors - DA20, CP500, CP650 - apply SR decoding to the recovered digital audio tracks? Is it understood that the commonly used " SRD" naming convention means the SR noise reduction process only applies to the analog soundtracks or both the analog and digital tracks on the film?

Thank you, Paul Finn

The purpose of noise reduction is to reduce the noise floor on the optical soundtrack. The digital soundtrack already has 110dB of dynamic range, adding an analog process to that would only raise the noise floor. It's kinda like DBX encoding CD's. Part of the SRD spec specified SR noise reduction for use on the analog optical track in case the digital of analog fallback.

Josh

[Ryan Gallagher]

Part of the SRD spec specified SR noise reduction for use on the analog optical track in case the digital of analog fallback.

Josh

Yeah, so if we are just picking at the use of SR in the naming convention. It is really “SR+D”. ;-)

[Paul H. Rayton]

Which is, of course, almost the name that Dolby applied in the beginning. I think, technically, it was "SR.D".

Considering this discussion, maybe Dolby should have named it "D+SR", or "Dw/SR" or something like that.

[Randy Stankey]

I suppose, if they wanted to have a cute name for it, they could have called it "Dolby SRnD" and pronounce it like "Surround."

[Mark Gulbrandsen]

What Dolby Digital really needed was a High Frequency / Harmonics Extender Card. Especially considering how often the Analog SR track actually sounded better. That way, all that missing high end could be synthesized and put back into the Digital mix.

[Lyle Romer]

I suppose, if they wanted to have a cute name for it, they could have called it "Dolby SRnD" and pronounce it like "Surround."

It would have been better than that confusing "all inclusive" logo they had before changing the marketing name to "Dolby Digital" from "Dolby Stereo Digital."

Spectral Recording
DD DOLBY STEREO
DIGITAL
In Selected Theatres

I'm not sure how any average customer was supposed to figurer out what that meant on the poster.

[David Ferguson]

I think the customer was just supposed to see "Dolby" and think "that means it's good, right?". You still see this today, with THX and Atmos branded cheap laptops... honestly, how can a _laptop_ have "Atmos"?

The original DA10 unit didn't have "Dolby Digital" written on it, it had "Dolby Stereo" instead. So too did the first run of DA20s - it was later that it was changed to "Dolby Digital".

Dolby initially thought that SR•D would be like 70mm - only for the high end, large, and roadshow venues. They thought that SR (which sounds brilliant when setup correctly) would be more than enough for the average screen. SR•D was priced to match that expectation too - originally costing $20k for the DA10 and Cat. 699 set. However the lure of the "digital" word meant that everyone wanted digital, and then the release of DTS at a much cheaper price made Dolby rethink their strategy - so much so that they discounted it, and apparently gave refunds to those who had bought it at full-price.