View Full Version : Operational Cockpit Voice Recorder (CVR)

12-21-2009, 06:17 AM
Hey Everyone,

I've been thinking about this idea of having an operational CVR in the simulator. I first searched the internet and could not find anything specific to just recording the pilots' voices. You can get a lot of programs that work like "Black Boxes" from the flight data point of view, but not with voice.

That made this more interesting. It would be nice to have the flight data/flight simulator replay with the pilots voice; this assumes you do voice interaction with a virtual airline or multiplayer/ATC.

Anyway, what I looked at was a way to keep it simple and use a program that is found already on your computer. Windows Sound Recorder is one of the oldest recording programs on Windows. It's right there in the Start>All Programs>Accessories>Entertainment. This is how I see it working.

This is done a different computer from your FS9/FSX computer:

1. A small desktop microphone connected to a computer's sound card mic input and placed in the CVR spot, in the overhead (behind).

2. If you want to hear what ATC is saying included, then you would have to use a cable(s) coming from the FSX computer that would plug into the, lets call it, CVR computer's sound card (more on the wiring later).

3. Using FSUIPC, you would setup a trigger, through your I/O card, to trigger a keyboard shortcut and in this case the space bar, from the Overhead CVR buttons, either the black (test) or red (erase). I like red-for recording...

4. Using Sound Recorder, it has no keyboard shortcuts. However, when you first open the program you'll see that the red record box is highlighted in a way with dashed lines. If you press the space bar, recording starts, if you push space bar again it stops, press it again and it records again. So, this makes it a one button recorder.

5. You could use a different audio/recording progam that has keyboard shortcuts and assign the black button for stop and the red for record. It might not be a free program though. But, you could change things like the record quality/compression rate; the lower quality compression means longer record times without using up all the hard drive space on the CVR computer. Plus, it'll sound cheap just like the real CVR voice recordings do.

Finally, I'm sure there are more things one could do with this idea and if someone comes up with something like macros to control the buttons of the recorder program or whatever post about it. Also, I am just thinking B737 here, but if someone can do this in another aircraft, please post about that too...

12-21-2009, 06:52 AM
Interesting I was thinking about this during the weekend. I was thinking more of the modules that let you record some voice and then play it back, a simple electronic circuit. the problem with these is you are limited to about 20 secopnds of voice, .... now if someone with som electronic know-how could merge something like that with a USB stick you'd have an inexpensive solution for a low price.

12-21-2009, 08:14 AM
Same things I've been thinking as well. I've seen some cheap DVR type units and other cheap audio recording devices, and USB interfacing would work. Plus, you're right about the limited time recording.

Here is one I had in mind. Radio Shack sells a portable cassette recorder controller (yes, I said cassettes...like prehistoric now) that allows you to hook it up to your telephone. I have this already.

Link here:


It has a switch for recording and another switch for playback. The telephone receiver on your phone is what activates the switch. That could be wirred to the CVR push-button and thereby, leaving out a computer, FSUIPC, other sound cards and all.

As for the cassette recorder I have this one:


Now, I've used this on the telephone line before and the cool aspects are this. If you get long playing tapes like Maxell 120's, they'll give you two hours of recording time. The recorder has auto flip. That means it'll record to both sides without physically removing the cassette tape. Other aspects include; you can use long microphone cables and leave the recorder outside the sim, you can save the tapes with flight data (not on the same tape mind you), and you would not spend a lot of money on this.

I do know that someone might suggest to just use a video DVD recorder with connections to the output audio and video of the FS9/FSX computer, and that is a good idea too. That would show the flight for later playback and could be used to give to people who are visiting your sim. Like what Flight Experience or a real airlines simulator service would do.

However, that does not simulate what the CVR really does. The CVR is just hissing old audio tape playing back. Besides, it's a cheap approach. Still, it would be nice to do the CVR and use a DVD recorder together to have more to watch and listen to later...

I think that there are many ways to do this, an old unused computer with a DVD-R or RW, a cheap video capture card with RCA input/output connectors would do the same. Funny as this sounds, I have all these items lying in a drawer somewhere and as I type this, I think I might try this myself...talk about stimulating my mind while I type.

Anymore ideas from everyone, just chime in...

12-22-2009, 05:53 PM
Hi guys,

Excellent idea. I use to fly online and it would be nice to be able to lesson to the dialog with the ATC at the end of a flight (some times, we desagree ...)

Of course it is possible to use external recorders, but I would rather use my PC as a voice recorder : less electric cords (I have too much of them) and no loss of quality. With a little imagination I believe it is possible to start it from the overhead panel (hardware or software) like in a 737.

Characteristics to look for :
- compact format of recording such as MP3 or low fi (8 bits, 11 Khz)
- stop recording during silences.

There are plenty of these software on the net. If I have a moment I will give a try and keep you informed.

Merry Xmas


12-22-2009, 06:42 PM
Hi Cakus,

Of course it is possible to use external recorders, but I would rather use my PC as a voice recorder : less electric cords (I have too much of them) and no loss of quality. With a little imagination I believe it is possible to start it from the overhead panel (hardware or software) like in a 737.

I agree on less wires is more :) but if we were to come up with let's say a small circuit board with a power connector and an USB port then you could just power it off of your overhead power supply. You have 5v or 12v (or both) on your over head anyway to power your LED's and gauges. If we use USB then you don't have to worry about space issues, a lot bit stream could be stored for hours and hours on a 1GB stick.

