[WT-support] Contest recorder: recording from USB device

[Bob Wilson, N6TV]

Good report Frank.

73,
Bob, N6TV

On Tue, Sep 25, 2012 at 1:44 PM, dl2alf <dl2alf at arcor.de> wrote:

> Hi,
>
> Our contest crew is running several portable configurations of Win-Test
> together with USB sound cards for recording RX audio (V4.7.0 + Microkeyer +
> USB sound cards).
> Configuration of the contest recorder within Win-Test is proved, most of
> the
> 24 contest hours everything is running fine.
> For some reason the connection to the USB sound card is lost for a moment.
> This might be caused by EMI, driver problems or if someone diconnects the
> USB cable by mistake.
> If that happens you will get the following behavior:
>
> - recording stops without error message (neither from Win-Test nor from
> operating system)
> - the MP3 output file is not written anymore
> - beside recording, Win-Test is fully operational that time, so this might
> be unnoticed for a long time (you will loose hours of RX recordings that
> way!)
> - the situation won't change if the USB sound card is back again
> - if you try to stop capturing, Win-Test hangs and must be closed via Task
> Manager
>
> To reproduce this just do the following:
>
> - connect an USB sound card to your PC (can be a Microkeyer internal USB
> sound card as well)
> - start Win-Test
> - open contest recorder window and go to the MP3 configuration menu
> - set the recording sound device to that USB sound card input, don't care
> about the other options
> - start recording
> - disconnect the USB sound card while recording
> - (optional: connect the USB sound card again)
> - try to stop recording
>
> --> Win-Test hangs as a result
>
> I did some investigations to find out what's going on there. For that, I
> was
> writing some software for audio capturing based on C# and .NET and using
> Microsoft DirectSound and Lame as an audio compressor. ( it's just a "proof
> of concept", the source code is available on request). I guess that this is
> basically the same idea as used in Win-Test.
> Here is what I could find out so far:
>
> - the above mentioned behavior is NOT depending on the operating system
> (tested on WinXP and Win7)
> - the above mentioned bevavior is NOT depending on Win-Test version (tested
> up to V4.7.0)
> - it seems, that the Microsoft DirectSound subsystem simply stops working,
> when the USB sound card is disconnected -->  you won't get any software
> exception as a notification
> - any thread in the software layers above consuming kind of "Audio data
> available" event just hangs in an infinite loop
> - while trying to stop audio capture, a software exception is generated
> called "NoDriverException" (which is too late and is probably not handled
> by
> Win-Test)
>
> To aivod this and to get a more robust software, I'd suggest the following
> improvements in Win-Test:
>
> - periodically check the increasing length of the MP3 output file while
> recording
> - if the length is not increasing anymore, something is wrong with the
> audio
> source (it might be lost or disconnected), so do:
> - stop recording asynchronously and handle the upcoming "NoDriverException"
> properly
> - periodically check for the previosly selected audio device is present
> again, if yes:
> - resume recording
>
>
> I'd like to know if somebody else has experienced the same and likes to get
> into a discussion on that topic. Any answer is highly appreciated.
>
> Best regards,
>
> Frank, DL2ALF at DL0GTH
>
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