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I marked the key problems in case anyone else want to try on Windows 10, which seems hopeless and it's not due to the hardware.

confirmed failures on Windows Server 2019 (compatible to Windows 10 update 1809):

PCM, "listen to this device" works, no delay. Using DirectShow graph with AC3Filter gives a noticeable delay of some sort.

Using "auto" optical sound mode from Samsung TV, sound control shows full volume all the time, and:

DirectShow graph constructed in GraphStudioNext:

AC3filter plays only noise. There is no detector listed in the "Decoder Info" section under "SPDIF" tab. I checked the source code of 1.46 but it only included code for the config interface, not the filter itself...

WDM capturing streaming device which was reported working in others' earlier tests is not listed as a source, but hidden inside the long list of filters. It can be added but cannot be connected to AC3Filter or anything at all.

ffmpeg also fails. The raw data can be captured by:

Code:
ffmpeg -f dshow -i audio="Digital Audio (S/PDIF) (C-Media High Definition Audio Device)" -c copy -f wav test.wav
When played directly, it sounds just like AC3filter.

Neither the "ac3" decoder nor the "spdif" demuxer in ffmpeg can handle the file. The latter gives "Data type 0x0002 in IEC 61937 is not implemented", even through it seems to able to recognize some of headers and gives: "Audio: ac3, 5.1(side), fltp".

I wonder if the audio has been corrupted in some way, given that WDM doesn't work and the input might have been wrongly adjusted for the volume control even if it's set to max.
 

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My last attempt is Sound Blaster X7, which does work but not in the way I hoped.

What it does:

Sound Blaster X7 is not a sound card but a standalone DAC+preamp itself with an USB interface. It can decode Dolby Digital from SPDIF-IN and output from LINE-OUT.

What it doesn't:

It cannot, however, allow you to record or in any way manipulate the sound at software or driver level (e.g. Equalizer APO), because the sound doesn't go through computer. Neither recording nor "listening to this device" works. PCM does work though.

In fact, because it always detects Dolby Digital automatically, you can never get Dolby Digital sound and decode by yourself. The only thing you can do with Dolby Digital is to output it to line out, and change volume plus some SBX tweaks.

Compatibility:

Officially it doesn't support DTS. I don't have any DTS source to verify if recording of DTS encoded in PCM is possible.

I also don't have any audio source with SCMS protection to check for that.

It works for Samsung TV in auto audio format. I guess it should work for all that are listed on 5.1 Surround Sound Passthrough On TVs as long as the TV doesn't try to send DTS.

For a 5.1-only $300 sound card it's not too satisfactory, but that's it...
 

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Hi

Im currently decoding DTSHD, DTS:X, DTS and others, in software, mixing it 7.1, then sending it via PCM for amplification to the home theatre audio system. Why am I doing this and not bitstreaming over HDMI passthrough? Because my LG TV 2020 doesnt support Dolby. Im running eARC and it wont passthrough the TV.

I could be decoding other formats too, meridian packing formats

You know, like Dolby MA and Dolby Atmos, in software, but I dont need too for my use case. The point is, I can, if I needed too.

Given the FFMPEG project has been doing for this a long, long time Im confused as to where all this angst is coming from and why you havent fixed this by now? LAV Filters have very simple configurations panels to enable users to abort bitstream selectively and decode via PCM in software. These free decoders have existed for ages.

The reason SPDIF is dead is not because of some conspiracy around DRM or whatever, its because as an interface for data transport, its grossly lacking in bandwidth. Its dead cos it sucks and cant support what modern content needs to send in real time.

Cheers
 

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Morning, correction to my post, it's DTS the LG 2020 TVs dont accept, Dolby, including Dolby ATMOS is all good.

I'm not running eARC into the HTPC. The chain is HTPC (HDMI 2.0B) most of the time but sometimes its RTX 3xxx so HDMI 2.1 -> LG TV (HDMI 2.1) -> 9.1.4 system (HDMI 2.1) via eARC. eARC on HDMI 2.1 does allot of "auto" stuff, including dealing with latency and bitstream syncing.

I could change it to run eARC and pre-amp duties to decode/split to individual channels for amplification but I don't need to. Theres lots of sources of HDMI In in various cards, commonly capture cards.

My main point is that for years and years decoding both Dolby and DTS in software, including based on free open source software that is publically disclosed, has been the case. And two, SPDIF is dead not due to conspiracy, but is dead because it simply doesnt have the data bandwidth to be useful anymore in transporting digital audio.

cheers
 

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It's only dead because devices aren't sending data of higher bandwidth over it. X7 supports double PCM sample rate for example and ADAT uses the same connection for 8 channels, 24 bits 48K sample rate of uncompressed PCM.

