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  1. Hey gang,

    New here, but this looks like a forum of people more experienced than me in an area Im trying to navigate. Look forward to learning from you. Hereís the dealÖ

    Im an audio engineer (and video editor) transitioning from stereo to spatial mixing this year. My studio will be receiving a monitoring upgrade in a few months. But as Iíve always been accustomed to having a home rig, Iím trying to figure out if there is a way to create a home theater setup that can also double as a secondary mix space when desiredÖ

    But first lemme get out of the way: I know I could just buy a capable audio interface (3k or more), and output to a compatible AVR (6k or more). But unless thereís solutions I donít know about, thatís thousands of dollars I canít afford. Im already spending a small fortune upgrading my actual studio and buying speakers for this home space. Plus this space is essentially my living room so itís primary use is home theater. But I sure would love and appreciate a way to use it as a secondary mix space as well.

    SoÖIs there a way one could send 12 channels of uncompressed audio from a mac to a modern AVR via hdmi 2.x?


    My ideal use case:
    - TV and AVR exist as conventional, standalone configuration, not reliant on the presence of a computer in the chain.
    - Computer is able to be looped into the system and output a real-time 12 channel mix into the system. Specifically, Pro Tools > Dolby Atmos Production Suite. (Which, just to reiterate, does *not* output a real-time Dolby stream. Rather, the real-time output for monitoring is 12 discrete, uncompressed signals, aka 7.1.4.)
    - Multichannel signal then makes its way to the AVR in some fashion.
    - AVR outputs analog to 7.1.4 speaker setup.
    - Up to at least 96 kHz would be ideal, though 48 kHz may be acceptable in the shorter term (or if source could be 96, but the stream needed to be downsampled to 48 kHz at some point for monitoring, that would be fine).
    - donít need near zero latency, per se, but need to keep things workable
    - I need to make sure audio clock remains stable on the DAW side of things.

    Hereís my (limited) understanding of the potential and the obstacles:
    - my understanding is that Mac core audio may cap hdmi audio output at 8 channels. Iíve never tried it. Is this true? I also read somewhere Monterey (beta version perhaps?) may make 12 available. anyone know if this is true?
    - I know historically hdmi itself had bandwidth limitations preventing that much uncompressed audio. But my understanding is hdmi 2.x offers plenty of bandwidth, at least on paper. Is there a way to tap into this potential?
    - I donít think the AVR Iíve got my eye on has another port available with enough bandwidth. Thereís analog inputs, but not enough, digital inputs but I think are capped at 6 channels per source, etc. But thereís a buncha hdmi 2.x ports, which is why Iím focused on delivering via hdmi (note: there is a usb connection as well for ďplaying pc audioĒ but I suspect is capped at stereo. Waiting to hear back from company with clarification on this).


    Assuming the audio can be delivered, then thereís the matter of what sort of signal the AVR could make use of. I donít know much about this domainÖA bit rate format? PCM?

    Fwiw, the AVR is capable of calibrating and outputting up to 14 analog channels of surround to my speakers. And is capable of receiving Dolby streams, dts x streams, and all previous HD formats (but not auro 3D). So while I donít anticipate being able to send an encoded Dolby or dtsx stream to the AVR, I mention all this in case it paints a picture of the broader potential pathways a stream may be able to travel upon.

    This is the unit:
    https://summithifiusa.com/products/at-300-16-channel-pre-pro-releasing-soon
    - if I can figure out how to deliver the 12 channels, itís really ideal on every other level. I know of no other AVR that can output preamped xlr signals for powered reference monitors sans a couple much more expensive (and i think discontinued) models Iíve found. Though maybe thereís other options?


    Thoughts Iíve had about how it might work:
    - DAW outputs to some sort of virtual sound card like rogue amoeba or ginger audio or Dante virtual soundcard. This would provide enough outputs for the daw, presumably an adequate clock, while also providing a way to connect to another solution that ultimately delivers to the AVR. What happens in between, I donít know.
    - And/or using ffmpeg in some way. Iíve never used it, but it it seems like there might be a way convert the signal into a stream more compatible with an hdmi path and usable by an AVR? Like a bit rate format maybe?
    - And/or using some sort of hardware that helps embed the signal into a deliverable hdmi pathway?
    - Or skipping the AVR altogether and using a focusrite rednet 16 chi instead:. DAW>Dante Virtual Soundcard> rednet > speakers. But this has lots of drawbacks it seems: Tbe 2k+ rednet strains the budget (the AVR is only 1400), Im not sure if itís possible to output decoded signals straight from the TV for home theater uses (Im getting an lg c1, anyone know?), nor am I sure if itís any easier to convert hdmi from the tv to Dante for the rednet, plus the rednet has no onboard dsp for speaker calibration, so my computer would have to be plugged in at all times (unless thereís some sort of LG app that can calibrate speakers?. Anyone know?). That said, if all these problems were solvable, and if thereís no other way to get the AVR solution to work, Iíd consider it. Or give up, lol.

