Merge pull request #12893 from aleksey-nikolaev:cap-update

V4L (V4L2): Refactoring. Added missed camera properties. Fixed getting `INF` for some properties. Singlethread as always (#12893)

* cap_v4l:
1 Added cap_properties verbalization.
2 Set Get of properties elementary refactoring.
3 Removed converting parameters to/from [0,1] range.
4 Added all known conversion from V4L2_CID_* to CV_CAP_PROP_*

* cap_v4l:
1. Removed all query for parameters range.
2. Refactored capture initialization.
3. Added selecting input channel by CV_CAP_PROP_MODE. Default value -1 the channels not changed.

* cap_v4l:
1. Refactoring of Convert To RGB

* cap_v4l:
1. Fixed use of video buffer index.
2. Removed extra memcopy for grab image.
3. Removed device closing from autosetup_capture_mode_v4l2

* cap_v4l:
1. The `goto` was eliminated
2. Fixed use of temporary buffer index for V4L2_PIX_FMT_SN9C10X
3. Fixed use of the bufferIndex
4. Removed trailing spaces and unused variables.

* cap_v4l:
1. Alias for capture->buffers[capture->bufferIndex]
2. Reduced size of data for memcpy: bytesused instead of length
3. Refactoring. Code duplication. More info for debug

* cap_v4l:
1. Added the ability to grab and retrieveFrame independently several times

* cap_v4l:
1. Not need to close/open device for new capture parameters applying.
2. Removed using of device name as a flag that the capture is closed. Added sufficient function.
3. Refactoring. Added requestBuffers and createBuffers

* cap_v4l:
1. Added tryIoctl with `select` like was in mainloop_v4l2.
2. Fixed buffer request for device without closing the device.
3. Some static function moved to CvCaptureCAM_V4L
4. Removed unused defines

* cap_v4l:
1. Thread-safe now

* cap_v4l:
1. Fixed thread-safe destructor
2. Fixed FPS setting

* Missed brake

* Removed thread-safety

* cap_v4l:
1. Reverted conversion parameters to/from [0,1] by default for backward compatibility.
2. Added setting for turn off compatibility mode: set CV_CAP_PROP_MODE to 65536
3. Most static functions moved to CvCaptureCAM_V4L
4. Refactoring of icvRetrieveFrameCAM_V4L and using of frame_allocated flag

* cap_v4l:
1. Added conversion to RGB from NV12, NV21
2. Refactoring. Removed wrappers for known format conversions.

* Added `CAP_PROP_CHANNEL` to the enum VideoCaptureProperties.
CAP_V4L migrated to use VideoCaptureProperties.

* 1. Update comments.
2. Environment variable `OPENCV_VIDEOIO_V4L_RANGE_NORMALIZED` for setting default backward compatibility mode.
3. Revert getting of `CAP_PROP_MODE` as fourcc code in backward compatibility mode.

* videoio: update cap_v4l - compatibilityMode => normalizePropRange

* videoio(test): V4L2 MJPEG test

`v4l2-ctl --list-formats` should have 'MJPG' entry

* videoio: fix buffer initialization

to avoid "munmap: Invalid argument" messages

modules/videoio/include/opencv2/videoio.hpp

@@ -169,7 +169,8 @@ enum VideoCaptureProperties {
        CAP_PROP_AUTOFOCUS     =39,
        CAP_PROP_SAR_NUM       =40, //!< Sample aspect ratio: num/den (num)
        CAP_PROP_SAR_DEN       =41, //!< Sample aspect ratio: num/den (den)
-       CAP_PROP_BACKEND       =42, //!< current backend (enum VideoCaptureAPIs). Read-only property
+       CAP_PROP_BACKEND       =42, //!< Current backend (enum VideoCaptureAPIs). Read-only property
+       CAP_PROP_CHANNEL       =43, //!< Video input or Channel Number (only for those cameras that support)
 #ifndef CV_DOXYGEN
        CV__CAP_PROP_LATEST
 #endif

modules/videoio/test/test_camera.cpp

@@ -11,16 +11,8 @@
 
 namespace opencv_test { namespace {
 
-TEST(DISABLED_VideoIO_Camera, basic)
+static void test_readFrames(/*const*/ VideoCapture& capture, const int N = 100)
 {
-    VideoCapture capture(0);
-    ASSERT_TRUE(capture.isOpened());
-    std::cout << "Camera 0 via " << capture.getBackendName() << " backend" << std::endl;
-    std::cout << "Frame width: " << capture.get(CAP_PROP_FRAME_WIDTH) << std::endl;
-    std::cout << "     height: " << capture.get(CAP_PROP_FRAME_HEIGHT) << std::endl;
-    std::cout << "Capturing FPS: " << capture.get(CAP_PROP_FPS) << std::endl;
-
-    const int N = 100;
     Mat frame;
     int64 time0 = cv::getTickCount();
     for (int i = 0; i < N; i++)
@@ -34,7 +26,32 @@ TEST(DISABLED_VideoIO_Camera, basic)
     }
     int64 time1 = cv::getTickCount();
     printf("Processed %d frames on %.2f FPS\n", N, (N * cv::getTickFrequency()) / (time1 - time0 + 1));
+}
+
+TEST(DISABLED_VideoIO_Camera, basic)
+{
+    VideoCapture capture(0);
+    ASSERT_TRUE(capture.isOpened());
+    std::cout << "Camera 0 via " << capture.getBackendName() << " backend" << std::endl;
+    std::cout << "Frame width: " << capture.get(CAP_PROP_FRAME_WIDTH) << std::endl;
+    std::cout << "     height: " << capture.get(CAP_PROP_FRAME_HEIGHT) << std::endl;
+    std::cout << "Capturing FPS: " << capture.get(CAP_PROP_FPS) << std::endl;
+    test_readFrames(capture);
+    capture.release();
+}
 
+TEST(DISABLED_VideoIO_Camera, validate_V4L2_MJPEG)
+{
+    VideoCapture capture(CAP_V4L2);
+    ASSERT_TRUE(capture.isOpened());
+    ASSERT_TRUE(capture.set(CAP_PROP_FOURCC, VideoWriter::fourcc('M', 'J', 'P', 'G')));
+    std::cout << "Camera 0 via " << capture.getBackendName() << " backend" << std::endl;
+    std::cout << "Frame width: " << capture.get(CAP_PROP_FRAME_WIDTH) << std::endl;
+    std::cout << "     height: " << capture.get(CAP_PROP_FRAME_HEIGHT) << std::endl;
+    std::cout << "Capturing FPS: " << capture.get(CAP_PROP_FPS) << std::endl;
+    int fourcc = (int)capture.get(CAP_PROP_FOURCC);
+    std::cout << "FOURCC code: " << cv::format("0x%8x", fourcc) << std::endl;
+    test_readFrames(capture);
     capture.release();
 }