Dolby Digital Encoder Does Not Support Any Encoding Options

Question

Is it just me, or are there no encoding options for the Dolby Digital encoder other than the bitrate?
How are you supposed to select the dialog normalization, dynamic range compression profile, etc. for your audio? Without these parameters set correctly, the audio will not be encoded correctly.

Answer 1

@jbowden:
> Adobe licenses the AC3 encoder that Encore uses from Dolby Laboratories. This is stated quite clearly in the splash screen, the box, and other materials distributed with Encore.
I didn't say otherwise. But what they license is the code, not the implementation. Implementations are supposed to be submitted to Dolby for approval, and I'm surprised that Dolby approved the implementation given the oversights and encoding quality.
> It's a consumer-level encoder, and if you look around this forum I think you'll find very few posts about audio quality, which would seem to indicate that Encore provides acceptable audio quality for most users. Cases with audible clipping can occur if the input signal is too high...keeping your audio signal around -6db should eliminate any clipping.
I don't buy into this whole argument about "consumer-level" and "professional-level". What is the exact difference? Dolby's code is constant across all licensed encoders, so any differences in encoding are the result of an implementation difference, and that's Adobe's fault, not Dolby's.
Audio signals are audio signals. Why do I have to keep my audio from peaking above -6dB with the Adobe encoder? I can take audio whose peaks go all the way up to 0dB and encode it with the Sonic Foundry encoder with no problem -- no clipping, no volume pumping, etc. Not so with Adobe Encore's implementation.
@Neil Wilkes:
> As far as Dialnorm goes, again I say it is pretty meaningless in a stereo file.
Dolby's encoding guidelines documents seem to say otherwise. In my readings, it seemed pretty clear that the decoder must have the dialnorm parameter set to the LAeq level of the dialog in the audio regardless of channel configuration.
> I suppose, although as long as the stereo mix is actually set up correctly there is no need to invoke DRC. The only time DRC would be needed on a stereo file is if the thing is too darn loud.
I have to disagree with this. There is a LOT of material that can benefit from DRC, both soundtracks that contain a large dynamic range (explosions to whispers), and soundtracks that have small dynamic range (speech). DRC doesn't have anything to do with the overall volume level of the soundtrack, but the dynamic range of the soundtrack. If the soundtrack is too loud overall, that's not a DRC problem, that's a level problem.
> In a properly balanced stereo file, there is no need at all for DRC or Dialnorm. There is no centre channel containing dialogue, just a phantom centre, so what are you going to reference it to, please? How can you attenuate the left/right channels with reference to the centre channel dialogue when there is no centre channel present?
Just because the dialog isn't isolated in the center channel doesn't mean you can't use it to set the dialnorm parameter. Plus, the decoder doesn't attenuate the left/right channels with reference to the center channel, it attenuates the entire soundtrack on playback.
Your quote from Dolby labs is very correct. Following that procedure ensures that the decoder, when it applies attenuation based on dialnorm and applies DRC will work as intended.
> Additionally, it is not referenced to average RMS either. RMS is close to the correct way to measure, but not correct.
That is true. However, I don't have any equipment to measure LAeq directly, so RMS of a dialog section of my audio will have to do. I do know this: When I applied to Dolby for logo usage on my DVDs, they requested samples of my DVDs for approval of my methods. My first submissions (where I didn't bother with dialnorm & DRC) were rejected, and Dolby sent me a letter telling me such. After I produced further DVDs using my method in my Doom9 post and resubmitted the DVDs to Dolby, they were approved. I can only conclude that my method, while not perfectly accurate, is good enough to qualify for Dolby's rigorous standards.
The bottom line is that I feel I have enough evidence to conclude that the DD encoder implementation in Encore is substandard. If you or anyone else feels it meets your requirements, then use it. But I for one will not allow a single DVD to go out from my company with audio encoded with this encoder.