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Author Topic: EPKK help  (Read 4422 times)
mienki
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« on: May 06, 2014, 02:39:13 PM »

Hi,

Can you please listen to EPKK and tell why it is not perfect Smiley
When I use headphones plugged directly to the scanner it is perfect;
Is it caused by codec or what...?
Any ideas?

raspberry pi + usb sound card+ stereo cable

http://allegro.pl/profesjonalna-karta-dzwiekowa-muzyczna-usb-7-1-3d-i4123304044.html

Best regards,
mm
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mienki
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« Reply #1 on: May 08, 2014, 08:38:35 AM »

it is now alive so if you could please listen to it and give any solution i would be glad Smiley
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mienki
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« Reply #2 on: May 19, 2014, 01:12:38 PM »

still no ideas?
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InterpreDemon
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« Reply #3 on: May 19, 2014, 02:36:28 PM »

Are you using the line input or the mic input on that USB box? Have you tried both?

I've heard this effect before, I think it was when I was running a stereo feed with the bitrate too low, but you are running mono. Could be the codec, but the first thing I would do if running the line input would be to use a Y cable or mono female to stereo male phono adapter plug to "bridge" the audio across both channels and make sure I was feeding identical input audio to both channels. If you are using the left and right channels for two radios and trying to "mix" them through the mono conversion this effect can happen... you would better off mixing them externally. Some sound cards will always A/D the stereo signal and where the difference between the signals (say, audio on only the left channel) is extreme you get this problem if the sample rate and/or bitrate is too low. Some sound cards simply can't encode 90-100db channel isolation very well at all, assuming that most stereo signals are music with not a lot of difference between the channels so they can get away with higher levels of compression. It could be hardware limitations, firmware or software, hard to say at this point, but bridge that line input first and we'll take it from there.
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Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
mienki
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« Reply #4 on: May 20, 2014, 11:55:02 AM »

thanks for reply.

I use mic input. When I changed the input for line I could here nothing.
I use 1 scanner (which scans 3 different freq.) which is connected to the usb card via stereo cable.
(3.5mm output from the scanner to 3.5mm mic input of sound card via stereo cable )
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InterpreDemon
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« Reply #5 on: May 20, 2014, 01:28:20 PM »

It is likely that your stereo cable is only making contact on one channel (center pin) in the scanner jack, thus only feeding one channel on the sound card. You need to get a 3.5mm female stereo to 3.5mm male mono adapter, plug that into your scanner, then plug your stereo cable into that. Here's an example of the adapter: http://www.amazon.com/Stereo-Female-Mono-Male-Adaptor/dp/B000I97G0A
« Last Edit: May 20, 2014, 01:30:49 PM by InterpreDemon » Logged

Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
mienki
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« Reply #6 on: May 20, 2014, 03:14:16 PM »

i will let you know after change.

thanks
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mienki
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« Reply #7 on: May 20, 2014, 03:44:55 PM »

mono cable now and still the same :/
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InterpreDemon
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« Reply #8 on: May 20, 2014, 04:27:25 PM »

Just plugging in a mono cable would not solve the problem, it still would only feed one channel in the mic input jack, which is stereo, and the other channel would be grounded. You need to be feeding both mic input channels with the identical signal, meaning you either need to use a stereo cable with stereo/mono adapter at the scanner, or a mono cable with mono/stereo adapter at the mic input. If you look at a stereo plug, there is a tip (left audio), followed by a ring (right audio) and then the barrel (common signal ground), whereas the mono plug only has the tip and barrel. When you plug a stereo plug into a mono jack you only get contact with the tip, and when you plug a mono plug into a stereo jack you get the same thing (only the left channel) except the right channel is shorted to the barrel.

What we are trying to do here is make sure we are feeding audio to both input channels so that we can rule out a hardware, firmware or software issue when encoding stereo with only left channel signal and then converting to mono downstream in software. Some sound cards have the ability to be configured for mono by specifying which channel to use, left or right, or "both", in order to obtain the mono signal. If you do not have those options, you need to bridge the inputs so that it does not make any difference, and if you do have those options you should only specify left or right (whichever has the signal, with a mono cable it would be the left) and NOT "both"... which would mix the channels (one live and the other dead) in software and possibly lead to the artifact we are hearing.
« Last Edit: May 20, 2014, 04:29:03 PM by InterpreDemon » Logged

Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
mienki
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« Reply #9 on: May 22, 2014, 02:56:53 AM »

ok. now I get it.
i will change it today.
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mienki
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« Reply #10 on: May 22, 2014, 04:01:05 AM »

cable changed. nothing has changed.
i think it is due to codec/codec settings.

anybody could help me to set the codec?.
I dont konw raspbian and They set this up remotely.

If anybody could write me some commands to check settings/set up codec parameters i would be grateful.

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InterpreDemon
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« Reply #11 on: May 22, 2014, 11:29:13 AM »

Personally, I'd try a different sound card like a Griffin, which many are using with good results, before I drilled that deep into the software.
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Feed Purveyor:
KJFK ARINC
KHPN ATIS
(KJFK) NY DEP Liberty East
HF CAR-A  3455/5550/6577/8846/11396
HF ARINC LDOC  6640/8933
HF NY VOLMET  6604

Complaints should be addressed to: City Hall
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