The MM_DRVM_ERROR video capture message is sent to a client when a user-mode video capture driver detects an error.
Parameters
dwMsg
MM_DRVM_ERROR
dwParam1
Number of frames dropped.
dwParam2
Not used.
Comments
A user-mode video capture driver sends an MM_DRVM_ERROR message to its client, by means of a callback, when the driver detects an error. The driver sends the message to the client by calling DriverCallback, passing the specified parameters.
A driver can send this message for any reason, but the message is typically used to report dropped frames. The driver drops frames if the client has not provided enough buffers to receive them. Drivers use the dwParam1 argument to indicate the number of dropped frames.
The driver sends the MM_DRVM_ERROR message only if the client has previously specified a notification target with a DVM_STREAM_INIT message.
Drivers using VCUser.lib do not have to call DriverCallback to send callback messages. Code within VCUser.lib handles delivery of callback messages for the driver.
For more information about notifying clients, see Notifying Clients from Video Capture Drivers.