To enumerate webcams on Linux more robustically

BUG=178359
TEST=media_unittests

Review URL: https://chromiumcodereview.appspot.com/13056002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@192048 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 28 insertions, 41 deletions

diff --git a/media/video/capture/linux/video_capture_device_linux.cc b/media/video/capture/linux/video_capture_device_linux.cc
index 3350867..e47eac3 100644
--- a/media/video/capture/linux/video_capture_device_linux.cc
+++ b/media/video/capture/linux/video_capture_device_linux.cc
@@ -21,20 +21,6 @@
 #include "base/file_util.h"
 #include "base/stringprintf.h"
 
-// Workaround for some device. This query of all controls magically brings
-// device back to normal from bad state.
-// See http://crbug.com/94134.
-static void ResetCameraByEnumeratingIoctlsHACK(int fd) {
-  struct v4l2_queryctrl query_ctrl;
-  memset(&query_ctrl, 0, sizeof(query_ctrl));
-
-  for (query_ctrl.id = V4L2_CID_BASE;
-       query_ctrl.id < V4L2_CID_LASTP1;
-       query_ctrl.id++) {
-    ioctl(fd, VIDIOC_QUERYCTRL, &query_ctrl);
-  }
-}
-
 namespace media {
 
 // Max number of video buffers VideoCaptureDeviceLinux can allocate.
@@ -67,7 +53,9 @@ static VideoCaptureCapability::Format V4l2ColorToVideoCaptureColorFormat(
       result = VideoCaptureCapability::kYUY2;
       break;
     case V4L2_PIX_FMT_MJPEG:
+    case V4L2_PIX_FMT_JPEG:
       result = VideoCaptureCapability::kMJPEG;
+      break;
   }
   DCHECK_NE(result, VideoCaptureCapability::kColorUnknown);
   return result;
@@ -80,6 +68,10 @@ static void GetListOfUsableFourCCs(bool favour_mjpeg, std::list<int>* fourccs) {
     fourccs->push_front(V4L2_PIX_FMT_MJPEG);
   else
     fourccs->push_back(V4L2_PIX_FMT_MJPEG);
+
+  // JPEG works as MJPEG on some gspca webcams from field reports.
+  // Put it as the least preferred format.
+  fourccs->push_back(V4L2_PIX_FMT_JPEG);
 }
 
 static bool HasUsableFormats(int fd) {
@@ -257,42 +249,37 @@ void VideoCaptureDeviceLinux::OnAllocate(int width,
     return;
   }
 
-  v4l2_format video_fmt;
-  memset(&video_fmt, 0, sizeof(video_fmt));
-  video_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-  video_fmt.fmt.pix.sizeimage = 0;
-  video_fmt.fmt.pix.width = width;
-  video_fmt.fmt.pix.height = height;
-
-  // Some device failed in first VIDIOC_TRY_FMT with EBUSY or EIO.
-  // But second VIDIOC_TRY_FMT succeeds.
-  // See http://crbug.com/94134.
-  bool format_match = false;
-  std::list<int> v4l2_formats;
-
+  // Get supported video formats in preferred order.
   // For large resolutions, favour mjpeg over raw formats.
+  std::list<int> v4l2_formats;
   GetListOfUsableFourCCs(width > kMjpegWidth || height > kMjpegHeight,
                          &v4l2_formats);
 
-  for (std::list<int>::const_iterator it = v4l2_formats.begin();
-       it != v4l2_formats.end() && !format_match; ++it) {
-    video_fmt.fmt.pix.pixelformat = *it;
-    for (int attempt = 0; attempt < 2 && !format_match; ++attempt) {
-      ResetCameraByEnumeratingIoctlsHACK(device_fd_);
-      if (ioctl(device_fd_, VIDIOC_TRY_FMT, &video_fmt) < 0) {
-        if (errno != EIO)
-          break;
-      } else {
-        format_match = true;
-      }
-    }
+  v4l2_fmtdesc fmtdesc;
+  memset(&fmtdesc, 0, sizeof(v4l2_fmtdesc));
+  fmtdesc.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+
+  // Enumerate image formats.
+  std::list<int>::iterator best = v4l2_formats.end();
+  while (ioctl(device_fd_, VIDIOC_ENUM_FMT, &fmtdesc) == 0) {
+    best = std::find(v4l2_formats.begin(), best, fmtdesc.pixelformat);
+    fmtdesc.index++;
   }
 
-  if (!format_match) {
-    SetErrorState("Failed to find supported camera format.");
+  if (best == v4l2_formats.end()) {
+    SetErrorState("Failed to find a supported camera format.");
     return;
   }
+
   // Set format and frame size now.
+  v4l2_format video_fmt;
+  memset(&video_fmt, 0, sizeof(video_fmt));
+  video_fmt.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+  video_fmt.fmt.pix.sizeimage = 0;
+  video_fmt.fmt.pix.width = width;
+  video_fmt.fmt.pix.height = height;
+  video_fmt.fmt.pix.pixelformat = *best;
+
   if (ioctl(device_fd_, VIDIOC_S_FMT, &video_fmt) < 0) {
     SetErrorState("Failed to set camera format");
     return;