    Anyone have any insight? Thanks so much!
    Last edited by Muon; 13th Jan 2022 at 01:46.
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  2. AAC is capable to support even more than 12 (48.16) channels, 8k a.k.a. Super Hi Vision audio is 22.2 - everything depends on AVR capabilities
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  3. Originally Posted by pandy View Post
    AAC is capable to support even more than 12 (48.16) channels, 8k a.k.a. Super Hi Vision audio is 22.2 - everything depends on AVR capabilities
    Thx for your responseÖjust to clarify, Iím trying to do a real-time monitoring stream. Not an encoded, mastered fileÖ.so are you referring to a real time rendered, streamable version of AAC or Super Hi Vision format?

    If so, do you have any recommendations for AVRs to look at? BC thereís plenty of AVRs that can output the channels needed, but Iíve not been able to find any that allow for more than 8 channels of input except through an encoded format like atmos or dtsÖ

    in fact, the only avr Iíve found that I thought could maybe receive that many channels was the 6k AVR I alluded to in my post, was referring to a jbl synthesis - I though I could deliver via Dante. But Iíve since learned that may not be able to possible after all, that it too may top out at 8 channels (again outside of an encoded Stream format like atmos). Waiting to hear back from a dealer who is trying to get clarifstion on that pointÖ

    Iíve also since been told on another forum ffmpeg cannot encode more than 8 channels into a deliverable format - Dolby HD was the cited example - and even if it could, the poster knew of no AVRs that could receive that many channels in that format, though he said itís technically possible if a manufacurer implemented it.

    Even trying to merely send more than 8 channels of analog doesnít seem doable to my knowledge. I talked to someone at Denon today who was not aware of a Denon that could receive more than 8 channels of analog or multichannel PCM, and every other AVR Iíve found that offers analog inputs tops out at 8 channels as well - including the TW device I linked to above. I also called a local high end home theater store and the owner knew of no solution other than a 20k trinmov processor for cinemas.

    So just to clarifyÖIíve got 12 discrete channels Im trying to deliver to an AVR (preferably the TW but open to others) but donít know how I could package and send those signals in a way an AVR could make use of themÖ.and in real time.

    So if a real time rendering method with one of the formats you listed is possible with ffmpeg, and you know of AVRs that could make correct use of the signal, Iíd love to hear moreÖ
    Last edited by Muon; 13th Jan 2022 at 16:21.
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  4. Issue is that consumer equipment probably will not support anything above 7.1 - not sure about AV Receivers supporting 11.2 and 13.2 - seem they exist but to be honest never verified reported channels number - check this list: https://tweakers.net/versterkers-en-receivers/vergelijken/#filter:HcoxCoAwFAPQu2Tu0IqK...VbdQaAqtMeecXw .

    Technically passing audio channels over HDMI you are limited by pixel clock (in case of PCM) as audio data are transmitted between video data - to accommodate more channels with high bitdepth and sample rate usually special video modes (with pixel multiplying) was used in past - not sure about HDMI 4k and 8k - perhaps they have sufficient amount of bandwidth to pass something like 12 PCM channels over HDMI.

    And apologies for all mistakes - to be honest as HDMI standard is payed i lost will while ago to follow all this crap so my information are based on pre 2.0 HDMI (but i doubt that they introduced radically new way of HDMI with 2.0)
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  5. Member Cornucopia's Avatar
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    I am wowed by your gear, and think your attempt is cool, but I expect it will lead to a dead end. Plus, you are putting a lot of effort into trying to stuff 2 systems into 1. Maybe leave it as 2 parallel systems - then you could try multiple AVRs, or a mixer board w 12 outs going analog to 12 ins directly to power amps.


    Scott
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  6. Originally Posted by pandy View Post
    Issue is that consumer equipment probably will not support anything above 7.1 -
    Yes, that's what I'm concluding. Which I guess make sense since they are manufactured to receive formats that have previously never exceeded 8 channels, though it would be interesting to discover an exception...

    Originally Posted by pandy View Post
    - not sure about AV Receivers supporting 11.2 and 13.2 - seem they exist but to be honest never verified reported channels number - check this list: https://tweakers.net/versterkers-en-receivers/vergelijken/#filter:HcoxCoAwFAPQu2Tu0IqK...VbdQaAqtMeecXw .
    I'm pretty sure none of the Denon/Marantz in that list support that many inputs BC I actually called Denon yesterday and asked. I'll dig a little deeper into some of the others soon, but not holding my breath.

    But for AVRs that are capable of receiving a multichannel PCM, I am really curious what would happen if you fed them more than 8 channels. While they may not have been designed with that in mind, I wonder if they could still receive them. Of course, you'd still have to figure out how to deliver the channels.

    Originally Posted by pandy View Post

    Technically passing audio channels over HDMI you are limited by pixel clock (in case of PCM) as audio data are transmitted between video data - to accommodate more channels with high bitdepth and sample rate usually special video modes (with pixel multiplying) was used in past - not sure about HDMI 4k and 8k - perhaps they have sufficient amount of bandwidth to pass something like 12 PCM channels over HDMI.
    That's interesting info about the pixel clock. I don't understand much about how all that works, technically, but I am aware that with HDMI the audio and video data is intermingled. That said, clearly, there's a way to parse the audio out of the stream...but also wonder how that impacts the need to clock the audio with connected devices/software.

