Mailing List Archive: MythTV: Users

PCM type noise when HDMI cable is connected

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4romany at gmail

Feb 6, 2010, 8:01 PM

Post #1 of 4 (426 views)
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PCM type noise when HDMI cable is connected

Friend of mine build a mythbuntu system - got everything working in this
"lab" - using a 23in LCD with external speakers (connected to the computer
sound card). All well and good...disconnects the computer - takes and hooks
it to a HDTV - essentially the same way HDMI to DVI for video and analog out
of the sound card to the audio L/R of the TV - and all he gets is what to my
ears sounds like digital poping noise. I sold him this TV and on my myth
box - using the same type of connections - it worked fine. From what I
read DVI interface does not carry sound so I would not think there is a
setup issue on the computer causing the noise. From what he tells me the
video plays fine from myth - but only the poping sounds are heard.Possible
bad cable I suppose. Anyone have any insights on this? I hope to swing
by and look at it tomorrow.....

rafmoslin at gmail

Feb 7, 2010, 3:08 AM

Post #2 of 4 (404 views)
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Re: PCM type noise when HDMI cable is connected [In reply to]

On 7 February 2010 04:01, RALPH KEMP <4romany [at] gmail> wrote:
> Friend of mine build a mythbuntu system - got everything working in this
> "lab" - using a 23in LCD with external speakers (connected to the computer
> sound card). All well and good...disconnects the computer - takes and hooks
> it to a HDTV - essentially the same way HDMI to DVI for video and analog out
> of the sound card to the audio L/R of the TV - and all he gets is what to my
> ears sounds like digital poping noise. I sold him this TV and on my myth
> box - using the same type of connections - it worked fine.    From what I
> read DVI interface does not carry sound so I would not think there is a
> setup issue on the computer causing the noise.   From what he tells me the
> video plays fine from myth - but only the poping sounds are heard.Possible
> bad cable I suppose.   Anyone have any insights on this?   I hope to swing
> by and look at it tomorrow.....
>

Only thing I can do is agree with you that DVI-D does not do sound so
that the HDMI cable is unlikely to be the source of the problem. In
saying that should the TV audio source be set to get sound from the
HDMI input rather than its RCA's then there is perhaps the chance of
crosstalk causing the odd spurious 'pop' sound. Either way it seems to
me that the audio source is incorrectly set either on the PC output or
TV input.

Not a particularly useful response I grant you but hey, its a slow
Sunday morning!
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richardwoelk at yahoo

Feb 7, 2010, 9:46 AM

Post #3 of 4 (391 views)
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Re: PCM type noise when HDMI cable is connected [In reply to]

Rafael Moslin wrote:
> On 7 February 2010 04:01, RALPH KEMP <4romany [at] gmail> wrote:
>
>> Friend of mine build a mythbuntu system - got everything working in this
>> "lab" - using a 23in LCD with external speakers (connected to the computer
>> sound card). All well and good...disconnects the computer - takes and hooks
>> it to a HDTV - essentially the same way HDMI to DVI for video and analog out
>> of the sound card to the audio L/R of the TV - and all he gets is what to my
>> ears sounds like digital poping noise. I sold him this TV and on my myth
>> box - using the same type of connections - it worked fine. From what I
>> read DVI interface does not carry sound so I would not think there is a
>> setup issue on the computer causing the noise. From what he tells me the
>> video plays fine from myth - but only the poping sounds are heard.Possible
>> bad cable I suppose. Anyone have any insights on this? I hope to swing
>> by and look at it tomorrow.....
>>
>>
>
> Only thing I can do is agree with you that DVI-D does not do sound so
> that the HDMI cable is unlikely to be the source of the problem. In
> saying that should the TV audio source be set to get sound from the
> HDMI input rather than its RCA's then there is perhaps the chance of
> crosstalk causing the odd spurious 'pop' sound. Either way it seems to
> me that the audio source is incorrectly set either on the PC output or
> TV input.
>
> Not a particularly useful response I grant you but hey, its a slow
> Sunday morning!
> _______________________

Some TVs, like my Samsung, don't have a manual switch between HDMI and
analog audio. If the video card is capable of HDMI audio, and it
recognizes the TV can receive HDMI audio, it will be enabled.
The only way to fix this is to save and edit his tv's EDID information
and remove the HDMI audio portion. Then tell the X server to use that
EDID instead of reading from the tv. There have been a few threads on
this situation.

Ahh, its even on the wiki
http://www.mythtv.org/wiki/Configuring_Analog_Sound_DVI_to_HDMI

- Richard

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4romany at gmail

Feb 8, 2010, 5:00 PM

Post #4 of 4 (349 views)
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Re: PCM type noise when HDMI cable is connected [In reply to]

Just to bring closure to this thread (yeah - makes me quesesy just saying
it): my friend video card has a DVI interface - but is apprently capable
of carrying sounnd - there is a way to strap (SPDIF?) from the MB to 2 pins
on the card. I connected the PC to my TV - got the same no sound -
disconnected the DVI cable from PC - analog sound is heard. Replaced this
card with a different Nvidia - everything worked...

Thanks for the replies - there should be some way of disabling this on the
card - but I'll let my friend pursure that.

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