Hi everybody, I've finally got around to working on timestamping support for the uvcvideo driver. After a couple of years of development, it was about time.
The following patch set is divided in two parts. The first 3 patches implement debugfs support to export video stream statistics (thanks to Alexey Fisher for providing the initial implementation). As I don't know whether the Windows UVC driver makes use of device timestamps, I'm not sure how much the feature has been tested in devices. Having a way to retrieve statistics is thus vital to handle the stream of bug reports that might follow :-) The last patch implements device timestamps support. In a nutshell, devices report a timestamp based on their own clock. Converting from the device clock to the host clock requires going through an intermediate USB clock, shared between the device and the host. The code computes the linear relations from the device clock to the USB clock and from the USB clock to the host clock, and then converts the device timestamp to a host timestamp. Standard deviation in timestamps has been reduced by a factor of 10 with these patches. Precision could maybe be enhanced further by using the least min squares method to compute the linear regression. If anyone feels playful, please go ahead and submit an additional patch :-) Alexey Fisher (2): uvcvideo: Add debugfs support uvcvideo: Extract video stream statistics Laurent Pinchart (2): uvcvideo: Extract timestamp-related statistics uvcvideo: Add UVC timestamps support drivers/media/video/uvc/Makefile | 2 +- drivers/media/video/uvc/uvc_debugfs.c | 136 ++++++++ drivers/media/video/uvc/uvc_driver.c | 21 +- drivers/media/video/uvc/uvc_queue.c | 12 + drivers/media/video/uvc/uvc_video.c | 557 ++++++++++++++++++++++++++++++++- drivers/media/video/uvc/uvcvideo.h | 87 +++++ 6 files changed, 807 insertions(+), 8 deletions(-) create mode 100644 drivers/media/video/uvc/uvc_debugfs.c -- Regards, Laurent Pinchart -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
