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Comment by ugjka | Hacker News Reader

What's the problem?

When the sound design is targeted for 5.1, most of the dialogue comes from the center speaker.

This is great if you have one.

However if its downmixed on the fly (ie done on the client side) the center channel is often just played out of both speakers. This means that sound can be muffled, because its drowned out by the incidental noise that comes from the left/right channel.

> the center channel is often just played out of both speakers

Well what other option do you have when there are only two speakers? Only play it out of one?

The next sentence explains why this is a problem.

> This means that sound can be muffled, because its drowned out by the incidental noise that comes from the left/right channel.

Yeah I read the same comment you did, but if you're taking a signal with 6 channels, and only have two channels out, you don't really have any option but send the middle channel to both outputs, else it'll sound far too intense in a single ear.

A separate stereo audio mix.

How else would you mix the dialogue except to come out of both speakers though?

Just make it a bit louder, before summing it into the left and right channel

Right... so why isn't that done already from the 5.1 signal?

I have no idea why that’s not being automatically done when the mixdown occurs in the player.

Because other times when it's not dialogue (or even when it is--the busy/crowded street effect) you may not want the center channel gain to be raised during mixdown.

Consumer hardware can only guess. A sound engineer can know.

You mix the dialog louder for the entire piece, and every other sound in the middle. No extreme highs, no extreme lows. General compression with dialog forward choices.

I don't know why compression isn't built in to consumer media devices, it's so often called for (and closely followed by volume normalisation ... but I guess the advertisers veto that).

> I don't know why compression isn't built in to consumer media devices

As always, it depends on the device. Dynamic range compression seems to be a relatively common feature, usually as an option described (inaccurately) with something like "Reduce Loud Sounds" like it is on the Apple TV.

The center channel needs to be made louder in the mixdown to 2 channels

But why can't that be done automatically from the 5.1 signal on the consumer's device?

Exactly and I have no idea, why this is not done - is it a technical reason, or is it lazy consumer device programming?

It could. But it's an artistic and a sound engineering decision that changes based on what you actually want the listener to hear.

The defaults for automatic sound mixing will almost always be wrong. And they will differ in how they are wrong from consumer box to consumer box.

If wonder if instead of a separate mix, 5.1 could be modified to include hints for how to better down-mix a given production.

It can. That's part of the Blu-ray spec. But it's not standardized in streaming video AFAIK (not that Netflix has to care about that, they have their own player) and, even if the feature exists, somebody still has to go do it.

A speech recognition model can give you a reading on how understandable the speech is and use that information to guide the channel volume in the mixing.

OTOH, a lot of the models end up trained on features that are very different from what humans hear.

No,

When you master for 5.1, because you have the centre speaker, you can have dialogue at 100% volume, then out of left and right, you can have incidental noise, be that music or "atmosphere" also at 100%

(its been a while since I've mastered in 5.1) However, two channels of 100% volume (well 0dbu) is louder than just one channel. Which means that if you have lots of music, wind or other foley it'll drown out the dialogue.

It requires artistic choices from the sound team to make work properly.

Wild volume swings, insane punches for explosions but silent dialogue.

It’s SOP for Hollywood. Sad we’re not getting Real Innovation around this problem.

Yeah, I have no interest in surround sound, I just want to hear the words. I specifically don't want to be rumbled by gunshots and explosions.

Blueray supports downmix metadata that I think lets you mix volumes with the full 6x2 matrix, and I don't remember if there's EQ but there may be. Also a 5.1 AV is like 500 bucks if you have the space. I don't think what other innovations you need. The technology to stream different audio streams and let the user choose is there.

Thing is most studios now do only one mix for theaters and also most streaming providers don't give many fucks about audio. It's not an innovation problem it's a product problem.

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