ATC audio being recorded

Interesting ATC clips and situations from PilotEdge

Re: ATC audio being recorded

Postby Keith Smith » Sat Jan 07, 2012 6:44 am

Here are the daily files for January 6.

Jan 6 app/center (mp3)
Jan 6 del/gnd/twr (mp3)

These only cover about 1/3 of the day because the voice server was restarted during the early afternoon due to a resource exhaustion issue on that machine (it's on the same machine as the drones, and the machine needs a reboot every 6 weeks or so).
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Re: ATC audio being recorded

Postby Keith Smith » Sun Jan 08, 2012 6:49 am

Here are the daily files for January 7.

Jan 7 app/center (mp3)
Jan 7 del/gnd/twr (mp3)

I think the unanswered radio checks at the start were before the published operating hours
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Re: ATC audio being recorded

Postby Orest Skrypuch » Sun Jan 08, 2012 1:35 pm

Keith,

What software are you using to accomplish this? I have on/off looked for some simple windows software that could record the input/output of a USB mic, with voice activation to eliminate the dead spots.

* Orest
PP/ASEL/IR, Piper Dakota (PA28-236) C-FCPO
President & CEO, UVA, http://www.united-virtual.com
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Re: ATC audio being recorded

Postby Keith Smith » Sun Jan 08, 2012 2:32 pm

Orest,

It's non-trivial. I wrote a client that connects to the voice server (much like the controlling client and pilot clients). There is an option to record the received audio as a 32-bit floating point raw PCM stream. We take that data and write it to a pipe which feeds into the 'sox' utility (Linux) to convert it to a 16-bit int PCM format. Every hour, the utility kicks off a background task which takes that file and pipes in into sox to create a WAV stream, and passes THAT into the MP3 encoder. The file is then copied with 'scp' up to our web server.

The silences are not being manually removed, it's just a nice artifact of the architecture. We are only passed the data when someone is actually talking, so the resulting file only contains the actual transmissions.

This took a long time to build, largely because of the format conversions (I tried to keep it simple, but the various converters didn't work, so I ended up with the long, complex chain that you see above). Only the last conversion is lossy, though, so quality-wise, we're in great shape, as you can hear by what's in the files now.
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Re: ATC audio being recorded

Postby Keith Smith » Mon Jan 09, 2012 8:55 am

Here are the daily files for January 8.

Jan 8 app/center (mp3)
Jan 8 del/gnd/twr (mp3)

If anyone has any issues playing either of those, let me know. I failed to restart the 'daily recorders' (that part is a manual process each morning) on Sunday morning. I actually assembled the daily recordings by concatenating the hourly recordings (which are humming along in an automated fashion) with some server-side utilities.
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Re: ATC audio being recorded

Postby Steven Winslow » Mon Jan 09, 2012 11:14 am

Now honestly, Keith, tell me you had to use a thesaurus to come up with "concatenating." Thanks for the vocab lesson!
Steven Winslow
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People should get what they want when they want it once in a while. Keeps them optimisitic.
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Re: ATC audio being recorded

Postby Keith Smith » Mon Jan 09, 2012 12:06 pm

Must be a software developer thing :) That word comes up quite frequently, believe it or not!
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Re: ATC audio being recorded

Postby Andrew Miller » Mon Jan 09, 2012 8:49 pm

Keith Smith wrote:Must be a software developer thing :) That word comes up quite frequently, believe it or not!

A day doesn't go by in my job where I don't use that word.
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Re: ATC audio being recorded

Postby Keith Smith » Tue Jan 10, 2012 7:57 am

Here are the daily files for January 9.

Jan 9 app/center (mp3)
Jan 9 del/gnd/twr (mp3)

They're pretty short, traffic was light during the day with a brief spike in the evening.
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Re: ATC audio being recorded

Postby AviatorScott » Tue Jan 10, 2012 2:26 pm

Hey,
This is a great service, I joined to work on my clearance "correctness", the hardest part of flying IFR is getting that clearance correct, (and keeping the passengers from screaming on those approaches to minimums :) )! Thus listening to the shortened list of clearance requests is great. Question though, I see several posts about "new interface" and hourly recordings, do we have an idea on when that will become functional?

Thanks,
Scott
Scott Woodland, PE, M.ASCE
PPL - ASEL -- IFR
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