Merge pull request #11633 from alalek:issue_10546

modules/videoio/src/cap_v4l.cpp

@@ -265,8 +265,6 @@ struct buffer
     size_t  length;
 };
 
-static unsigned int n_buffers = 0;
-
 struct CvCaptureCAM_V4L CV_FINAL : public CvCapture
 {
     int deviceHandle;
@@ -347,43 +345,10 @@ static int    icvSetPropertyCAM_V4L( CvCaptureCAM_V4L* capture, int property_id,
 
 /***********************   Implementations  ***************************************/
 
-static int numCameras = 0;
-static int indexList = 0;
-
 CvCaptureCAM_V4L::~CvCaptureCAM_V4L() {
     icvCloseCAM_V4L(this);
 }
 
-/* Simple test program: Find number of Video Sources available.
-   Start from 0 and go to MAX_CAMERAS while checking for the device with that name.
-   If it fails on the first attempt of /dev/video0, then check if /dev/video is valid.
-   Returns the global numCameras with the correct value (we hope) */
-
-static void icvInitCapture_V4L() {
-   int deviceHandle;
-   int CameraNumber;
-   char deviceName[MAX_DEVICE_DRIVER_NAME];
-
-   CameraNumber = 0;
-   while(CameraNumber < MAX_CAMERAS) {
-      /* Print the CameraNumber at the end of the string with a width of one character */
-      sprintf(deviceName, "/dev/video%1d", CameraNumber);
-      /* Test using an open to see if this new device name really does exists. */
-      deviceHandle = open(deviceName, O_RDONLY);
-      if (deviceHandle != -1) {
-         /* This device does indeed exist - add it to the total so far */
-    // add indexList
-    indexList|=(1 << CameraNumber);
-        numCameras++;
-    }
-    if (deviceHandle != -1)
-      close(deviceHandle);
-    /* Set up to test the next /dev/video source in line */
-    CameraNumber++;
-   } /* End while */
-
-}; /* End icvInitCapture_V4L */
-
 static bool try_palette_v4l2(CvCaptureCAM_V4L* capture)
 {
     capture->form = v4l2_format();
@@ -690,7 +655,7 @@ static int _capture_V4L2 (CvCaptureCAM_V4L *capture)
 
     unsigned int buffer_number = capture->bufferSize;
 
-   try_again:
+try_again:
 
     capture->req.count = buffer_number;
     capture->req.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
@@ -726,7 +691,7 @@ static int _capture_V4L2 (CvCaptureCAM_V4L *capture)
         }
     }
 
-   for (n_buffers = 0; n_buffers < capture->req.count; ++n_buffers)
+    for (unsigned int n_buffers = 0; n_buffers < capture->req.count; ++n_buffers)
     {
         v4l2_buffer buf = v4l2_buffer();
         buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
@@ -785,39 +750,48 @@ static bool v4l2_reset( CvCaptureCAM_V4L* capture) {
 
 bool CvCaptureCAM_V4L::open(int _index)
 {
-   int autoindex = 0;
-   char _deviceName[MAX_DEVICE_DRIVER_NAME];
-
-   if (!numCameras)
-      icvInitCapture_V4L(); /* Haven't called icvInitCapture yet - do it now! */
-   if (!numCameras)
-     return false; /* Are there any /dev/video input sources? */
-
-   //search index in indexList
-   if ( (_index>-1) && ! ((1 << _index) & indexList) )
-   {
-     fprintf( stderr, "VIDEOIO ERROR: V4L: index %d is not correct!\n",_index);
-     return false; /* Did someone ask for not correct video source number? */
-   }
-
+    cv::String name;
     /* Select camera, or rather, V4L video source */
-   if (_index<0) { // Asking for the first device available
-     for (; autoindex<MAX_CAMERAS;autoindex++)
-    if (indexList & (1<<autoindex))
+    if (_index < 0) // Asking for the first device available
+    {
+        for (int autoindex = 0; autoindex < MAX_CAMERAS; ++autoindex)
+        {
+            name = cv::format("/dev/video%d", autoindex);
+            /* Test using an open to see if this new device name really does exists. */
+            int h = ::open(name.c_str(), O_RDONLY);
+            if (h != -1)
+            {
+                ::close(h);
+                _index = autoindex;
                 break;
-     if (autoindex==MAX_CAMERAS)
+            }
+        }
+        if (_index < 0)
+        {
+            fprintf(stderr, "VIDEOIO ERROR: V4L: can't find camera device\n");
+            name.clear();
             return false;
-     _index=autoindex;
-     autoindex++;// i can recall icvOpenCAM_V4l with index=-1 for next camera
+        }
+    }
+    else
+    {
+        name = cv::format("/dev/video%d", _index);
     }
 
     /* Print the CameraNumber at the end of the string with a width of one character */
-   sprintf(_deviceName, "/dev/video%1d", _index);
-   return open(_deviceName);
+    bool res = open(name.c_str());
+    if (!res)
+    {
+        fprintf(stderr, "VIDEOIO ERROR: V4L: can't open camera by index %d\n", _index);
+    }
+    return res;
 }
 
 bool CvCaptureCAM_V4L::open(const char* _deviceName)
 {
+#ifndef NDEBUG
+    fprintf(stderr, "(DEBUG) V4L: opening %s\n", _deviceName);
+#endif
     FirstCapture = 1;
     width = DEFAULT_V4L_WIDTH;
     height = DEFAULT_V4L_HEIGHT;
@@ -1014,13 +988,13 @@ move_411_block(int yTL, int yTR, int yBL, int yBR, int u, int v,
     int r, g, b;
 
     g = guScale * u + gvScale * v;
-//  if (force_rgb) {
-//      r = buScale * u;
-//      b = rvScale * v;
-//  } else {
+    //  if (force_rgb) {
+    //      r = buScale * u;
+    //      b = rvScale * v;
+    //  } else {
     r = rvScale * v;
     b = buScale * u;
-//  }
+    //  }
 
     yTL *= yScale; yTR *= yScale;
     yBL *= yScale; yBR *= yScale;
@@ -1325,7 +1299,7 @@ static int init_done = 0;
   Each entry at index x in the table represents the codeword
   present at the MSB of byte x.
 
-*/
+ */
 static void sonix_decompress_init(void)
 {
     int i;
@@ -1403,7 +1377,7 @@ static void sonix_decompress_init(void)
   Returns 0 if the operation was successful.
   Returns <0 if operation failed.
 
-*/
+ */
 static int sonix_decompress(int width, int height, unsigned char *inp, unsigned char *outp)
 {
     int row, col;
@@ -1859,13 +1833,13 @@ static void icvCloseCAM_V4L( CvCaptureCAM_V4L* capture ){
                 perror ("Unable to stop the stream");
             }
 
-       for (unsigned int n_buffers_ = 0; n_buffers_ < MAX_V4L_BUFFERS; ++n_buffers_)
+            for (unsigned int n_buffers = 0; n_buffers < MAX_V4L_BUFFERS; ++n_buffers)
             {
-           if (capture->buffers[n_buffers_].start) {
-               if (-1 == munmap (capture->buffers[n_buffers_].start, capture->buffers[n_buffers_].length)) {
+                if (capture->buffers[n_buffers].start) {
+                    if (-1 == munmap (capture->buffers[n_buffers].start, capture->buffers[n_buffers].length)) {
                         perror ("munmap");
                     } else {
-                   capture->buffers[n_buffers_].start = 0;
+                        capture->buffers[n_buffers].start = 0;
                     }
                 }
             }