Saturday, June 13, 2015

Re: [Avid-L2] Export Dolby AC3 from MC7 timeline?

 

"...but true Dolby Digital 5.1/7.1 is not "stored as 2 channels"."

I do see stations OTA that are transmitting dolby digital AC3 5.1 but it is stereo with no center speaker.  My basic understanding is there is a metadata flag that tells the decoder what's up.  What I notice on the CBS affiliate is prime time network has a center speaker etc.... but when it goes to local news the dialogue comes out the stereo front speakers not the center speaker.  The receiver sees it as a Dolby Digital source but only two channels come out.  I guess that's what you mean by "true dolby digital 5.1.



---In Avid-L2@yahoogroups.com, <Job_L2@...> wrote :

On 11 jun. 2015, at 21:09, Nick Hrycyk bigblueav@... [Avid-L2] <Avid-L2@yahoogroups.com> wrote:

> The ac3 output file is an encoded 2 channel surround sound file. Played back decided you will get full surround.

I believe that is incorrect. The old 4-ch matrixed Dolby surround (Dolby Stereo) folded 4 ch of mix back to 2 tracks, and the result was a stereo compatible LtRt track, which, when played back through a Dolby Matrix would give you LCRS again. That was upped to Dolby Pro Logic II which allowed for 5.1 channels to be folded into 2 channels via a matrix, and unfolded upon playback. And a Dolby E track (5.1 or 7.1) can be stored on 2 ch of PCM audio, but true Dolby Digital 5.1/7.1 is not "stored as 2 channels".

There are quite a few encoders that let you encode 2 ch stereo mixes into AC3. There are very few that let you encode a 5.1 mix into AC3, because Dolby asks a premium for that.

Apple DVD Studio Pro used to come with A-pack, which takes 6 PCM channels and lets you encode them into an AC3 file for DVD/BD authoring.

I've one time used something like this as well: http://www.softpedia.com/get/Multimedia/Audio/Audio-CD-Rippers-Encoders/WAV-to-AC3-Encoder.shtml or this http://www.hootech.com/formats/ac3/convert-wav-to-ac3.htm

Again, I think the culprit is that Adobe won't let us add 6 PCM channels. The BD specs allow it. A lot of commercial disks have it. No encoders needed. More bandwidth, that's true, but also pristine sound quality. And on a 25GB BD, there's plenty of room anyway.

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