While that's not the cause of this issue (camera quits streaming), your note got me looking at the read_frame code.

I'd had a code fragment that just ignored the frame (by re-queuing without processing it) when it didn't match the expected frame size. However, that code was for a specific camera resolution and needed changing for the camera I'm testing with now.

But, the hang occurs immediately after receiving frames of the expected size. I fixedthe code that ignores frames with unexpected buffer sizes, but it never executes even when I see the hangs. So, that's not what's causing this issue.

But thanks for the good suggestion! It lead me to fix what would have been a nasty bug.

Code for read_frame:

Qt Code: 
  1. int CameraInterface::read_frame(int)
  2. {
  3.    struct v4l2_buffer buf;
  4.    unsigned int i;
  5.    //qDebug() << frames_read++;
  6.    if (testing_only) return 0;
  7.  
  8.  
  9.    if (!stream_forever && frames_read >= frame_count)
  10.    {
  11.        qDebug() << "frame count exceeded";
  12.        emit frames_done();
  13.        return 0;
  14.    }
  15.  
  16.    switch (io)
  17.    {
  18.   .....
  19.  
  20.    case IO_METHOD_MMAP:
  21.       CLEAR(buf);
  22.  
  23.       buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
  24.       buf.memory = V4L2_MEMORY_MMAP;
  25.  
  26.       if (-1 == xioctl(fd, VIDIOC_DQBUF, &buf))
  27.       {
  28.          switch (errno)
  29.          {
  30.          case EAGAIN:
  31.             return 0;
  32.  
  33.          case EIO:
  34.             /* Could ignore EIO, see spec. */
  35.  
  36.             /* fall through */
  37.  
  38.          default:
  39.             errno_exit("VIDIOC_DQBUF");
  40.          }
  41.       }
  42. #if 0
  43.       qDebug() << "frames read: " << frames_read++;
  44.       if (frames_read % 2)
  45.       {
  46.           qDebug() << "skipping frame";
  47.              xioctl(fd, VIDIOC_QBUF, &buf);
  48.              return 1;
  49.       }
  50. #endif
  51.       frameQueued = false;
  52.       assert(buf.index < n_buffers);
  53.  
  54.       qDebug() << "\t\t\tframe DQ'ed, bytes " << buf.bytesused << "buffers = " << n_buffers;
  55.       if (buf.bytesused != 921600)
  56.       {
  57.           qDebug() << "partial frame";
  58.           xioctl(fd, VIDIOC_QBUF, &buf);
  59.           frameQueued = true;
  60.           qDebug() << "Unexpected framesize" << buf.bytesused;
  61.           //exit(-1);
  62.       }
  63.       /*
  64.       if (!colorCamera && buf.bytesused < 1843200)
  65.       {
  66.           xioctl(fd, VIDIOC_QBUF, &buf);
  67.           frameQueued = true;
  68.           qDebug() << "Partial frame" << buf.bytesused;
  69.       }
  70.       */
  71.       else
  72.       {
  73.  
  74.           emit frameReady(buffers[buf.index].start,buf.bytesused);
  75.  
  76.           // when streaming expect client to send message to queue next frame
  77.           // otherwise, we know there's been  seconds for client to process frame
  78.           // setup = false;
  79.           if (!setup)
  80.           {
  81.               xioctl(fd, VIDIOC_QBUF, &buf);
  82.               frameQueued=true;
  83.           }
  84.       }
  85.  
  86.       break;
  87.  
  88. ...
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