HDMI output from PC.

[Dave Plowman (News]

Before I start chasing things - ie RTFM - should the HDMI feed from a graphics card also be capable of carrying system audio? On Win10, if it helps.

[jon]

For digital audio, if an HDMI device has audio, it is required to implement the baseline format: stereo (uncompressed) PCM. ... With version

1.3, HDMI allows lossless compressed audio streams Dolby TrueHD and DTS-HD Master Audio. As with the Y?CBCR video, audio capability is optional.

[Andy Burns]

Yes, but it'll show up as a different output device from your analogue output, but any worthwhile program should let you choose

[John Rumm]

Yes. It will add an additional audio output device to the machine. So when you look at the volume control in windows there will be a gadget at the top to let you select the desired output device.

[Paul]

If you put your mind to it, you can come up with a way to be holding an HDMI connector in hand, which has no audio.

But normally, up to 8 channel LPCM can be carried. And LPCM (linear pulse code modulation), is just straight samples, with no A-law, u-law, or compression scheme. There is plenty of bandwidth on HDMI, so it's not pinched for bandwidth like SPDIF was.

Video cards generally come in three generations. For the longest while, there was no audio at all, associated with video cards.

The first video card with sound, actually relied on the user running the SPDIF signal from the sound chip on the motherboard, over to a connector on the top edge of the NVidia video card.

Then, and only then, did some flavor of digital audio go across HDMI. It's possible DisplayPort didn't even exist yet. Since SPDIF had limited bandwidth, you would not expect to be running 8 channel LPCM with that generation of hardware. SPDIF is 2 or 4 channel, with 4 channel being, um, nonexistent. And running AC3 would ruin the effect (it's compressed).

The era today, the "CODEC" if you will, is on the video card. It no longer relies on SPDIF passthru as a mechanism. And more audio channels are available as a result. The logic block that does it, might be considered HDAudio of some sort. Or maybe it declares itself that way.

AMD chose a different route to get audio on theirs. The driver package (the jumbo video driver), had a RealTek folder on it, and the suspicion was, that AMD had bought an intellectual property block from RealTek, to implement the HDAudio function. It's not clear today, whether they're using an in-house design and have dumped the RealTek interim solution. AMD is also rumored to have bought a USB3 block for their Southbridge, rather than design their own. These are time savers and mean hiring fewer "specialists" to make stuff.

*******

HDMI 1.0 December 2002 8-channels of 192kHz/24-bit audio (PCM)

HDMI 1.1 May 2004 + high resolution audio format???

HDMI 1.2 August 2005 + DSD (Direct Stream Digital), + Super Audio CD (SACD)

HDMI 1.2 December 2005

HDMI 1.3 June 2006 + native Dolby TrueHD and DTS-HD Master Audio streams for external decoding by AV receivers

HDMI 1.3a November 2006 ... HDMI 2.0 September 2013 + Up to 32 audio channels Up to 1536kHz audio sample frequency

Just because the standards say this, does not mean the computer industry immediately implemented this "with haste". The passthru SPDIF idea was particularly egregeous (it smacked of "we don't give a f*ck"). I'm not aware of anyone wiring that up, so I don't even know if it works (that's because the SPDIF output from sound chips, is TTL level and not cable level, and the signal might not be standardized well enough to be connecting it up!). But once the video card got the onboard CODEC, that's when people started using it.

You can start by checking whether a suitable "digital audio" item is in the playback choices in Windows. I have some with the word "NVidia" on mine. But no equipment to test with (no fancy monitors or TV sets). The video card was purchased for OpenCL or CUDA compatibility, and for the video SIP block (video encoder). I tried cracking a password on the video card, but the software said it would "take 13 years" :-)

Paul

[Michael Chare]

If not working, I would go to Control Panel/Sound and check that the HDMI output is selected.

[Dave Plowman (News]

Thanks for the excellent explanation Paul. An HDMI cable from my laptop to the TV carries audio just fine. But with the desktop here, it's not so easy to try without moving TVs around. But it is a new and pricey MB and graphics card so you've given me the hope to actually try it. The laptop does identify the TV as a selectable sound output in the windows settings.

[Fredxx]

Being recent I would have thought the card should produce good audio. Most HDMI ICs I have come across have audio and I guess the same should be the case for a PCIe card.

Can you provide the make and model for the card?

Quite often the drivers shipped with windows are a subset of what you can get from the board manufacturer. If you don't see audio output device in Device Manager (with a suitable monitor attached, i.e. one that can take audio[1]) then the appropriate drivers are not installed.

[1] Monitor's video details are provided in EDID through a DDC channel. You can use: think that this is also how audio details are conveyed to the host system.

[Andy Burns]

There's no analogue audio circuitry involved, the graphics card just has to insert audio data packets into "data islands" during blanking periods

[Fredxx]

Quite, the digital serial stream has to come from somewhere.

It all depends on what you call "audio circuitry" which in this case would be LVDS drivers within the HDMI IC, a couple of tracks and some protection against ESD.

[Paul]

There isn't usually outboard converters on GPUs.

Even though, yes, there are Silicon Image chips for such purposes, which have reclocking options giving x1 pixel resolution capability (don't need to follow the divisible by 8, divisible by 2 rule), those are not typically used.

Some of the output buses on the video card, are reconfigurable. Some are not. There is usually an LVDS bus, but that sort of thing hasn't been used in some time on desktop video. Perhaps back in the dual lane DVI era, there was the odd video card that used an outboard device to add capability. But so many designs follow the NVidia reference design, that anything like this is a low runner. There was some kind of general purpose parallel bus, but I don't remember the name of that bus which connects to external converters.

