Media Foundation Source Reader: ReadSample is not cancelled by Flush
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Schaefer, Joerg
1
Reputation point
A synchronous Source Reader 'Read Sample' function call is made to an UVC camera media source and no image is returned by the camera. The function call blocks and is not cancelled by 'Flush'.
How can a pending synchronous ReadSample() call be cancelled?
Windows development | Windows API - Win32
{count} votes
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Rita Han - MSFT 2,171 Reputation points2021-02-08T02:24:52.583+00:00 Hello @Schaefer, Joerg , do you mean calling IMFSourceReader::Flush() can't get IMFSourceReader::ReadSample() return? What's return value of the
IMFSourceReader::Flush()? -
Schaefer, Joerg 1 Reputation point
2021-02-08T07:33:08.393+00:00 Neither Flush() nor ReadSample() do return at all!
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Rita Han - MSFT 2,171 Reputation points
2021-02-09T01:21:19.043+00:00 Thanks for confirmation. At what condition this issue occurs? Is it related to camera's status?
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Schaefer, Joerg 1 Reputation point
2021-02-09T08:15:09.103+00:00 The video source is an UVC camera device (USB 3.0, UVC 1.1, bulk streaming) operating in triggered mode.
The behaviour is seen when no trigger is activated to the camera, i.e. when it is not delivering a video sample to the PC anymore.
IThe behaviour does not change if video samples were delivered previously.On the host side, an application is waiting for samples through the (synchronous) source reader using a 'ReadSample()'.
Stopping this request is required to proceed with the application and was tried by using 'Flush()' on the same source reader instance.
Several tests with putting the Read or Flush in different threads or a 'SetWaitableTimer' callback didn't succeed.
However, all these tests do show effect when the 'asynchronous' source reader is used, therefore we do not think its an application/threading problem. -
Rita Han - MSFT 2,171 Reputation points
2021-02-09T09:30:50.127+00:00 Thanks for detailed information. I'll consult the related engineer for helping on this issue.
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Schaefer, Joerg 1 Reputation point
2021-03-04T09:15:37.45+00:00 Is there any update on this issue, yet?
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