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3D Audio Standard Released

Posted by timothy on from the if-you-had-a-pair-of-ears-on-the-back-of-your-head dept.

CIStud writes The Audio Engineering Society (AES) has released its new 3D Audio Standard (AES69-2015), covering topics such as binaural listening, which is growing due to increased usage of smartphones, tablets and other individual entertainment systems that offer audio using headphones. AES states that an understanding of the way that the listener experiences binaural sound, expressed as head-related transfer functions (HRTF) facilitates the way to 3D personal audio. The standard also looks into convolution-based reverberation processors in 3D virtual audio environments, which has also grown with the increase of available computing power.

15 of 82 comments (clear)

  1. i don't get it..... by Anonymous Coward · · Score: 2, Interesting

    binaural = stereo
    3d audio = surround sound (5.1/7.1/8.1/etc)

    both have been around forever.

    1. Re:i don't get it..... by tlhIngan · · Score: 2

      binaural = stereo
      3d audio = surround sound (5.1/7.1/8.1/etc)

      both have been around forever.

      As have speaker virtualization.

      This is basically another form of speaker virtualization - the ability to simulate a surround sound system using headphones. They do work (since you only have two ears, they just have to reproduce how your ear hears each speaker), and they do keep you from having the "inside your head" feeling you get with stereo sound played on normal headphones.

      However, it's a bit more flexible in that you don't just have a virtual surround setup playing discrete channels of audio. Instead, it lets you position sounds, then simulates how it would sound if it was actually happening and plays that modified audio to your headphones, so it appears that the object was at the location.

      Most virtualization systems (Dolby Headphone, DTS Headphone, Virtuaphone (Sony proprietary) and others) use HRTF (head-related transfer function) methods to compute how audio that's heard at some location in space will be heard by someone so it can be downmixed into two channel audio.

      This is but yet another one. And I'm sure not the last - a few game engines also have the ability to compute 3D audio.

      The other way of doing it is fine if the objects are located in discrete locations - there are a few virtualization systems that use convolution filters by having impulse responses measured from sources at discrete locations and how they're received by microphones.

    2. Re:i don't get it..... by bill_mcgonigle · · Score: 2

      binaural = stereo
      3d audio = surround sound (5.1/7.1/8.1/etc)

      No, binaural is one presentation modality for a 3D soundstage. You could do it with any given set of speakers if you have the right convolution matrix. Stereo imaging was what I worked on for an undergrad project in the early 90's. We had 5.1 available at the time and nobody called it '3D audio' - "Surround Sound" was the common parlance.

      --
      My God, it's Full of Source!
      OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
    3. Re:i don't get it..... by iluvcapra · · Score: 3, Interesting

      3d audio = surround sound (5.1/7.1/8.1/etc)

      "5.1/7.1/8.1" doesn't have an elevation component. Certain IMAX formats did, as did some experimental 70mm formats in the 70s, but it hasn't really been widely available before Dolby ATMOS and Barco Auro.

      The big difference with the traditional X.Y formats is these regard individual screen channels as discrete, and when films are mixed, sound sources are hard-assigned to certain speaker channels, and the speaker placement has to be matched in every venue . "3D" systems use procedural methods to assign sound sources a vector or coordinate with metadata, and a decoder at the receiving end does the job of assigning speakers, which may have different placement and number from venue to venue.

      Something mixed in 5.1 or 7.1 can be "downmixed" to stereo by summing channels together and applying pan and gain to position the multichannel sources in a stereo field. But a stereo signal can't really be "upmixed" to a 7.1, the position of individual sound sources is lost and can't really be extracted from the mix -- there are fancy ways of "spatializing" stereo mixes to 5.1 or 7.1 with fourier analysis and panning certain phase correlations or frequencies to different speakers, but there's really no way for a spatializer to split the celli from the violas and pan them separately, or the machine guns and the explosions.

      3D audio formats keep violas and cellis on separate streams in the file, and then use position metadata to do the speaker mix in the receiver, so something mixed on stereo or 5.1 speakers could be unmixed to a 7.1, or 11.1, or 64 channel setup and you would actually get more fidelity.

