WaveOut API on Win7 Question

[iank]

We are using the waveOut API to play audio in our application and are getting
an error from waveOutOpen.
We are cooperating with another application which also plays Audio and it
should have released the audio channel by the time we try to open it. As a
result, this error occurs intermittently. I had assumed that it was possible
for multiple applications to use the waveOut API to play audio and the
results would be mixed together. However, this does not seem to be the case.
Is exclusive use the normal behavior or is there something about the
configuration or driver that is causing this?
How can we fix or work around this behavior?

[John Doe]

Post by iank
We are using the waveOut API to play audio in our application and are getting
an error from waveOutOpen.
We are cooperating with another application which also plays Audio and it
should have released the audio channel by the time we try to open it. As a
result, this error occurs intermittently. I had assumed that it was possible
for multiple applications to use the waveOut API to play audio and the
results would be mixed together. However, this does not seem to be the case.
Is exclusive use the normal behavior or is there something about the
configuration or driver that is causing this?
How can we fix or work around this behavior?

Multiple application can use the waveOutOpen API only if driver permits
that. In that case driver will do the mixing.
Otherwise you will not be able to open device more than once.
You can try with different driver for the same hardware (if available) or
try with different sound card.

[Bob Masta]

On Wed, 30 Dec 2009 01:15:02 +0100, "John Doe"

Post by John Doe

Post by iank
We are using the waveOut API to play audio in our application and are getting
an error from waveOutOpen.
We are cooperating with another application which also plays Audio and it
should have released the audio channel by the time we try to open it. As a
result, this error occurs intermittently. I had assumed that it was possible
for multiple applications to use the waveOut API to play audio and the
results would be mixed together. However, this does not seem to be the case.
Is exclusive use the normal behavior or is there something about the
configuration or driver that is causing this?
How can we fix or work around this behavior?

Multiple application can use the waveOutOpen API only if driver permits
that. In that case driver will do the mixing.
Otherwise you will not be able to open device more than once.
You can try with different driver for the same hardware (if available) or
try with different sound card.

I think the above restrictions are for older
Windows versions. Most systems have only a single
sound card, shared by all the apps. As I
understand it, under Vista and Win7 each app acts
independently, as though it had the card to
itself, via emulation by Windows. Windows mixes
all the waveOut streams (including sample rate
conversion, etc) via the Kernel Mixer and feeds
them to the single sound card output stream. The
driver need not be aware of any of that, since it
sees only the single combined stream.

Best regards,


Bob Masta

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[John Doe]

Post by Bob Masta
I think the above restrictions are for older
Windows versions. Most systems have only a single
sound card, shared by all the apps. As I
understand it, under Vista and Win7 each app acts
independently, as though it had the card to
itself, via emulation by Windows. Windows mixes
all the waveOut streams (including sample rate
conversion, etc) via the Kernel Mixer and feeds
them to the single sound card output stream. The
driver need not be aware of any of that, since it
sees only the single combined stream.

I have had a professional sound card on Windows XP on which I was not able to
open waveOut more than once. Even the error code for the second open attempt
said something like that. At the same time (on the same system) I was able to
open waveOut more than once on the sound card integrated on the motherboard. I
might be wrong, but it seems like a driver "issue".

P.S.
Happy new year!!! :-)