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Audio Static On Four Channels


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#1 MrCurlyWhirly

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Posted 31 March 2012 - 03:11 PM

Hi Everybody,

We live on the coast side of Montville, about 5km from the Dulong transmitter, and today for the first time after being here two years+, i decided to watch the AFL on 7mate. I can definitely WATCH it, the picture is perfect, but the audio is just continual low frequency static, with no discernable commentary - its flooded with noise. My partner sees this as a feature :kiss:

I checked the rest of the digital channels and found a similar problems on three others:
24 - 767MHZ
50 - 662 MHZ
63 - 788 MHZ
80 - 809 MHZ

The wierd thing is that other channels transmitting on similar frequencies are clear as a bell, ie all the ABC channels, the other channel 7s etc.

I suspected it may be RF being generated by our solar inverter, which is about three meters away from the PVR, on the outside wall. I switched that off and rechecked - it made no difference.

Any ideas? or has anybody had similar problems?

99% of my viewing is in the evenings, so i cannot say how long this interference has been a problem.

#2 digitalj

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Posted 31 March 2012 - 03:21 PM

it's something to do with the Dolby Digital Decoder. Try turning it off at the power point for 10 seconds then turning it back on.

#3 MrCurlyWhirly

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Posted 31 March 2012 - 06:28 PM

Thanks for the suggestion. The unit is essentially a PC - mATX MB with a Hauppage dual video card. I now know it has nothing to do with the solar array messing with the audio component of the video signal, it still has the same symptoms - and its now dark!

I did give the unit a soft restart earlier - which made no difference. Last night i watched the Hawks crush Collingwood on 63 with no audio problems evident. After the game finished i loaded up an MS service pack on the machine and a few windows updates. Normally i would expect decoding issues to be a problem across all channels if it had anything to do with the SP, anyhow i will try the PWR Reset and reload the audio drivers if its still a problem.
.

#4 MrCurlyWhirly

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Posted 31 March 2012 - 08:40 PM

Well its still a mystery, power reset made no difference, neither did rolling forward from 6.01.5612 Relatek ATI HD Drivers to 6.0.1.6519. The four digital channels are still only generating the same static noise. Its not Dolby decoder related, as some of the other channels are recieving Dolby stereo without any problems. I do agree though that it could well be codec related, just do not see where to go with this next.

Any suggestions?

Edited by MrCurlyWhirly, 31 March 2012 - 08:49 PM.


#5 digitalj

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Posted 31 March 2012 - 11:47 PM

24, 50, 63 and 80 use Dolby Digital, the remaining services use MPEG Audio.

It was never going to be anything to do with solar arrays or other interference as the picture is working for you and the other services on the same multiplexes work for you as well.

#6 MrCurlyWhirly

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Posted 01 April 2012 - 02:41 PM

According to the transmission info there was dolby digital being picked up on some of the channels with good audio, are you saying this audio is stripped from the MPEG stream, while the other dolby digital on those four static channels is transmitted differently requiring a different level of decoding?

#7 MrCurlyWhirly

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Posted 01 April 2012 - 03:16 PM

OK, forget those questions, you are dead right! After checking each channel again i can see the problem clearly now, when i go to one of the four channels with dolby digital i am getting continuous static, then the NEXT channel i select is logging in the info line as 'dolby digital', if i toggle to the same channel from a good audio channel this does not appear, so i suspect you hit the nail on the head first time.
I am not entirely sure how to resolve this, all the audio drivers have been updated, will start by rolling back from SP2 in case that has touched something it should not have that is somehow effecting the decoding.
Any further suggestions on how to resolve this would be appreciated. When i run the dolby test in the Realtek sound utility i am getting the same static sound, are there any other diagnostic aids available for sound chip level troubleshooting?

#8 MrCurlyWhirly

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Posted 01 April 2012 - 03:26 PM

I probably should have checked this yesterday to save myself some grief ... streaming to another PC on my n/w (with its own copy of media center) resulted in perfect audio playback, so the capture is fine, just the decoder on the PVR is the problem.

#9 digitalj

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Posted 01 April 2012 - 04:30 PM

try installing the appropriate version of shark007: http://shark007.net/

#10 digitalj

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Posted 01 April 2012 - 04:36 PM

According to the transmission info there was dolby digital being picked up on some of the channels with good audio, are you saying this audio is stripped from the MPEG stream, while the other dolby digital on those four static channels is transmitted differently requiring a different level of decoding?


MPEG doesn't carry Dolby Digital, it can how ever be surround encoded which can then be decoded to multiple channels with Dolby Prologic II, DTS Neo:6, etc.

#11 MrCurlyWhirly

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Posted 01 April 2012 - 09:20 PM

Thanks for the help. I installed those codecs this evening and the audio is now fine on those 4 channels. I guess the only difference will be a slight increase in cpu load doing software decoding rather than using the realtek chip. I am interested to know how to troubleshoot the underlying fault, the SP2 rollback made no difference, and according to the Realtek utility (and Windows) the audio chip was working properly. It needs lower level debugging, but for now this is a very welcome solution!