diff --git a/modules/videoio/src/cap_v4l.cpp b/modules/videoio/src/cap_v4l.cpp index 4f00e43d51..fc9f6e06a8 100644 --- a/modules/videoio/src/cap_v4l.cpp +++ b/modules/videoio/src/cap_v4l.cpp @@ -294,6 +294,9 @@ typedef struct CvCaptureCAM_V4L int index; int width, height; __u32 fps; + bool convert_rgb; + bool frame_allocated; + /* V4L2 variables */ buffer buffers[MAX_V4L_BUFFERS + 1]; struct v4l2_capability cap; @@ -674,6 +677,43 @@ static int v4l2_set_fps(CvCaptureCAM_V4L* capture) { return ioctl (capture->deviceHandle, VIDIOC_S_PARM, &setfps); } +static int v4l2_num_channels(__u32 palette) { + switch(palette) { + case V4L2_PIX_FMT_MJPEG: + case V4L2_PIX_FMT_JPEG: + return 1; + case V4L2_PIX_FMT_YUYV: + case V4L2_PIX_FMT_UYVY: + return 2; + default: + return 0; + } +} + +static void v4l2_create_frame(CvCaptureCAM_V4L *capture) { + CvSize size(capture->form.fmt.pix.width, capture->form.fmt.pix.height); + int channels = 3; + + if (!capture->convert_rgb) { + if (capture->palette == V4L2_PIX_FMT_MJPEG || capture->palette == V4L2_PIX_FMT_JPEG) { + size = CvSize(capture->buffers[capture->bufferIndex].length, 1); + } + channels = v4l2_num_channels(capture->palette); + } + + /* Set up Image data */ + cvInitImageHeader(&capture->frame, size, IPL_DEPTH_8U, channels); + + /* Allocate space for pixelformat we convert to. + * If we do not convert frame is just points to the buffer + */ + if(capture->convert_rgb) { + capture->frame.imageData = (char*)cvAlloc(capture->frame.imageSize); + } + + capture->frame_allocated = capture->convert_rgb; +} + static int _capture_V4L2 (CvCaptureCAM_V4L *capture) { char deviceName[MAX_DEVICE_DRIVER_NAME]; @@ -829,13 +869,7 @@ static int _capture_V4L2 (CvCaptureCAM_V4L *capture) } } - /* Set up Image data */ - cvInitImageHeader( &capture->frame, - cvSize( capture->form.fmt.pix.width, - capture->form.fmt.pix.height ), - IPL_DEPTH_8U, 3, IPL_ORIGIN_TL, 4 ); - /* Allocate space for RGBA data */ - capture->frame.imageData = (char *)cvAlloc(capture->frame.imageSize); + v4l2_create_frame(capture); // reinitialize buffers capture->FirstCapture = 1; @@ -1022,6 +1056,7 @@ static CvCaptureCAM_V4L * icvCaptureFromCAM_V4L (int index) capture->width = DEFAULT_V4L_WIDTH; capture->height = DEFAULT_V4L_HEIGHT; capture->fps = DEFAULT_V4L_FPS; + capture->convert_rgb = true; if (_capture_V4L2 (capture) == -1) { icvCloseCAM_V4L(capture); @@ -1939,18 +1974,16 @@ static int sonix_decompress(int width, int height, unsigned char *inp, unsigned static IplImage* icvRetrieveFrameCAM_V4L( CvCaptureCAM_V4L* capture, int) { #ifdef HAVE_CAMV4L2 - if (V4L2_SUPPORT == 0) -#endif /* HAVE_CAMV4L2 */ #ifdef HAVE_CAMV4L + if (V4L2_SUPPORT == 0) { - /* [FD] this really belongs here */ if (ioctl(capture->deviceHandle, VIDIOCSYNC, &capture->mmaps[capture->bufferIndex].frame) == -1) { fprintf( stderr, "VIDEOIO ERROR: V4L: Could not SYNC to video stream. %s\n", strerror(errno)); } - } #endif /* HAVE_CAMV4L */ +#endif /* HAVE_CAMV4L2 */ /* Now get what has already been captured as a IplImage return */ @@ -1960,15 +1993,19 @@ static IplImage* icvRetrieveFrameCAM_V4L( CvCaptureCAM_V4L* capture, int) { if (V4L2_SUPPORT == 1) { + // we need memory iff convert_rgb is true + bool recreate_frame = capture->frame_allocated != capture->convert_rgb; - if(((unsigned long)capture->frame.width != capture->form.fmt.pix.width) - || ((unsigned long)capture->frame.height != capture->form.fmt.pix.height)) { - cvFree(&capture->frame.imageData); - cvInitImageHeader( &capture->frame, - cvSize( capture->form.fmt.pix.width, - capture->form.fmt.pix.height ), - IPL_DEPTH_8U, 3, IPL_ORIGIN_TL, 4 ); - capture->frame.imageData = (char *)cvAlloc(capture->frame.imageSize); + if (!capture->convert_rgb) { + // for