On the specs page for Samsung Milk VR they list acceptable delivery formats: Mono, Stereo, 5.1, binaural and quadraphonic. Then they list binaural as having 4 tracks. My understanding of binaural is that it is a stereo format. Track assignments also appear to be identical to the quadraphonic format. Thoughts?
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I have also asked this question to the support people at Samsung and will post if they reply– ReedCommented May 11, 2016 at 19:00
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2 Answers
That's what they call "omni-binaural", captured with microphones like this one.
It provides 4 stereo independent binaural channels, one channel for each direction+orientation. On VR video playback, a linear mix of the different channels is made, depending on the actual momentary orientation of the user.
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Interesting. Any idea how to encode a mix for omni-binaural? Also, to be clear I still don't see how this differs from the delivery of a quadraphonic mix as Samsung has it listed. Both formats allow for 4 mono or stereo tracks and both use the same definition for each track (Track 1 = 0 degrees, 2 = 90 degrees, 3 = 180 degrees, 4 = 270 degrees). Is the binaural format taking into account HRTFs?– ReedCommented May 12, 2016 at 17:43
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I'm not familiar with the production process for VR systems proper, sorry. But I would expect the omni-binaural would not require specific enconding (I mean channel enconding, not audio enconding), as each captured channel is going to be directly fed to the respective input channel. But it would have to be sound captured with an omni-binaural mic. Quadraphonic input would be to feed a "mix" generated by means other than omni-binaural (studio produced movie soundtrack, musical audio, etc.) Clarification, not both formats allow either mono or stereo, there's no such thing as mono binaural. Commented May 12, 2016 at 17:57
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You may be right. Hopefully Samsung will answer and I can say for sure. Regarding mono/stereo, I am just quoting the spec sheet. They do allow 4 mono tracks.– ReedCommented May 12, 2016 at 18:23
Samsung responded to my request:
Hello Reed—
Thanks for your outreach and inquiry. We've recently updated our content specifications to better address this issue. Please refer to the section under "Additional Audio Formats".
Content Specs: https://samsungmilkvr.com/portal/content/content_specs Sincerely, Samsung Milk VR Support
Here are the updated specs:
"Binaural audio: 4 mono or stereo audio tracks need to be present in the mp4. MilkVR will constantly mix exactly two of them for head tracked spatial audio. The order of the tracks must be as follows: 0 degrees (front), 90 degrees (right), 180 degrees (back), 270 degrees (left). For example, when the user is looking at 45 degrees, approximately 50% of the first audio track and 50% of the second audio track are mixed. At 90 degrees, 100% of the second audio track is played.
Quadraphonic audio: 4 mono or stereo audio tracks need to be present in the mp4. MilkVR will play a different audio track for each of the four 90 degree cardinal directions a user looks in the video. The engine will fade between two of the tracks when the user is close to crossing into the next quadrant. The order of the tracks must be as follows: 0 degrees (front), 90 degrees (right), 180 degrees (back), 270 degrees (left). A good example of this audio format is the MansLaughter - An Experiment in Theatrical VR video, which can be found on the MilkVR service by searching for MansLaughter.
The main difference between binaural audio and quadraphonic audio is that binuaral will constantly mix two tracks at any given time while quadraphonic will only play one track at any given time (with the exception of the corners). Binaural audio is generally the preferred choice for most 360 videos. We envision quadraphonic audio most applicable to a 360 video with each quadrant having a different scene with a distinctly different audio track."
Very useful update.