    Originally Posted by pandy View Post

    And apologies for all mistakes - to be honest as HDMI standard is payed i lost will while ago to follow all this crap so my information are based on pre 2.0 HDMI (but i doubt that they introduced radically new way of HDMI with 2.0)
    No worries! I appreciate your thoughts. FWIW, apparently, HDMI 2.0 (and 2.1 in particular) has made huge leaps in bandwidth...

    LINK: "Thanks to the vastly increased bandwidth of HDMI 2.1, eARC can handle 32 channels of uncompressed audio, or up to 8 channels of 24-bit/192kHz audio."

    However, it seems it may be an unrealized potential thus far.
    Last edited by Muon; 14th Jan 2022 at 18:41.
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  7. Originally Posted by Cornucopia View Post
    I am wowed by your gear, and think your attempt is cool, but I expect it will lead to a dead end. Plus, you are putting a lot of effort into trying to stuff 2 systems into 1. Maybe leave it as 2 parallel systems - then you could try multiple AVRs, or a mixer board w 12 outs going analog to 12 ins directly to power amps.


    Scott
    Thx for the reply..Haha, yes, it's a lot of effort for potentially no return. When first considering options for how to design this space a few short weeks ago, I knew next to nothing about these aspects of AV. But in my mind, I was like "There's gotta be a way to connect these dots", and maybe there currently isn't. But every rabbit hole I went down helped me understand the whole space a little better, so I've been appreciating the journey just from a learning perspective.

    Short of stumbling upon some sort of breakthrough, I will probably settle for a Home Theater-only setup in the shorter term. But I will probably go ahead and use reference monitors for speakers and cross the bridge of integrating DAW monitoring at a later time BC I don't really have the budget to build out the computer side of the "parallel". That money is better spent outfitting my main mix space. But could very likely end up with a setup similar to what you describe in due time (esp BC it seems it may be the only way to do it, currently anyway).

    That said, extra expense aside, there would be so many advantages to a more integrated system, from less clutter to enhanced QC potential. And I've discovered so many esoteric little details about what may be on the horizon, technologically speaking, a way to do what I'm asking about may very present itself. If folks are interested, I can post a little summary of what I've learned.
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  8. Originally Posted by Muon View Post

    No worries! I appreciate your thoughts. FWIW, apparently, HDMI 2.0 (and 2.1 in particular) has made huge leaps in bandwidth...

    LINK: "Thanks to the vastly increased bandwidth of HDMI 2.1, eARC can handle 32 channels of uncompressed audio, or up to 8 channels of 24-bit/192kHz audio."

    However, it seems it may be an unrealized potential thus far.
    Audio bandwidth is fraction when compared to the HDMI and video - 12 channels should be fine with HDMI 1.4, perhaps even 1.3 (TMDS pixel clock is almost 300MHz)

    ARC is other type of functionality (signal flow from sink not source i.e. reverse direction)...

    Checked briefly HDMI 1.4 specification ( https://www.youtube.com/watch?v=aGuNsiSZ9RI ) - HDMI provide two ways for transmitting audio - first as regular Audio Sample Packet where audio up to 6.144Mbps is supported and second way trough HBR Audio Stream Packet where audio with higher than 6.144Mbps speed can be transmitted however HDMI specification depends highly on IEC 60958/IEC 61937 and CEA-861-* (where * is letter and means version, higher better from your perspective and CEA-861 is primary standard for HDMI - HDMI is a form of extension of the CEA-861-*).

    All those standard are paid so you can try to dig or older illegal versions or buy newer legal version of standards - i don't like this and as such my reluctance to HDMI - you can start from HDMI specification then search for CEA-861 and finally very old IEC 60958 and slightly newer IEC 61937 where all this is defined.

    My impression is that for HDMI this is not an issue to carry 12 or even more audio PCM channels - but as always issue will be source and sink capability (software) - IMHO you should consider FPGA approach, search for some HDMI reception capable FPGA development board, hire some FPGA guy (Easter Europe/former soviet block guys are good and relatively cheap), buy HDMI receiver core (or use fixed HW reception HDMI - depends on your development board) and process PCM in digital domain (extraction from HDMI, peak level reporting, SPDIF/I2S audio out to external DAC's) - overall cost should be around 10k USD - other issue will be source side - not sure what is your HDMI source (you may consider similar - FPGA approach)...

    You can find HDMI open cores... ( first shot example https://github.com/arunchaudhary123/FPGA-DESIGN-HDMI ) so perhaps price can be lower...

    Good luck!

    Btw - perhaps using USB (TB? - no clue as all my Mac's are pre PowerPC) can be option for you - then everything should be simpler. Tricky part will be synchronization between audio/video but this can be relatively easier to solve...
    Last edited by pandy; 15th Jan 2022 at 12:28.
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