      --
      Don't blame me, I voted for Baltar.
    4. Re:i don't get it..... by steveha · · Score: 3, Interesting

      binaural = stereo

      Actually in the audio world, "binaural" is used to specifically mean a recording intended for being played directly into the ears.

      I was once present for a binaural recording session. The guy doing the recording had brought a fake human head, and the two microphones for the recoding were positioned in the two ears. The idea was to reproduce as fully as possible what you would have heard if you had been sitting in that spot in the room, with your head in that position.

      You can listen to a binaural recording on speakers of course, but for the best experience you should use headphones.

      For the absolute best experience, the recording should use a fake head that is exactly like your head. Not many people are ever going to experience that.

      http://en.wikipedia.org/wiki/Binaural_recording

      Audio can do funny things as it travels around your head. For the absolute best 3D experience with headphones, you want to measure what happens to audio around your head; this is called your "Head-Related Transfer Function" or "HRTF". Instead of recording the audio with a fake head shaped just like yours, companies can just record a good 5.1 or 7.1 recording, and then you can mix that down to a binaural stereo mix that is perfect for your head if you have your HRTF. According to the article the AES is standardizing a file format for HRTF data, so that the software you get will be more likely to be able to work with your HRTF data if you have it measured.

      The ultimate in VR audio will be headphones with motion tracking, and real-time mixing that uses your HRTF and changes the mix as you turn your head. If something is supposed to be coming from your left, and you turn your head to the left, that sound should get louder; then if you turn your head away from it, it should get quieter. If this is done right it should be incredible. People have been working on this for years and I'm sure someone somewhere has done it right, but I haven't seen any commonly available products to do it yet.

      But with VR goggles you should totally have VR audio like I described above. It would be really immersive.

      3d audio = surround sound (5.1/7.1/8.1/etc)

      Pretty much, 3D audio is intended to include speakers above the plane of the 5.1 or 7.1 speaker setup; the industry calls these "height speakers". DTS 11.1 audio, for example, has a standard 7.1 setup, and then 4 height speakers: two in the front and two in the back.

      The current ultimate in 3D audio is a 22.2 setup, where the ceiling has a 3x3 array of speakers, there are speakers at mid height, and there are speakers at ground level. However, IMHO there is zero chance that 22.2 will catch on as an audio standard.

      Before the 5.1 and 7.1 digital standards, there was Dolby Surround that was encoded within a stereo soundtrack. A simple audio mixer could "upmix" from stereo to surround. DTS Neural Upmix can make a very clean 7.1 from a stereo signal, and it works from an analog signal (it's not something tricky inside a digital encoded format). You can't get 8 kilograms of flour into a 2-kilo bag, and Neural Upmix 7.1 can't completely reproduce the same mix as you can play through 8 discrete channels, but it can provide a good experience.

      DTS 11.1, as I understand it, uses technology similar to DTS Neural Upmix to encode the 4 "height" channels within the other 7.1 channels. Turning 7.1 into 11.1 should be a lot easier than turning 2.0 into 7.1 so it should provide a good experience.

      I expect the industry to go to "object oriented" audio. This means that audio will have metadata tags saying what direction the audio is coming from, and then a real-time mixer upmixes from the digital format with the metadata tags to whatever mix you need (i.e. if you have 11.1 speakers you get an 11.1 mix, if you actually have 22.2 speakers you get that, if you have 7.1 you get that, etc.) I believe Dolby Atmos works this way, and I believe DTS

      --
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  2. Monster cables by Anonymous Coward · · Score: 5, Funny

    This is going to sound incredible on gold plated 3d monster cables!!

  3. And another DRM loop to jump through... by rodrigoandrade · · Score: 4, Insightful

    Let's not forget that this means new DRM and additional difficulty to get shit that we paid for working together.

    1. Re:And another DRM loop to jump through... by rodrigoandrade · · Score: 4, Insightful

      Every new digital technology improvement in the A / V / videogame department has brought new DRM with it. I can't see how this time it's going to be different.

  4. Re:OpenAL? by ilsaloving · · Score: 2

    Or, you know, I could RTFA and find out that it's actually an effort to create a FILE FORMAT for sharing 3d spatial audio data. Dunno if there's already such a thing, but if there isn't then it definitely makes sense to have one.

