Mac AVFoundation: use QTKit for cameras not working with AVF (Blackmagic).

media/video/capture/mac/video_capture_device_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/video/capture/mac/video_capture_device_mac.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/time/time.h"
 #import "media/video/capture/mac/avfoundation_glue.h"
 #import "media/video/capture/mac/platform_video_capturing_mac.h"
 #import "media/video/capture/mac/video_capture_device_avfoundation_mac.h"
 #import "media/video/capture/mac/video_capture_device_qtkit_mac.h"
 
 namespace media {
 
 const int kMinFrameRate = 1;
 const int kMaxFrameRate = 30;
 
-// In QT device identifiers, the USB VID and PID are stored in 4 bytes each.
+// In device identifiers, the USB VID and PID are stored in 4 bytes each.
 const size_t kVidPidSize = 4;
 
-struct Resolution {
-  int width;
-  int height;
-};
+// Some devices are not correctly supported in AVFoundation, f.i. Blackmagic,
+// see http://crbug.com/347371. The devices are identified by USB Vendor ID and
+// by a characteristic substring of the name, usually the vendor's name.
+const struct NameAndVid {
+  const char* vid;
+  const char* name;
+} kBlacklistedCameras[] = { { "a82c", "Blackmagic" } };
 
-const Resolution kQVGA = { 320, 240 },
-                 kVGA = { 640, 480 },
-                 kHD = { 1280, 720 };
+const struct Resolution {
+  const int width;
+  const int height;
+} kQVGA = { 320, 240 },
+  kVGA = { 640, 480 },
+  kHD = { 1280, 720 };
 
-const Resolution* const kWellSupportedResolutions[] = {
-   &kQVGA,
-   &kVGA,
-   &kHD,
+const struct Resolution* const kWellSupportedResolutions[] = {
+  &kQVGA,
+  &kVGA,
+  &kHD,
 };
 
 // Rescaling the image to fix the pixel aspect ratio runs the risk of making
 // the aspect ratio worse, if QTKit selects a new source mode with a different
-// shape.  This constant ensures that we don't take this risk if the current
+// shape. This constant ensures that we don't take this risk if the current
 // aspect ratio is tolerable.
 const float kMaxPixelAspectRatio = 1.15;
 
 // TODO(ronghuawu): Replace this with CapabilityList::GetBestMatchedCapability.
 void GetBestMatchSupportedResolution(int* width, int* height) {
   int min_diff = kint32max;
   int matched_width = *width;
   int matched_height = *height;
   int desired_res_area = *width * *height;
   for (size_t i = 0; i < arraysize(kWellSupportedResolutions); ++i) {
     int area = kWellSupportedResolutions[i]->width *
                kWellSupportedResolutions[i]->height;
     int diff = std::abs(desired_res_area - area);
     if (diff < min_diff) {
       min_diff = diff;
       matched_width = kWellSupportedResolutions[i]->width;
       matched_height = kWellSupportedResolutions[i]->height;
     }
   }
   *width = matched_width;
   *height = matched_height;
 }
 
+//static
 void VideoCaptureDevice::GetDeviceNames(Names* device_names) {
   // Loop through all available devices and add to |device_names|.
   device_names->clear();
 
   NSDictionary* capture_devices;
+  bool is_blacklisted_device = false;
   if (AVFoundationGlue::IsAVFoundationSupported()) {
     DVLOG(1) << "Enumerating video capture devices using AVFoundation";
     capture_devices = [VideoCaptureDeviceAVFoundation deviceNames];
+    std::string device_vid;
+    for (NSString* key in capture_devices) {

[Robert Sesek, 2014/04/10 17:49:10]

I'd maybe add some comments:

// Enumerate all the devices found by AVFoundation.

[mcasas, 2014/04/10 20:23:05]

Done.

+      Name name([[capture_devices valueForKey:key] UTF8String],
+          [key UTF8String], Name::AVFOUNDATION);
+      device_names->push_back(name);
+      device_vid = name.GetModel().substr(0, kVidPidSize);
+      // Compare the USB VendorID of the device to the blacklisted ones.

[Robert Sesek, 2014/04/10 17:49:10]

You're still adding blacklisted devices, though, right? So for a blacklisted
device, there will also be one with the same name prefixed with QTKit?

[mcasas, 2014/04/10 20:23:05]

Yes, exactly, point being that some resolutions of the blacklisted devices
work with AVFoundation.

+      for (size_t i = 0; i < arraysize(kBlacklistedCameras); ++i) {

[Robert Sesek, 2014/04/10 17:49:10]

// Find any blacklisted devices, and if there are some <answer to the question
above>.

[mcasas, 2014/04/10 20:23:05]

Done.