I haven't tried any HDMI capture myself. Seems risky as I don't see any of them listing eARC, and using full HDMI with video passthrough would mean that the card needs to be upgraded for new video formats.
 

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Morning, correction to my post, it's DTS the LG 2020 TVs dont accept, Dolby, including Dolby ATMOS is all good.

I'm not running eARC into the HTPC. The chain is HTPC (HDMI 2.0B) most of the time but sometimes its RTX 3xxx so HDMI 2.1 -> LG TV (HDMI 2.1) -> 9.1.4 system (HDMI 2.1) via eARC. eARC on HDMI 2.1 does allot of "auto" stuff, including dealing with latency and bitstream syncing.

I could change it to run eARC and pre-amp duties to decode/split to individual channels for amplification but I don't need to. Theres lots of sources of HDMI In in various cards, commonly capture cards.

My main point is that for years and years decoding both Dolby and DTS in software, including based on free open source software that is publically disclosed, has been the case. And two, SPDIF is dead not due to conspiracy, but is dead because it simply doesnt have the data bandwidth to be useful anymore in transporting digital audio.

cheers
Hdmi audio HD is a closed format.
I'm not aware of a solution to have an hdmi input on a PC to be able to use an USB DAC.
DAC in AVRs are of a very low quality for the price, same for the amp sections.
So many people trashed their AVR because of a new format / hdmi.
A very good amp should last for 10 years. It is not logical to trash it so frequently.
Separate pre/pro in the HT world have crazy prices and full of useless features ( not so much people really need 11 or 16 channels and dozens of inputs).
An HTC of a few hundreds dollars can decode any audio format (except the object based yet, but you need a lot of loudspeakers to really use it), we now have excellent 8 channels DACs for 1-2000$ on the market.
It is non sense to be obliged to pay 5000$ to get a lower performance pre-pro.
So, HTC as the source sounds the best using media player or even apps, but we still have some sources outside like the fiber set top box, anyway streaming sources are not using lossless formats, they are only using dolby digital. And dolby digital is going through spdif.
Hence, I'm looking for an spdif dolby digital input to decoded 8 channels PCM to an USB attached DAC for the fiber set top box as a source use case.
 

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Hence, I'm looking for an spdif dolby digital input to decoded 8 channels PCM to an USB attached DAC for the fiber set top box as a source use case.
A few key points:

  • SPDIF does not support 8 channel audio.
  • It firstly supports 2 channel uncompressed PCM
  • It secondly supports encoded multi channel in 6 channel audio like Dolby Digital
  • It does not natively support 8 channel like Dolby Digital Plus, it will in fact downgrade DD+ into DD for most consumer implementations or simply not work. It wont pass DD+ natively. Obviously not being able to handle DD+ means lossless stuff like DD TrueHD is also not supported.
  • Your use case is super odd and against the whole ecosystem. Why not use existing, working standards like HDMI? If HDCP annoys you or whatever, use a HDMI device like the HD Fury Vertex range to strip it, fiddle with it etcetc
  • Its just plain false to claim that DD, DTS, DD True HD etcetc cant be decoded and further processed in software, FFMPEG has done it for ages and ages
 

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A few key points:

  • SPDIF does not support 8 channel audio.
  • It firstly supports 2 channel uncompressed PCM
  • It secondly supports encoded multi channel in 6 channel audio like Dolby Digital
  • It does not natively support 8 channel like Dolby Digital Plus, it will in fact downgrade DD+ into DD for most consumer implementations or simply not work. It wont pass DD+ natively. Obviously not being able to handle DD+ means lossless stuff like DD TrueHD is also not supported.
  • Your use case is super odd and against the whole ecosystem. Why not use existing, working standards like HDMI? If HDCP annoys you or whatever, use a HDMI device like the HD Fury Vertex range to strip it, fiddle with it etcetc
  • Its just plain false to claim that DD, DTS, DD True HD etcetc cant be decoded and further processed in software, FFMPEG has done it for ages and ages
I'm not aware of HDMI input for audio extraction, to feed a multi-channel DAC.
HDMI is used only in integrated AVR or pre/pro, hence you are limited to the quality of this segment, which is very poor and very expensive compared to standalone units like DACs and amps.
 

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I'm not aware of HDMI input for audio extraction, to feed a multi-channel DAC.
Capture devices for game console do that: Best Capture Card 2020: Game Capture Devices For Recording and Live Streaming - IGN

None of them seems to support eARC on spec and I don't know if they can do audio-only extraction from HDMI. Since the (useless) video is part of signal, direct support for 4K HDR would be required and those are quite expensive. Some of them also need a Thunderbolt port.
 

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Most game capture devices only capture 2 channel uncompressed audio, likely up to 48khz at 16 bits. You have to remember most of the users stream to sites like twitch, so more than two channel audio isn't necessary and its usually mixed in with audio from the streamer.
 
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