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how to extact audio from "display port"

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  how to extact audio from "display port" hput <hputn3@zohomail.com> - 2022-06-28 16:17 -0400
    Re: how to extact audio from "display port" Paul <nospam@needed.invalid> - 2022-06-28 17:45 -0400
    Re: how to extact audio from "display port" not@telling.you.invalid (Computer Nerd Kev) - 2022-06-29 07:51 +1000
      Re: how to extact audio from "display port" Paul <nospam@needed.invalid> - 2022-06-28 20:34 -0400
        Re: how to extact audio from "display port" Computer Nerd Kev <not@telling.you.invalid> - 2022-06-29 11:12 +1000

#13923 — how to extact audio from "display port"

I'm soon to have a computer with a video card that outputs only thru
a "display port".

Of course I can run an extended rca mini jack from the computers sound
plug in back.

But in the long run:

There must be some way to separate the audio and video on a
"display port" output?  I know they have adapters from "Display port"
to hdmi.

But having no luck googling up a tool that splits the audio signal out
of display port..

Can anyone suggest something that might help?

Also, am I wrong in thinking that the sound quality at the sound card
(a Quadro M4000 8GB) "Display port" will be superior to the sound at
the rca mini port in back?

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#13924

On 6/28/2022 4:17 PM, hput wrote:
> I'm soon to have a computer with a video card that outputs only thru
> a "display port".
> 
> Of course I can run an extended rca mini jack from the computers sound
> plug in back.
> 
> But in the long run:
> 
> There must be some way to separate the audio and video on a
> "display port" output?  I know they have adapters from "Display port"
> to hdmi.
> 
> But having no luck googling up a tool that splits the audio signal out
> of display port..
> 
> Can anyone suggest something that might help?
> 
> Also, am I wrong in thinking that the sound quality at the sound card
> (a Quadro M4000 8GB) "Display port" will be superior to the sound at
> the rca mini port in back?
> 

They make the following kinds of adapters. I only have the first one.
I would hope the computer only routes sound to video connectors that
are in usage. If your video card had three connectors, it's not necessarily
the case that all three have the same audio signal at the same time. But
I haven't tested this. That would require me to buy more of these.

    HDMI --- (box) ------- VGA
                   ------- Stereo Audio
                   ------- (some do SPDIF, but that's a different product)

      DP --- (box) ------- VGA
                   ------- Stereo Audio

These can also be equipped with a miniUSB
solely for +5V power. Even though the video card
DP and video card HDMI have 5V power pins on the
connectors. My video card provides enough power, that
any of the adapters I've tried, they worked.

Some equipment in your AV rack, could have poor +5V on one
of those display connectors, and that's why the adapter has
an additional (optional) +5V input.

Things like soundbars can do audio-drop to run their speakers,
then pass an HDMI-out to a TV set. This allows the soundbar to
have audio and the TV to have video.

Generally, I don't recommend buying roomfuls of toys of
this nature. Test the kit you bought first, and see if it is
satisfactory. Maybe you have enough goods right now to get
the job done. Maybe the motherboard audio is "good enough".

Adapters could range from $30 to several hundred (for Apple docks)
that do conversions. Some of the adapters could be more expensive
than the video card they're connected to.

Sound cards vary a bit on background noise level. A Creative
with a shield box around it, might be -108db. Computer sound (HDAudio)
could be -70db. The worst part of computer sound, is when you move the
mouse and "digital noises" can be heard in your speakers. Concert hall
music can have sufficient dynamic range, to need a clean noise floor.
Many other kinds of music don't really need to be all that clean.
But things like mouse-noises, those suck. Sometimes you get stuff
like that from a grounding problem in the computer room.

These are moments when you start retrofitting stuff.

I haven't seen any HDMI to four 1/8" connectors for 7.1 sound. HDMI
and DP should at a minimum support 8 channel LPCM (linear pulse code
modulation), which is the "patent-free" audio format on video. There
are various Dolby options no one cares about. A sound bar might pick
off 5.1 and drive its own Sub (as your DVDs might have a 5.1 audio track).

Your new motherboard might also have TOSLink, which is SPDIF sent
via red LED light. Which is fine if you have an AV receiver with
a TOSLink input. Otherwise (like for me), the TOSLink is a waste
of time. My amp is one I built myself and there's no TOSLink on it :-)

You could send audio over Bluetooth... but... don't do that.
It's pretty awful. It's like listening to the lowest bit rate MP3.

There is a software product, RightMark Audio, that can be used to
test computer sound. I'm not recommending a copy, just look
for a reviewer that uses it and see what it can show. SO if you
were interested in some Creative soundcard, you could combine the
search term "RightMark" and get some graphs.