+        is_blacklisted_device |= (device_vid == kBlacklistedCameras[i].vid);
+        if (is_blacklisted_device)

[Robert Sesek, 2014/04/10 17:49:10]

Doesn't this mean if your blacklist has more than one device, and the user has
several blacklisted devices, only one will be blacklisted in practice?

[mcasas, 2014/04/10 20:23:05]

Wrong variable name, corrected to |is_any_device_blacklisted| .

The continue stops the comparison between the enumerated
device and the blacklisted devices, but does not prevent from
posterior device name comparisons. 

+          continue;
+      }
+    }
   } else {
     DVLOG(1) << "Enumerating video capture devices using QTKit";
     capture_devices = [VideoCaptureDeviceQTKit deviceNames];
+    for (NSString* key in capture_devices) {
+      Name name([[capture_devices valueForKey:key] UTF8String],
+          [key UTF8String], Name::QTKIT);
+      device_names->push_back(name);
+    }
   }
-  for (NSString* key in capture_devices) {
-    Name name([[capture_devices valueForKey:key] UTF8String],
-              [key UTF8String]);
-    device_names->push_back(name);
+
+  if (is_blacklisted_device) {

[Robert Sesek, 2014/04/10 17:49:10]

Since this only happens for AVFoundation, maybe fold it into that branch above?

[mcasas, 2014/04/10 20:23:05]

Done.

+    // Walk the QTKit device list and add those devices with a blacklisted name
+    // to the |device_names|, with a "QTKit" prefix to distinguish them from the
+    // AVFoundation ones.
+    capture_devices = [VideoCaptureDeviceQTKit deviceNames];
+    NSString* device_name;
+    for (NSString* key in capture_devices) {
+      device_name = [capture_devices valueForKey:key];
+      for (size_t i = 0; i < arraysize(kBlacklistedCameras); ++i) {
+        if ([device_name rangeOfString:@(kBlacklistedCameras[i].name)
+                               options:NSCaseInsensitiveSearch].length != 0) {
+          DVLOG(1) << "Enumerated blacklisted " << [device_name UTF8String];
+          Name name("QTKit " + std::string([device_name UTF8String]),

[Robert Sesek, 2014/04/10 17:49:10]

This string isn't visible anywhere, is it?

[mcasas, 2014/04/10 20:23:05]

This is the string that shows when clicking on the camera icon
inside the omnibox after a successful getUserMedia(), so is
shown to the user.

The blacklisted device is a fairly specialised and high end
one, needing external configuration and having all kinds of 
whistles and bells. Plus, the Blackmagic device is multiplexed
into a number of "virtual" devices (see the bug for the listing),
so the potential target user of this code is definitely camera 
savvy, hence I thought it fair to show both AVFoundation
naming and QTKit- preceded ones and let the user decide.

+              [key UTF8String], Name::QTKIT);
+          device_names->push_back(name);
+        }
+      }
+    }
   }
 }
 
 // static
 void VideoCaptureDevice::GetDeviceSupportedFormats(const Name& device,
     VideoCaptureFormats* formats) {
-  if (AVFoundationGlue::IsAVFoundationSupported()) {
+  if (device.capture_api_type() == Name::AVFOUNDATION) {
     DVLOG(1) << "Enumerating video capture capabilities, AVFoundation";
     [VideoCaptureDeviceAVFoundation getDevice:device
                              supportedFormats:formats];
   } else {
     NOTIMPLEMENTED();
   }
 }
 
 const std::string VideoCaptureDevice::Name::GetModel() const {
   // Both PID and VID are 4 characters.
@@ skipping 113 matching lines @@
   Names device_names;
   GetDeviceNames(&device_names);
   Names::iterator it = device_names.begin();
   for (; it != device_names.end(); ++it) {
     if (it->id() == device_name_.id())
       break;
   }
   if (it == device_names.end())
     return false;
 
-  if (AVFoundationGlue::IsAVFoundationSupported()) {
+  DCHECK_NE(it->capture_api_type(), Name::API_TYPE_UNKNOWN);
+  if (it->capture_api_type() == Name::AVFOUNDATION) {
     capture_device_ =
         [[VideoCaptureDeviceAVFoundation alloc] initWithFrameReceiver:this];
   } else {
     capture_device_ =
         [[VideoCaptureDeviceQTKit alloc] initWithFrameReceiver:this];
   }
 
   if (!capture_device_)
     return false;
 
@@ skipping 101 matching lines @@
  if (![capture_device_ setCaptureHeight:capture_format_.frame_size.height()
                                   width:capture_format_.frame_size.width()
                               frameRate:capture_format_.frame_rate]) {
    ReceiveError("Could not configure capture device.");
    return false;
  }
  return true;
 }
 
 } // namespace media