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Comment by gwbas1c | Hacker News Reader

From https://en.wikipedia.org/wiki/Dolby_Digital#Cinema

> Dolby Digital cinema soundtracks are optically recorded on a 35 mm release print using sequential data blocks placed between every perforation hole on the sound track side of the film. A constant bit rate of 320 kbit/s is used. A charge-coupled device (CCD) scanner in the image projector picks up a scanned video image of this area, and a processor correlates the image area and extracts the digital data as an AC-3 bitstream. The data is then decoded into a 5.1 channel audio source. All film prints with Dolby Digital data also have Dolby Stereo analogue soundtracks using Dolby SR noise reduction and such prints are known as Dolby SR-D prints.

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All correct (as far as I'm aware), except for the unfortunately common inaccuracy that Dolby Digital on film is AC3. Sadly it's not - it's an earlier iteration of that technology that's incompatible. It must be pretty similar, though.

You can edit the Wikipedia article.

What makes you believe the GP is correct and whoever wrote that in the article is wrong, or that either are correct?

My knowledge comes from someone who helped develop Dolby Digital on film so I'm pretty sure it's correct.

Sorry, I didn't mean to comment on your expertise, but rather the epistemology of who we believe.

> My knowledge comes from someone who helped develop Dolby Digital on film so I'm pretty sure it's correct.

That is certainly better information than anyone else here has, and you seem to actually understand the technology. I wish HN was 90% comments like yours and almost none of the rest, especially Wikipedia!

But while we're talking about epistemology! Decades-old memories go wrong, and when vested interests are involved the memories can drift to desired beliefs or familiar narratives. That doesn't make the comment a bad one - it's very valuable, actual knowledge. But it's not sure to be correct either, and/or not precise.

Absolutely true and I agree with you. Something else to back up that it's not quite AC3 is that I've captured the raw signal that goes into the decoder box's "AC3-decoding card", and it's not quite what I'd expect for AC3. You can learn more about that and download the raw signal capture at https://fanrestore.com/thread-2633-post-73179.html#pid73179

Holy cow, what an amazing-looking community! What is going on there? Who is behind it? And when people restore a work, can they share it with other members?

They don't let you put stuff on Wikipedia just because you happen to know it's true, right? You have to launder it through a source first.

I suppose he could get away with nobody adding the [citation needed], but that'd be against the rules.

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