    Paul

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#13925

hput <hputn3@zohomail.com> wrote:
> There must be some way to separate the audio and video on a
> "display port" output?  I know they have adapters from "Display port"
> to hdmi.
> 
> But having no luck googling up a tool that splits the audio signal out
> of display port..

HDMI and DisplayPort are both entirely digital standards, so in
neither case is there a conventional audio signal at the port. It's
just digital signals basically like those feeding into the sound
card/onboard-chip in the computer, so you effectively need another
sound card like device to plug in to the DisplayPort and supply
an analogue audio output.

> Can anyone suggest something that might help?

I haven't seen such a device myself, but they probably exist. Maybe
adapters to VGA etc. with audio output built-in will be cheaper,
though they'll likely be poor quality.

> Also, am I wrong in thinking that the sound quality at the sound card
> (a Quadro M4000 8GB) "Display port" will be superior to the sound at
> the rca mini port in back?

Seeing as the former is digital, they're not comparable. In
practice it would depend on the quality of the sound
card/onboard-chip in your computer compared to whatever device you
plug into the DisplayPort which does the same job.

-- 
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#13926

On 6/28/2022 5:51 PM, Computer Nerd Kev wrote:
> hput <hputn3@zohomail.com> wrote:
>> There must be some way to separate the audio and video on a
>> "display port" output?  I know they have adapters from "Display port"
>> to hdmi.
>>
>> But having no luck googling up a tool that splits the audio signal out
>> of display port..
> 
> HDMI and DisplayPort are both entirely digital standards, so in
> neither case is there a conventional audio signal at the port. It's
> just digital signals basically like those feeding into the sound
> card/onboard-chip in the computer, so you effectively need another
> sound card like device to plug in to the DisplayPort and supply
> an analogue audio output.
> 
>> Can anyone suggest something that might help?
> 
> I haven't seen such a device myself, but they probably exist. Maybe
> adapters to VGA etc. with audio output built-in will be cheaper,
> though they'll likely be poor quality.
> 
>> Also, am I wrong in thinking that the sound quality at the sound card
>> (a Quadro M4000 8GB) "Display port" will be superior to the sound at
>> the rca mini port in back?
> 
> Seeing as the former is digital, they're not comparable. In
> practice it would depend on the quality of the sound
> card/onboard-chip in your computer compared to whatever device you
> plug into the DisplayPort which does the same job.
> 

The DisplayPort 8ch LPCM and the HDMI 8ch LPCM, are digital
from end to end and no degradation is present. You stuff the
digital samples into the interleaved stream in the DP output.

The sound is only as good as the source.

It is when the 8ch LPCM is converted to analog with a DAC,
that the degradation occurs.

This assumes nothing is going on, such as a previous scam
where a 24 bit digital audio standard, some of the manufacturers
were setting the 8 least significant bits to 0 permanently,
causing the audio actually sent to be 16 bit audio. So stupid
stuff has happened in the past, but I haven't heard of this
happening with the present day stuff.

There was at least one adapter or dock, that had SPDIF
as an output. Which would give you stereo with 24 bit accuracy.
The SPDIF is converted back to analog, inside the AV Receiver/Amp.

"HDMI to VGA + Optical Toslink SPDIF + 3.5mm Stereo Audio Converter Support 1080P"
https://www.amazon.ca/Security-01-Optical-Toslink-Converter-Support/dp/B01FVFWMAY

You can also convert VGA back into HDMI, but this is a bad idea.
Only mentioned for completeness. There should be HDMI to HDMI+Audio,
as that's the sort of thing soundbars use.

    Paul

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#13927

Paul <nospam@needed.invalid> wrote:
> On 6/28/2022 5:51 PM, Computer Nerd Kev wrote:
>> hput <hputn3@zohomail.com> wrote:
>>> Also, am I wrong in thinking that the sound quality at the sound card
>>> (a Quadro M4000 8GB) "Display port" will be superior to the sound at
>>> the rca mini port in back?
>> 
>> Seeing as the former is digital, they're not comparable. In
>> practice it would depend on the quality of the sound
>> card/onboard-chip in your computer compared to whatever device you
>> plug into the DisplayPort which does the same job.
> 
> The DisplayPort 8ch LPCM and the HDMI 8ch LPCM, are digital
> from end to end and no degradation is present. You stuff the
> digital samples into the interleaved stream in the DP output.
> 
> The sound is only as good as the source.
> 
> It is when the 8ch LPCM is converted to analog with a DAC,
> that the degradation occurs.

Yes, including any noise that the analogue signal picks up while
going down a long cable after leaving the DAC. But my point was
that without knowing the quality of the DAC feeding that "rca mini
port in back", it's unclear whether using a different DAC connected
to the DP would offer any advantage, and either way the sound
quality will have nothing to do with that Quadro M4000 GPU. The
real issue seems to be an assumption by the OP that the GPU has an
audio DAC built-in, which isn't the case.

-- 
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