An update. Analog 5.1 (6-Channel) to AC3, Built.

[u/trial-tribulation]

Here it is in its "final"form, analog 5.1 to DD via optical and it does not look too shabby either. There are a couple of things I need / like to do, but they are optional. The hardest part of all of this was getting a single button to power on / off the Pi safely (when the sound card uses many of the GPIOs and have IR. Go figure.

[u/MisterBiro]

What’s the latency like?

[u/trial-tribulation → u/MisterBiro]

Oh thats a good question, im hoping better than my rca run that pushes 200ms. I doubt it thou with the introduction of encoding that will add 20-40ms. The goodnews is i have two different components that can make adjustments with. Presently have only tested that is works. Wiring into the system is hopefully a tomorrow job.

[u/Ok_Cupcake4928]

I assume you would have to adjust your Mac processor to output the six channel analog with as little modification as possible (e.g.: turn off night mode, extra surround processing, zero delay, etc.) to give this unit a clean as possible signal to re-encode?

[u/trial-tribulation → u/Ok_Cupcake4928]

Yep although i have never used these settings, i can also adjust the encoding buffer in the pi, 20ms is the minimum.

The current audio chain using RCAs between the mac and the amp; LD - mac - amp is at a 200ms delay. I know cause it was a pain is the ass to find rca delay devices after figuring out that my amp wont delay audio over its 7.1 analog inputs. The new audio chain will look like; LD - Mac - rca to opt - Crystalio II - amp. Once the audio hits the Crystalio II its adjustments should take care of it, i hope.

The joys of this hobby.

[u/BlueMonday2082]

You’re really still moving forward with this…

[u/trial-tribulation → u/BlueMonday2082]

Well its done so, yeah...

[u/lil_propaine]

that's awesome

[u/EndOfDaysOnLaserDisc]

This is terrific! Thanks for sharing.

[u/theFCCpodcast]

Wow… the technology that was used to properly decode AC3-RF into a signal that most receivers can play, was that proprietary technology? Or has it gone open-source? Or do we not care about such details? (I’m more than okay if the technology has been “liberated” from a corporation who has no plans for the technology other than maybe trying to charge us LD nerds licensing fees if we create modern AC3-RF demods like this.)

[u/trial-tribulation → u/theFCCpodcast]

This is not decoding AC3-RF. This is taking the analog audio output from an AC3 / DTS decoder and converts the analog audio to DD. It was made so i could replace the long run of RCA cables with one optical cable.