Computers & Electronics

No Audio Through DisplayPort (Dell Optiplex 780 USFF)

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[OP]
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Oct 29, 2002
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No Audio Through DisplayPort (Dell Optiplex 780 USFF)

I purchased a dell OptiPlex 780 from dellrefurbished.ca to use as a htpc, and am having trouble getting audio to the tv.

Here is how I have it set up:
Display port on PC -> display port to hdmi cable -> HDMI port on TV

The video works fine, but I am not getting any audio. Some of the suggestions online are to change the setting for Sound in Control Panel to a different output, but I only see one option.
The sound card uses SoundMax Integrated HD Audio drivers. The drivers, although dated, are the most recent.

Anyone else confront this or have solutions?

FS: Nothing
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Jul 22, 2006
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Display port DOES NOT SUPPORT AUDIO
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Mar 23, 2004
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DP does support audio actually but only multi-PCM (bitstreaming not supported).

When you connect an adapter to a computer's DP you're not really connecting DP at all, if you're using a passive adaper. In this case you are using the D++ functionality (as I like to call it and is indicated by the icon) meaning you should be getting an actual HDMI signal from the card/board, just as if you had plugged into an HDMI port.

If you're using an active adapter though, you are converting a DP signal to HDMI. In this case you have to make sure the adapter supports audio and supports how many channels you need. Again you will only get PCM audio this way and many active adapters are 2.0 only (I have one that's supposed to do up to 7.1 but in reality it doesn't). Note as well that some (particularly older) DP implementations never had audio at all--in that case you won't get audio with an active adapter either.

The [analog] on-board sound is irrelevant. You're interested only in the audio capabilities of the HDMI functionality of the board (in the case of a passive adapter); or the audio capabilities of both the DP and the adapter (in the case of an active adapter).

Note also that in the case that the machine doesn't actually support HDMI-proper, using a passive adapter may just be getting you DVI and not HDMI. So here you will get an image and you may think it's HDMI but it's really just a single-link DVI signal, compatible with HDMI but does not support audio.
[OP]
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Oct 29, 2002
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ES_Revenge wrote: DP does support audio actually but only multi-PCM (bitstreaming not supported).

When you connect an adapter to a computer's DP you're not really connecting DP at all, if you're using a passive adaper. In this case you are using the D++ functionality (as I like to call it and is indicated by the icon) meaning you should be getting an actual HDMI signal from the card/board, just as if you had plugged into an HDMI port.

If you're using an active adapter though, you are converting a DP signal to HDMI. In this case you have to make sure the adapter supports audio and supports how many channels you need. Again you will only get PCM audio this way and many active adapters are 2.0 only (I have one that's supposed to do up to 7.1 but in reality it doesn't). Note as well that some (particularly older) DP implementations never had audio at all--in that case you won't get audio with an active adapter either.

The [analog] on-board sound is irrelevant. You're interested only in the audio capabilities of the HDMI functionality of the board (in the case of a passive adapter); or the audio capabilities of both the DP and the adapter (in the case of an active adapter).

Note also that in the case that the machine doesn't actually support HDMI-proper, using a passive adapter may just be getting you DVI and not HDMI. So here you will get an image and you may think it's HDMI but it's really just a single-link DVI signal, compatible with HDMI but does not support audio.
Thanks for the detailed response. I'm assuming what I have is a passive adapter. I will try an active adapter, but as you've mentioned, that will not guarantee the audio will work.

Anybody with the same computer encounter these issues and find a solution or adapter that works?

FS: Nothing
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Oct 28, 2004
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Is Mini-Displayport and DisplayPort similar?

I recently bought a Lenovo T430 and it has a mini-DisplayPort.

I didn't go the adapter route but bought a mini-DisplayPort to HDMI cable and it works beautifully for audio and video.

I bought a Fosmon 6ft mini-DisplayPort to HDMI cable off Amazon.ca for $14:
https://www.amazon.ca/gp/aw/ya/ref=yo_i ... 42-9998630

FS: Nothing at the moment
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ji2o0k wrote: Is Mini-Displayport and DisplayPort similar?
They're the same, mini is just physically smaller.
ji2o0k wrote: I didn't go the adapter route but bought a mini-DisplayPort to HDMI cable and it works beautifully for audio and video.
That is an adapter, lol. I can't see your link but willing to bet it is a passive cable meaning you're getting native HDMI output. Again this is mainly possible on PC equipment because pretty much all DP ports (mini or otherwise) are D++ ports where passive adapters are able to set the DP to HDMI (or DVI) mode. On CE gear where DPs exist (and on inputs on monitors) DPs are typically not D++ ports, meaning passive adapters do not work; however since these instances are relatively rare in the consumer market, most cables with DP on one side and HDMI or DVI on the other side are passive cables.
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Mar 23, 2004
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This is an old thread, bumped, but I just noticed the Optiplex 780 is a C2D machine, likely with a 4-series chipset. I wasn't aware of this previously and assumed it was newer. This would be getting output for the on-board video connections from Intel GMA Graphics--likely something like GMA X4500. Pretty sure none of those older chipset-based video outputs supported audio at all. You'd need something Core iX (even first gen) to have any audio out of the video outputs. I believe that even using HDMI on the old 3 and 4 series chipsets (on the few boards that had it) would result in no audio unless it was internally connected to S/DIF output of a soundcard (either an actual soundcard or an on-board chip). This is much the same way that earlier Nvidia cards supported audio through HDMI, by merely connecting to the S/PDIF source elsewhere and amalgamating it with the TMDS stream.

Even if you could get audio, it'd be limited to 2ch PCM (and you could not get even compressed DD/DTS as DP doesn't support any Dolby or DTS formats at all). It's more than likely there isn't any audio connection at all for the DP on this machine. Being as old as it is though, I'd imagine OP has moved on from that system by now anyway.
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Feb 24, 2003
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I have an old dell 11z-1110 netbook with ddr2 and it supports multichannel pcm audio over hdmi after I installed the correct Intel display audio driver.

According to windows 10, 24 bit audio at 44.1, 48, 88.1, 96, 176.4, and 192 is supported over hdmi.

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