I would not worry about something that only records when there is sufficient sound (voie activated) because you are going through the checks either with a copilot or reading them out to yourself, OR you have your cockpit sounds OR you have your FS sounds or any mixture of the above mentioned.

Just my 5 eurocents :)

12-23-2009, 12:19 AM
Just my 5 eurocents :)

To us Americans that's worth alot LOL

This is a very cool idea

01-03-2010, 10:10 PM
this beautiful idea acually ..

i think with the use of DPDT(duoble pole duable throw ) microswitch for the mic > first pole to trigger the recording and the other transmit (capslock in MP)
SO we have recording for outgoing messages ....

now we need to find a way to record the incoming messages :roll:

thanx for the topic:p

01-27-2010, 11:52 AM
Hi guys,

Great topic, I have been using an old mini disc player/recorder I had at home. I have a 12 channel audio mixer I use for patching various sounds to various speaker systems around the sim. I had a line out off the CVR mic going via an AUX send to the mini/disc. Worked a charm. But as others have suggested a PC based system would be far better and easier to maintain. Am I right in saying real CVRs only record thirty mins of audio before the loop erases and rolls again?


01-27-2010, 02:08 PM
Hello Everyone,

I have been working a little on this topic since my first post.

First, I wrote a little recorder program (C++). It is quite LO-FI (9 Khz, 8 bits, mono) in order to save disk space but the quality is sufficient for our purpose. The particularity of this recorder is to be interfaced with FS via FSUIPC. The recording in the file begins automatically when the flight is active in FS. It pauses / starts with FS. An FSUIPC offset can be defined in order to start / stop the recording. This way, it is possible to command the recording via a PTT button or via a switch of the overhead panel. Sound capture is done using a little electret mic.

My first proposal was to record directly the sound that comes from the computer without remiking (ATC voices for instance). As a musico, I hate the idea of remiking. But I must say that it is not that simple. Windows doesn't allow (in my knowledge) to consider the sound output of a program as the input of another program. I found only one (affordable) software solution : it is called Virtual Audio Cable. It is a sort of virtual sound card where an output channel may be considered as an imput channel for another program. It cost around 20 USD and a free demo is downloadable. I tried it but did not obtain perfect results with TeamSpeak on my config. So, I give up for the moment. If you want to try : http://software.muzychenko.net/eng/vac.html

Another solution to avoid remiking would be to use an SPDIF connection beween two computers : of course, there is a cable but you are totaly digital so no need to adjust the recording level, no risk of overload, no loss of quality. But you need audio cards with SPDIF input and output.


01-27-2010, 09:36 PM
this is quit impressive patrick :D
i didnt knew anything about SPDIF before this ,, and im gonna try and find out some stuff about using it :)
AND, about the c++ thing .... awsome
making such module would be a first in the market
i was wondering .. does project magenta instructor station do the job ,i mean does it record flight data and voice ??


Glenn Weston
01-29-2010, 12:57 PM
Hi Guys, I bought this up on another forum "viperpit.org".

I thought a CVR would be fantastic particularly if you were doing combat type flying, but there didn't seem to be alot of interest in what I mentioned back there.

It would certainly be good for going back over ATC instructions to make sure you got things correct after your flight.
I have seen people get into large forum fights in the online ATC arena just because of something that might have been said or missed over the radio whilst flying online, so I think it would be a benefit to have a CVR particularly with online flying.

There is a free program called Xcorder, originally written for Ham radio applications for recording from an audio jack of a radio, It has voice activation (VOX) also to save space during recording sessions, The Sensititvity of the activation is adjustable so if you want to just keep recording during quiet times that can also be done.

Whilst I have not implimented the program in my sim, I have run a few little tests just on a PC & it seems like it will do the trick.
I have actually tested & had woking a real aircraft intercom system that I have interfaced to the PC sound card ( Very easy to do & very realistic). Intercoms are pretty cheap on Ebay. Some of them even have options for Music input from a music radio or ipod so you can listen to some music while you are flying along.

My idea is to run one of the intercom headset outputs to the Xcorder pc & then all will be recorded (Pilot to Co-Pilot) (Pilot to ATC) (ATC to Pilot)etc. so you have all bases covered. I actually have a copy of the software & can post it somewhere if required so you guys can have a play with it, I originally downloaded it from some corner of the Web but I don't have a link.

A google search should track it down otherwise just let me know, it is a free app so I think we could even host it here somewhere.
A Screen shot of the Application is attached.

Regards Glenn.

01-29-2010, 04:11 PM
The official page and download link is: http://www.gromkov.com/faq/capture/xcorder.html

Glenn Weston
03-12-2010, 09:54 AM
Just thought I would add a little further info on this xcorder program, apparently it also had a name change & is now called vox2file.

I recently also was a passanger with a mate of mine on an IFR flight from Bankstown to Canberra (Australia) in a Piper cheiftan.

I decided to plug in a Y adaptor to the headset socket in the plane, didn't get all technical & worry about impedence matching etc. just a straight split & fed the audio from the intercom to the mic input on my EEEPC 901 & used xcorder to record all the cockpit audio, the results were fantastic.

I recorded the whole flights audio, cockpit & ATC.
I decided to record continuousley....the file size was about 30Mbytes at lowest (default) sample rate & 350Mbytes at CD quality, both samples are very good to listen to on playback. This was about 50 odd minutes of recording I adjusted the sample rate on the return trip.

Cheers Glenn.