mjpeg streams the size might change in between, so we have to change the header + recreate_frame += capture->frame.imageSize != (int)capture->buffers[capture->bufferIndex].length; + } + + if(recreate_frame) { + // printf("realloc %d %zu\n", capture->frame.imageSize, capture->buffers[capture->bufferIndex].length); + if(capture->frame_allocated) + cvFree(&capture->frame.imageData); + v4l2_create_frame(capture); } } @@ -1996,6 +2033,11 @@ static IplImage* icvRetrieveFrameCAM_V4L( CvCaptureCAM_V4L* capture, int) { if (V4L2_SUPPORT == 1) { + if(!capture->convert_rgb) { + capture->frame.imageData = (char*)capture->buffers[capture->bufferIndex].start; + return &capture->frame; + } + switch (capture->palette) { case V4L2_PIX_FMT_BGR24: @@ -2174,6 +2216,8 @@ static double icvGetPropertyCAM_V4L (CvCaptureCAM_V4L* capture, return capture->palette; case CV_CAP_PROP_FORMAT: return CV_8UC3; + case CV_CAP_PROP_CONVERT_RGB: + return capture->convert_rgb; } if(property_id == CV_CAP_PROP_FPS) { @@ -2416,10 +2460,8 @@ static int icvSetControl (CvCaptureCAM_V4L* capture, static int icvSetPropertyCAM_V4L( CvCaptureCAM_V4L* capture, int property_id, double value ){ static int width = 0, height = 0; - int retval; - - /* initialization */ - retval = 0; + int retval = 0; + bool possible; /* two subsequent calls setting WIDTH and HEIGHT will change the video size */ @@ -2447,6 +2489,12 @@ static int icvSetPropertyCAM_V4L( CvCaptureCAM_V4L* capture, capture->fps = value; retval = v4l2_reset( capture); break; + case CV_CAP_PROP_CONVERT_RGB: + // returns "0" for formats we do not know how to map to IplImage + possible = v4l2_num_channels(capture->palette); + capture->convert_rgb = bool(value) && possible; + retval = !possible && bool(value) ? -1 : 0; + break; default: retval = icvSetControl(capture, property_id, value); break; diff --git a/samples/python2/video_v4l2.py b/samples/python2/video_v4l2.py new file mode 100644 index 0000000000..0f03e6bf00 --- /dev/null +++ b/samples/python2/video_v4l2.py @@ -0,0 +1,64 @@ +#!/usr/bin/env python + +''' +VideoCapture sample showcasing some features of the Video4Linux2 backend + +Sample shows how VideoCapture class can be used to control parameters +of a webcam such as focus or framerate. +Also the sample provides an example how to access raw images delivered +by the hardware to get a grayscale image in a very efficient fashion. + +Keys: + ESC - exit + g - toggle optimized grayscale conversion + +''' + +import cv2 + +def decode_fourcc(v): + v = int(v) + return "".join([chr((v >> 8 * i) & 0xFF) for i in range(4)]) + +font = cv2.FONT_HERSHEY_SIMPLEX +color = (0, 255, 0) + +cap = cv2.VideoCapture(0) +cap.set(cv2.CAP_PROP_AUTOFOCUS, False) + +cv2.namedWindow("Video") + +convert_rgb = True +fps = int(cap.get(cv2.CAP_PROP_FPS)) +focus = int(cap.get(cv2.CAP_PROP_FOCUS)) * 100 + +cv2.createTrackbar("FPS", "Video", fps, 30, lambda v: cap.set(cv2.CAP_PROP_FPS, v)) +cv2.createTrackbar("Focus", "Video", focus, 100, lambda v: cap.set(cv2.CAP_PROP_FOCUS, v / 100)) + +while True: + status, img = cap.read() + + fourcc = decode_fourcc(cap.get(cv2.CAP_PROP_FOURCC)) + + fps = cap.get(cv2.CAP_PROP_FPS) + + if not bool(cap.get(cv2.CAP_PROP_CONVERT_RGB)): + if fourcc == "MJPG": + img = cv2.imdecode(img, cv2.IMREAD_GRAYSCALE) + elif fourcc == "YUYV": + img = cv2.cvtColor(img, cv2.COLOR_YUV2GRAY_YUYV) + else: + print("unsupported format") + break + + cv2.putText(img, "Mode: {}".format(fourcc), (15, 40), font, 1.0, color) + cv2.putText(img, "FPS: {}".format(fps), (15, 80), font, 1.0, color) + cv2.imshow("Video", img) + + k = cv2.waitKey(1) + + if k == 27: + break + elif k == ord("g"): + convert_rgb = not convert_rgb + cap.set(cv2.CAP_PROP_CONVERT_RGB, convert_rgb)