Bitstream via HDMI from nVidia or AMD GPUs

miggyboys

Hi all!

Q. Has anyone managed to bitstream their audio via HDMI from their graphics card?

I'd like an external device to decode all sound from my PC (either an AV receiver or soundbar, both can decode all the common sound formats up to Dolby TrueHD and DTS-HD MA).

I received an email from nVidia today to state that my graphics card (nVidia GForce GTX 1060 6GB) only outputs sound in PCM. I've asked them if any of their GPUs allow audio to be output in bitstream. I'd happily move to AMD if the RX 580 / Vega 56 did allow bitstream.

If anyone wants to ask why I want to do this, it's because quality external devices that have good DACs inside and that are connected to good speakers are far superior at producing sound than PC components.

Thanks for your answers in advance!

andy1249

Yes.
Its been possible to bitstream hd audio codecs from a PC for years, from just about any PC with a HDMI port.
The last time this used to be an issue was back in 2010 sometime.

Is there something unusual you are trying to do?
Otherwise its just a case of the playback software, i.e. Plex, Kodi etc. being set to bitstream.

miggyboys

Not really, others must surely have tried what I am doing with AV receivers. I understand there are some software applications that enable bitstream - would Plex, Kodi etc enable bitstream with my GPU even though nVidia say the card cannot output bitstream, only PCM via HDMI?

Here's my setup:

PC with nVidia GTX 1060 6GB GPU - HDMI out - Yamaha YSP-2200 soundbar.

Whatever I'm playing/listening to/watching, I would like all the sound by default to be bitstreamed out to the soundbar.

andy1249

Should not be a problem.

Which HDMI audio formats do NVIDIA GPUs support? | NVIDIA

Note that where content has the audio in a codec package , such as dolby digital, DTS , Dolby tru HD , or DTS MA HD your choice will be to either have the card decode to PCM or to “ bitstream”  that codec package to a receiver for decoding.
That is very specifically what bitstreaming means.
Obviously your receiver must be able to support the format being bitstreamed.

Where the content is already PCM ( not in a package ) then PCM is output.
The card will bitstream where bitstreaming applies.
You cannot “ bitstream “ everything.

EndlessWaves

Decoding isn't anything to do with a DAC.

Decoding is uncompressing the data from a format like TrueHD into an format that can easily be manipulated (played back etc.). It's digital all the way through, the creation of the electrical signal that drives the speakers (aka analogue) is always done at your external device whether you bitstream or not.

The main reason to bitstream used to be that the receiving devices often offered different options or treated the sound differently depending on format.

If you've already got the hardware it's worth a go, it certainly used to be supported by everything. nVidia might have removed it as no longer worth maintaining, but you don't tend to hear about removed features. It does seem a bit early though.

miggyboys

Hi andy1249

I've had it confirmed unfortunately. Nvidia GPUs cannot bitstream audio. They only output in PCM. Perhaps there is a third party application that forces the change permanently across the whole PC. There is no option in the Nvidia control panel that allows one to change between PCM and bitstream.

Nvidia also confirmed this yesterday via email: 'There is no Nvidia GPU that supports bitstream'.

I'm still interested in hearing if anyone has circumnavigated this though.

miggyboys

Hi EndlessWaves

Thanks for correcting me and explaining the audio path. I've tried it but I can only PCM out from HDMI to my Yamaha YSP-2200 sound bar and it sounds truly awful. I've read that it doesn't matter where the DTS-HD MA / Dolby TrueHD conversion takes place (from compressed PCM to decompressed) and it shouldn't make a difference if this decompression takes place in the source device or external device. What matters is where the DAC takes place. I don't know if the bit about PCM decompression is true, I would have thought that any such decompression is always best done in the better quality devices one has in their setup. But as I said, it sounds awful.

andy1249

Ive been bitstreaming from nvidia cards for years and still am.
Im using a HTPC , and the Nvidia Shield .... if the shield couldn't bitstream you,d know about it due to the uproar it would cause.

Bitstreaming mostly applies to watching movies/tv shows that have dolby or dts codecs.
For this you need playback software that supports bitstreaming , Kodi , Plex etc.

Controls for bitstreaming are not found in the graphics card utilities. They are found in the playback software of your choice.

As per the table I posted you have been able to bitstream for years , since the 6xx cards or approx 2010 or earlier.

Im not sure how you had it confirmed or the specific question you asked , if you asked can you bitstream without third party playback software then certainly the answer would be no.
But the hardware is definitely capable of it , you just need playback software that uses it.

Edit: What content are you playing and what is your playback software. Then I can be specific in advising what you need to do.

EndlessWaves

For a lossless encoding like TrueHD you end up with exactly the same data you started with wherever you decode it. That's the definition of lossless. If you're ending up with different sound it's because some link in the chain has decided to treat it differently based on format rather than because of any difference in the audio data.

I'm not sure how lossy encodings work for audio. Whether reconstruction is needed (as it is for video) and if so whether it's completely specified in the format standard documents or whether some element is subjective.

PCM can be considered an encoding like TrueHD but it is a very simple one with no compression at all, so it is widely used for digital transmision and manipulation of audio data. For example .wav files are PCM.


In terms of practical suggestions, does your playback software support exclusive mode for a sound device? That'll let it take exclusive control of that output and not have the audio of other programs mixed in. It's required for bitstreaming, but it can also be used on it's own.

It's sometimes referred to as WASAPI after the windows library that first introduced the functionality.

miggyboys

Hi andy1249

What you say is encouraging and music to my ears. An Nvidia 2nd line support technician confirmed via their support help desk about their not being able to bitstream after I logged a query with them about it. It would have been useful if they told me that their hardware is enabled but their control panel doesn't support it though some third party applications do. I suppose they don't want to acknowledge it, because then they've got to support queries via their help desk which means more work for them. It would make it a lot easier for everyone if they had it as a default option, it's their hardware after all.

I'll install Jriver and PowerDVD to test the bitstream options. I play MKV files for films using VLC but I'm more bothered about gaming which is more problematic. I don't remember seeing bitstream options for audio in any of the games I play, though admittedly, I've never looked for it either. Games I've played are Crysis 3, The Witcher 3 and MAME.

I also watch some Netflix and Youtube videos. My ideal goal would be to have all audio bitstreamed by default, irrelevant of what I'm watching or playing but it seems this isn't possible and it's all currently application enabled.

Thanks for your help.