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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.

5 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 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.

      --
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    2. 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. 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.

  3. Re:Could be promising by Anonymous Coward · · Score: 1, Interesting

    You're not wrong. I worked for a company selling an audio card that featured the Aureal A3D engine, and it was incredible compared to even what people are doing today.

    A clear example of "If you can't compete, sue." Also a clear example of patent law snuffing out innovation, rather than fostering it.