The GPU is, most of the time, direct drive, and the only things you need on outputs, are ESD protection solutions, capacitive coupling with ceramic caps or whatever. Now, this design, the SMPS is on the wrong side, but you don't really see any LSI between the GPU and the front connectors.

To keep software happy, there'd be a bus master so the HDAudio bus could exist (inside the GPU, can't see or touch it). That will have a DMA block associated with it, so HDAudio FIFO gueues can be kept filled, and fed to the serial bus the HDAudio uses. Then, the HDAudio codec block, with registers, hooks to that. Then, the ADC and DAC are stripped off, and the output is pure digital. The analog part of the mixed analog-digital design is removed. Then there'd be the GPU crossbar, where all the digital goodies are mixed and output. What is this in aid of ? If you look in the hardware info, there should be an HDAudio "bus number". The motherboard HDAudio chip would be like "Bus 1" and the video card block shown here, would be "Bus 2", and it's the serial high speed interface which is the bus being enumerated. NVidia could extract the HDAudio bus master block, from one of their Southbridge projects and reuse it.

XBAR serialHS <=== Mix to ---- HDAudio --------- HDAudio bus master block <--- DMA buffer fill LCD HDMI Codec via PCIe Mon via TSI minus DACs

TSI = time slot interchanger (shorthand for digital insertion in fixed pattern) XBAR = crossbar for same purpose (digital routing of display channel to connector) DAC = Digital to analog convert (as seen on motherboard HDAudio chips) Bus Master Block = what a Southbridge would use, to drive an HDAudio codec 48 pin chip DMA = direct memory access, which pulls buffers of audio data to keep the FIFO feeding the HDAudio bus filled. Repeating sound effects heard, if this ever crashes (in a game, you can hear the FIFO replayed over and over again).

( This isn't current generation, but it's one of the few crossbar diagrams I have to offer. Page 8, and be patient, as it can take Acrobat Reader 20 seconds to render the diagram on the bottom of Pg.8)

Somewhere in the ROM onboard the video card, is a declaration (that the driver reads), as to what wiring is doing what feature. I don't know any of the details of that. Like if three of five outputs are available on the faceplate, something has to know the other two are No Connects.

A laptop GPU is slightly different, in that an LVDS bus goes direct to the panel, has no Plug and Play information, and the PNP has to be "faked". If you buy a laptop which has low-res and high-res panel options, you crack your panel, then buy the wrong replacement LCD, there will be black bars on two sides of the displayed image. And that's because the laptop doesn't know which panel is connected, and the information is being faked. And to fix that, you would have to figure out which bit needs updating, so that the fake declaration matches the panel dimensions. The other buses on the laptop GPU (single VGA or HDMI output), they would come direct from the GPU as appropriate. As TMDS bus, for the HDMI.

There is a rich collection of converter devices, for TV sets, and some of the whizzy gadgets we use, have been re-purposed digital components from TV sets. And there's a subset of components (ones with HDCP capability), that are restricted and not for sale to punters and the datasheets are NDA only. On the BlackMagic HDMI capture card, the first card, there are three Analog Devices front ends that could be fitted to the design, and only the non-HDCP version has info. The others are hidden from view. And each had differences in the analog capture features too. This is how some Chinese designs slipped out, which functioned as HDCP strippers, and those were stopped at the border by US Customs after it was figured out. By reusing things that could function as HDCP strippers.

But as far as the parts bin for video cards, a metric ton of SMPS components and designs, a ROM for declaration and read-in by the BIOS at startup, ESD protection components, most of the heavy lifting is done by the GPU itself. This keeps down the BOM cost. The most wasteful part, is the SMPS (the Volterra stuff on high end designs). When you want 1V @ 200A, who ya gonna call. Oh, and we can't forget the VRAM.

Paul

[Andy Burns]

But it shares those pins/tracks with video data, there aren't separate ones for audio, so other than timing when to send audio rather than send video, it doesn't take much.

[Brian Gaff (Sofa]

Yes it bloody does, in fact stopping the darned thing is my biggest nightmare. I had to use a vga to hdmi in the end to keep the audio going via the sound card I wanted it to when the input was selected on my Samsung TV.

Brian

[Brian Gaff (Sofa]

Its a pain though as you cannot seem to over ride it at all. Windows 7. Brian

[Paul]

There's a control for setting where the output goes, whether HDMI digital audio, sound chip SPDIF digital, or sound chip analog audio. Each output has a name.

There's a tendency for the wrong thing to be selected, if changing drivers, or, right after the OS gets installed. You just change it to suit the situation.

The most evil situation I've run into, is installing two sound cards, one driver had a bad registry setting behavior, and damaged a shared setting -- both sound cards then failed to work. That was on Windows XP. I haven't had that happen in other situations, but that's because my collection of junk sound cards is retired. The onboard HDAudio is sufficient.

Paul

[Dave Plowman (News]

Surely you could do this in software? Most progs give you the choice of selecting audio in and out?

[Steve Walker]

The worst I had was also back in the days of XP. A new motherboard, with onboard sound that didn't work. Replacing the motherboard didn't help. I ended up disabling the onboard sound and plugging in a sound card - which irritated me, because the onboard sound still showed up as present.

It was more than a year later that I discovered the source of the problem, corrected it and switched to using the onboard sound - by downloading a new driver ... for my *NON*-sound equipped *VIDEO* card!

[Dave Plowman (News]

Bit more info.

DVI to HDMI lead direct from PC graphic card DVI output to TV works fine. This adaptor - DVI-D to HDMI + USB to add sound, no picture. PC does recognise the adaptor USB connection in device manager, so I'd guess it is getting power.

[Dave Plowman (News]

Contacted the seller, but I'd guess they are just a box shifter, and all they could help with was a return for re-fund.

[Theo]

What's the model number of the adapter, OOI?

Theo