You can get HDMI extractors that output 8 channel I2S: https://www.aliexpress.com/item/33031920347.html
The problem is that you can't easily convert that to 8 channel AES. (In my case I'd like it converted into a single ADAT line, but that seems even less possible.)
It's funny how it's so easy to get digital stereo audio from HDMI to a sound card, but it you want multichannel it's like 100x the price.
The problem is that you can't easily convert that to 8 channel AES. (In my case I'd like it converted into a single ADAT line, but that seems even less possible.)
It's funny how it's so easy to get digital stereo audio from HDMI to a sound card, but it you want multichannel it's like 100x the price.
I bought the extractor that I linked above, and while I didn't get it working for multichannel, it's nice to have a SPDIF extractor that can run off HDMI power alone.
Anyway, I recently attempted to buy a MOTU HDX-SDI Thunderbolt for monitoring and potentially capturing multichannel HDMI audio, but there were three pretty big problems: 1) You need to have it connected to a Mac/PC to use it at all, 2) It doesn't pass HDMI (or any other) audio directly to its outputs, and 3) There have been no driver updates in eight years, and it's 100% unusable on any MacOS after 10.9. I looked into hacky workarounds for quite a while, but there's nothing. I had to return it; hopefully I can get what I paid to customs back as well.
So I'm probably going to do AJA HA5 HDMI to SDI > Blackmagic SDI to Audio > some kind of AES to ADAT, (there seem to be a few).
Anyway, I recently attempted to buy a MOTU HDX-SDI Thunderbolt for monitoring and potentially capturing multichannel HDMI audio, but there were three pretty big problems: 1) You need to have it connected to a Mac/PC to use it at all, 2) It doesn't pass HDMI (or any other) audio directly to its outputs, and 3) There have been no driver updates in eight years, and it's 100% unusable on any MacOS after 10.9. I looked into hacky workarounds for quite a while, but there's nothing. I had to return it; hopefully I can get what I paid to customs back as well.
So I'm probably going to do AJA HA5 HDMI to SDI > Blackmagic SDI to Audio > some kind of AES to ADAT, (there seem to be a few).
Mostly for modern-ish game consoles; maybe Apple TV as well. I'm planning on using an HDMI audio extractor will a 720p "audio only" port to get around the SDI specs. (The one I ordered: https://www.aliexpress.com/item/1005003329676348.html)
I decided to take a chance with a different MOTU device, the V4HD, instead of getting separate converters, since it can route audio inputs and outputs in hardware, and without needing to be connected to a PC.
I decided to take a chance with a different MOTU device, the V4HD, instead of getting separate converters, since it can route audio inputs and outputs in hardware, and without needing to be connected to a PC.
Hi @InspectorGadget. I'm testing one of these with an 8Ch DAC for a 4way stereo x-over using PulseAudio X-Over Rack. It's streaming 8ch to my DAC (seemingly flawlessly) via i2s. This board has no DAC / ADC on it so how (and why) would it do this conversion?
I cant say for this specifically, but many SOCs have built in ADCs and DACs, so it may not be immediately obvious. as to why? because to do it the right way involves expensive licensing and that kind (actually ANY kind) of licensing prevents the use of such chips. you simply could not supply a card that was licensed at these costs and even if you could, its against the licensing agreement of any of the chips that could do it, to provide/expose multichannel i2s/LPCM/DSD/spdif (basically any digital, that would include SDI) outputs from an HDMI input. You wont find them from anywhere other than Asia, as the legality is at best on the grey area.
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I think these chips have all the "correct" lincensing, and also they are probably breaking all of them also...
The board have the chips all acid etched so you can tell which serial number is it.
Also, it probably has a ton of jitter, but I don't have the means to test it.
I have the board, so If someone wants me to check something, let me know.
This digital to analog to digital theory sounds a bit complicated. They'd need both 8 channel DACs and ADCs. Is this based off of an analysis someone has done?
In any case, I think it would be borderline impossible to sue any given Chinese based seller on Aliexpress over licensing. There's intellectual property theft going on everywhere on that site.
In any case, I think it would be borderline impossible to sue any given Chinese based seller on Aliexpress over licensing. There's intellectual property theft going on everywhere on that site.
The chip looks a lot like an Analog Devices ADV7511 or similar, which AFAIK it's an all digital chipset.
Anyways, I guess this is not a hifi device...
Yes its complicated, but its still cheaper and that is why they do it. Nothing the suppliers of such cheap boards do is about quality. No license for purchasing the chips allows this to happen and as mentioned the cost of them in the first place would not allow a price like these things are priced.. any digital outputs supplied much be encoded/not exposed. Anyway its been a while since I looked into this and dont have the time right now. maybe things have changed. i'll update tonight
Interesting. I've never tried sending audio from a 7.1 video source to my DAC. (something to try this weekend).
I'm taking a stereo audio source (FLAC, WAV, mp3, live input via Pulse loopback, etc), sending it to a virtual input of PulseAudio crossover rack, which divides frequencies and sends out to 8Ch DAC via the HDMI bus.... I wonder if, in the event that the source is an encoded 7.1 movie it would simply forward that same encoded information to the i2s channels, to be decoded downstream (so not their problem)
@mga2009 Interested to hear your findings if you do figure out how to measure
I'm taking a stereo audio source (FLAC, WAV, mp3, live input via Pulse loopback, etc), sending it to a virtual input of PulseAudio crossover rack, which divides frequencies and sends out to 8Ch DAC via the HDMI bus.... I wonder if, in the event that the source is an encoded 7.1 movie it would simply forward that same encoded information to the i2s channels, to be decoded downstream (so not their problem)
@mga2009 Interested to hear your findings if you do figure out how to measure
No. i'm guessing your HDMI->8 channel dac connection is i2s over HDMI interface, there is no HDMI signal, or video/audio decoder involved in this transfer. It is simply leveraging the HDMI connector/cable and driver hardware to send i2s.
I'm testing this board which is receiving HDMI (audio & video) from my Raspberry Pi using standard 7.1 A/V HDMI protocol. Not just i2s audio over the physical HDMI interface.
Indeed, the DAC is only leveraging the audio related pins (bck, lrck & data's 0-3) to extract audio-only from the HDMI/i2S board.
So I guess what I'm (hoping) is, that if the source is simply stereo PCM and there's nothing to decode, the extractor just sends that same PCM data to the i2s but without any compression, decoding DAC/ADC etc.
Yeah, i'd be interested to see if it is really extracting 8 ch i2s from hdmi, rather than just taking the 2 channels PCM and converting it to 8. Is it seen as an 8 ch audio card by the rpi, or any computer with HDMI? I guess thats the rub, it will extract 8 x PCM from something that is decoded, but not an actual interface. Intrigued though, as its the first ive seen of these that appears to be confirmed to do 8 x 192khz PCM output.