  5. Re:Could be promising by Anonymous Coward · · Score: 3, Interesting

    Back in the late 90s, my $20 A3D soundcard faked 3D sound so well, I could shoot people through walls in Counter-Strike. It was like I could "see" with my ears. I know several other friends who had this same experience. Ever since A3D got sued out of existence by Creative, I have never heard such good stereo 3D sound. Headphones are superior to speakers because the headphones remain fixed, equally distanced, not affected by the surrounding environment, and the sound from one does not bleed into the other unless explicitly done.

  6. Re:Could be promising by iluvcapra · · Score: 2

    This could be quite promising if incorporated into movies and video games.

    There are already several platforms for object-based 3D audio in games, they already offer solutions for binaural and HRTF listening.

    The AES has promulgated many standards with regard to file interchange and computer audio, they're always several years behind and chasing proprietary vendor technology that's already established (See AES31, a timeline interchange format supported by no one, even open source projects avoid it like the plague). In the end vendors have nothing to gain by adopting the AES standard.

    On the videogame side there's OpenAL, X3d and a bunch of other platforms that build on these. Speaking as a film sound designer, 3D audio systems just don't offer the level of control I'd want: I don't want the user's cellphone applying my fucking reverbs and distance rolloffs for me, and nether do my clients. This is why there's Dolby ATMOS and the competing Barco-DTS standard which will probably be FRAND and offer down mixing modes which should preserve the experience on headphones, and don't leave things like equalization, or panning, or reverb to the interpretation of the platform or the host.

    --
    Don't blame me, I voted for Baltar.
  7. Aureal Vortex 2 by J-1000 · · Score: 2, Insightful

    Interactive 3D sound was incredible on my sound card with a Vortex 2 chipset back around 1999. After their acquisition by Creative Labs I've heard very little good 3D sound. Is it really that uncommon, or am I just numb? Seems odd that we're still trying to get this figured out.

    1. Re:Aureal Vortex 2 by Dutch+Gun · · Score: 3, Insightful

      We're not still trying to figure this out. It's that we *can't* use it.

      HRTF is a patent minefield, thanks to Creative Labs and a few others. It's extremely difficult to develop decent software HRTF functions without stepping on someone's patent. No one in the videogame industry bothers with hardware acceleration anymore as it's not supported, and even if it were, is far too limiting (think fixed-pipeline versus shader-based rendering). As such, we're pretty much stuck with basic pan/volume simulation of 3D sound, perhaps with a bit of low-pass filtering if you're lucky.

      Fortunately, many of those patents should be expiring soon, and CPUs are now plenty powerful enough to perform those calculations in software. So, we may see high-quality HRTF functions make a comeback in the next five years or so. Kind of sad, really.

      --
      Irony: Agile development has too much intertia to be abandoned now.
  8. Re:Could be promising by Theaetetus · · Score: 3, Insightful

    > but also because I can get much better sound quality out of headphones for a fraction of the price of comparable speakers.

    Doubtful. The distance between your ears and your headphones are far from long enough to experience lower frequencies.

    That makes no sense, both from a physics standpoint and a common sense standpoint. For the former, sound is varying air pressure over time. Distance doesn't come into it, and you don't need to run around in a space to hear low frequencies.

    For the latter, the distance between ear buds and your eardrum are approximately what, half an inch? Sound travels at about 1000 ft/sec, or conversely, has a wavelength of 1 ft at 1kHz, 1 inch at 12 kHz, and a half-inch at 24kHz. If your ability to hear low frequency depended on the distance between your ear and the source, then no one wearing earbuds could hear anything below 24 kHz, right? And since most people can't hear above 20kHz, then ear buds would just be silence generators, right?

    Or, if you wanted to hear the rumble of an approaching train in the distance, you wouldn't put your ear on the track because "the distance between it and your ear wouldn't be enough to hear low frequencies" and instead, you'd want to stand several feet away?

    In fact, as noted above, the wavelength of 1 kHz sound wave in air is 1 ft. At 100 Hz, it's 10ft, and at 20 Hz, it's 50 ft. How many people have 50 feet between their ears and their speakers? Or even 10 feet in most living rooms?

    Your post makes no sense, no matter how you think about it.

  9. Re:Obligatory? by CronoCloud · · Score: 2

    By Your Command.

    http://xkcd.com/927/