[CT007]

This question came to me today: Which would be more accurate/correct in a 3D game that supported both HRTF for stereo headphones and surround sound for 4-7 speakers? (the speakers are only in surround sound mode, not HRTF also, and no other special software is used)

Surround speakers would be very difficult to set up perfectly, so that the speakers are at the correct distances, rotation/toe-in/toe-out, and circumferential placements, to the user, to reproduce perfect timing/sync and imaging placement cues. Headphones/IEMs are a set system, that would only suffer from room noise, compared to speakers, unless they were a closed-back model.

Another question is: Is there something that has been specially designed into HRTF software where a perfectly set up surround speaker system would not be able to reproduce sound as correctly/realistically, in a 3D game/environment?

I am very curious to see what the test results would be between these 2 systems, in ideal configurations and room environments.

 

[bigshot]

I've had friends use my home theater with projection and 5.1 for gaming. They seem to think it works well. 5.1 is a standard for speaker configuration. In theory that should allow consistent and accurate sound placement.

 

[CT007]

5.1 is a standard for speaker configuration

Yes, this is a surround standard for home movies, at least, too. I wonder what config is actually used in theaters? Still 5.1, but each channel is expanded across 2-4 speakers?

HRTF takes a stereo source(designed for speakers?) and tweaks it to sound correct for headphone use. Surround sound, for surround speakers, needs more channels and therefore more unique audio data, to properly operate. So, you would think more channels should mean more information and more positional accuracy (assuming the speakers are set up perfectly).

 

[bigshot]

With Atmos, you can have more channels and speakers than just 5.1. It's scalable. They have Atmos for both home and theaters.

 

[CT007]

I don't really know about Atmos, except it's a speaker technology, I think, that adds more vertical information via upward angled floor speakers, perhaps by artificial means, not actual vertical channel information?

 

[sander99]

HRTF takes a stereo source(designed for speakers?) and tweaks it to sound correct for headphone use.

Actually it is a little bit different.

First:
HRTF is short for Head Related Transfer Function. Sound coming from around you is filtered when bending around your head and into your ears. This filtering is different for different directions and gives the brain clues (in addition to level and time differences between the ears) for localizing sound sources. Also it is different for different individuals, because we all have different shaped heads and ears. Your HRTF describes how the sound is filtered by your head and ears for all different directions (or in practical applications: for a large set of directions).

Using one's HRTF it is possible to generate binaural simultions of sound sources in any location and distance. That means you can play it over headphones and it will sound as if it is coming from a certain direction and a certain distance. In particular it is possible to binaurally simulate any number of loudspeakers in different positions around you. And this can be combined with headtracking such that the virtual loudspeakers stay in a fixed position if you move your head. This works best using your own personal HRTF. Some systems try to do it using a generic HRTF, for example measured with a dummy head. This gives varying results, depending (amongst other things) on how average your HRTF is, or how sensitive your brains are to errors in the HRTF. To some it can sound reasonable, to others totally unconvincing and strange.

So when simulating a multichannel loudspeaker system over headphones you can start with a multichannel source (instead of a stereo source) that is binauralized (which is effectively a sophisticated downmix to stereo). (And it will retain all the "information and ... positional accuracy" of the multichannel source).

When done correct this can compete with a real multichannel loudspeaker system. Maybe not 100% equal but it can come very close. And there can be some advantages. With virtual speakers over headphones you don't have to worry about your room acoustics or disturbing your neighbours.

Now if some specific game has it's own "HRTF for stereo headphones" and also supports multichannel speakers then chances are that the former can not be personalized to your personal HRTF, and doesn't give optimal results. So in that case using multichannel speakers is probably better. But a third possibility is to take the multichannel audio output and use an external device to binauralize that for headphones. For example a Smyth Realiser A16. (Unfortunately that is very expensive.) But hopefully there will be more (and more affordable) alternatives.

I don't really know about Atmos, except it's a speaker technology, I think, that adds more vertical information via upward angled floor speakers?

It is a surround format that uses height or ceiling speakers (and alternatively upfiring speakers can be used instead of real height or ceiling speakers).

 

[CT007]

Actually it is a little bit different.

First:
HRTF is short for Head Related Transfer Function. Sound coming from around you is filtered when bending around your head and into your ears. This filtering is different for different directions and gives the brain clues (in addition to level and time differences between the ears) for localizing sound sources. Also it is different for different individuals, because we all have different shaped heads and ears. Your HRTF describes how the sound is filtered by your head and ears for all different directions (or in practical applications: for a large set of directions).

Using one's HRTF it is possible to generate binaural simultions of sound sources in any location and distance. That means you can play it over headphones and it will sound as if it is coming from a certain direction and a certain distance. In particular it is possible to binaurally simulate any number of loudspeakers in different positions around you. And this can be combined with headtracking such that the virtual loudspeakers stay in a fixed position if you move your head. This works best using your own personal HRTF. Some systems try to do it using a generic HRTF, for example measured with a dummy head. This gives varying results, depending (amongst other things) on how average your HRTF is, or how sensitive your brains are to errors in the HRTF. To some it can sound reasonable, to others totally unconvincing and strange.

So when simulating a multichannel loudspeaker system over headphones you can start with a multichannel source (instead of a stereo source) that is binauralized (which is effectively a sophisticated downmix to stereo). (And it will retain all the "information and ... positional accuracy" of the multichannel source).

When done correct this can compete with a real multichannel loudspeaker system. Maybe not 100% equal but it can come very close. And there can be some advantages. With virtual speakers over headphones you don't have to worry about your room acoustics or disturbing your neighbours.

Now if some specific game has it's own "HRTF for stereo headphones" and also supports multichannel speakers then chances are that the former can not be personalized to your personal HRTF, and doesn't give optimal results. So in that case using multichannel speakers is probably better. But a third possibility is to take the multichannel audio output and use an external device to binauralize that for headphones. For example a Smyth Realiser A16. (Unfortunately that is very expensive.) But hopefully there will be more (and more affordable) alternatives.


It is a surround format that uses height or ceiling speakers (and alternatively upfiring speakers can be used instead of real height or ceiling speakers).

Ah... So you need to perform an HRTF calibration profile, per headphone(?), to achieve best results. This explains all of the 60+ HRTF preset profiles for games I've seen with the OpenAL implementation. I've never seen or heard of HRTF calibration done before, or profile saving/creating. I suppose this would be done externally, outside of the game, ideally, and most simplistically. The possibilities of future game audio are so exciting... but don't seem to be moving very quickly at all :/

Feel free to post any related videos or articles that discuss/explain these topics further!

 

[bigshot]

Ah... So you need to perform an HRTF calibration profile, per headphone(?), to achieve best results.

Per person... Everyone's noggin is shaped a little different and that affects the sound.

 

[CT007]

Per person... Everyone's noggin is shaped a little different and that affects the sound.

If you had external HRTF hardware, and then were simply able to set in-game audio to "headphones", I wonder how much audio delay the HRTF processing would incur.

 

[bigshot]

Some simulators have head tracking, so there can’t be latency.

 

[CT007]

Ah... That's a feature I never want lol.

 

[bigshot]

Otherwise when you turn your head, all the sound turns with you. Head tracking is a huge part of sound location.

 

[CT007]

It's a gimmick to me, because I would never turn my head away from the screen, in actual use.

 

[castleofargh]

Ah... So you need to perform an HRTF calibration profile, per headphone(?), to achieve best results. This explains all of the 60+ HRTF preset profiles for games I've seen with the OpenAL implementation. I've never seen or heard of HRTF calibration done before, or profile saving/creating. I suppose this would be done externally, outside of the game, ideally, and most simplistically. The possibilities of future game audio are so exciting... but don't seem to be moving very quickly at all :/

Feel free to post any related videos or articles that discuss/explain these topics further!

As explained by others, the more the measurements come from your own body, the better the subjective results.
The typical and still most reliable method, for now, is to play sine sweeps through actual speakers and record the sound with binaural microphones in your ears (so the recording has most of the changes caused by your very own head and outer ears). Then those sweeps are used to create impulses that will be used to replay any audio with the signature, delay, reverb of a particular channel/speaker from a particular direction. You could do that for as many channels as you want, but Windows alone can already limit what you can use above 8 channels.

A starting point for practical use would be https://github.com/jaakkopasanen/Impulcifer and the thread to discuss it and how to use it: https://www.head-fi.org/threads/recording-impulse-responses-for-speaker-virtualization.890719/
No head tracking, and all you need to invest in is a pair of binaural mics (maybe an ADC if specific plugs are on the mics) and some of your time to figure it all out and to try various little tweaks to your recordings. You do need speakers, you can manage to record many position with just a pair, but you can't do anything without some speakers.

Fast tour of sound localization using headphones with sound samples https://www.audiocheck.net/audiotests_stereophonicsound.php
All the general ideas about human perception of direction (not specific to headphones) are on Wikipedia https://en.wikipedia.org/wiki/Sound_localization, and you can start guessing how much a headphone interferes with those usual cues.
After that, I don't know how deep down the rabbit hole you are planning to go. Acoustics, psychoacoustics, audio formats handling virtual sound sources, possible tools. It's a hobby within the hobby.

If you had external HRTF hardware, and then were simply able to set in-game audio to "headphones", I wonder how much audio delay the HRTF processing would incur.

This depends on a few variables, but usually people who code/design those apps or devices, logically give priority to reasonably low latency.

It's a gimmick to me, because I would never turn my head away from the screen, in actual use.

I understand that, I'm not even sure I blink when I play a fast-paced game. And yet, turning our head, even a little, is a gold mine for positional cues.

 

[sander99]

99% of all music is recorded in stereo. And the cost of having to get 7 high quality speakers. Stereo works just fine.

Sure. But over 90% of all movies, and a lot of games, have multichannel audio. And with virtual speakers over headphones you don't have to buy 7 real speakers. By the way: stereo music also sounds great with 2 virtual loudspeakers over headphones. At least half the time that I use my Realiser is with stereo sources over 2 virtual speakers.