Sandbox initialization for VideoToolbox.

content/common/gpu/media/vt_video_decode_accelerator.cc

Index: content/common/gpu/media/vt_video_decode_accelerator.cc
diff --git a/content/common/gpu/media/vt_video_decode_accelerator.cc b/content/common/gpu/media/vt_video_decode_accelerator.cc
index 1cae8f255a43e391096088d820713abd00400fcf..6f1e18ab86bf9da90cf7a62d96a927ada372ca3f 100644
--- a/content/common/gpu/media/vt_video_decode_accelerator.cc
+++ b/content/common/gpu/media/vt_video_decode_accelerator.cc
@@ -38,6 +38,121 @@ static const int kNALUHeaderLength = 4;
 // requirements are low, as we don't need the textures to be backed by storage.
 static const int kNumPictureBuffers = media::limits::kMaxVideoFrames + 1;
 
+// Build an |image_config| dictionary for VideoToolbox initialization.
+static CFMutableDictionaryRef BuildImageConfig(
+    CMVideoDimensions coded_dimensions) {
+  // TODO(sandersd): RGBA option for 4:4:4 video.
+  int32_t pixel_format = kCVPixelFormatType_422YpCbCr8;
+
+#define CFINT(i) CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &i)
+  base::ScopedCFTypeRef<CFNumberRef> cf_pixel_format(CFINT(pixel_format));
+  base::ScopedCFTypeRef<CFNumberRef> cf_width(CFINT(coded_dimensions.width));
+  base::ScopedCFTypeRef<CFNumberRef> cf_height(CFINT(coded_dimensions.height));
+#undef CFINT
+
+  CFMutableDictionaryRef image_config = CFDictionaryCreateMutable(
+      kCFAllocatorDefault,
+      4,  // capacity
+      &kCFTypeDictionaryKeyCallBacks,
+      &kCFTypeDictionaryValueCallBacks);
+  CFDictionarySetValue(image_config, kCVPixelBufferPixelFormatTypeKey,
+                       cf_pixel_format);
+  CFDictionarySetValue(image_config, kCVPixelBufferWidthKey, cf_width);
+  CFDictionarySetValue(image_config, kCVPixelBufferHeightKey, cf_height);
+  CFDictionarySetValue(image_config, kCVPixelBufferOpenGLCompatibilityKey,
+                       kCFBooleanTrue);
+
+  return image_config;
+}
+
+// The purpose of this function is to preload the generic and hardware-specific
+// libraries required by VideoToolbox before the GPU sandbox is enabled.
+// VideoToolbox normally loads the hardware-specific libraries lazily, so we
+// must actually create a decompression session.
+//
+// If creating a decompression session fails, hardware decoding will be disabled
+// (Initialize() will always return false). If it succeeds but a required
+// library is not loaded yet (I have not experienced this, but the details are
+// not documented), then VideoToolbox will fall back on software decoding

[DaleCurtis, 2014/11/21 21:00:49]

Is there a way you record when this happens as a UMA statistic? Otherwise it
seems this could happen and we'd never know.

[sandersd (OOO until July 31), 2014/11/21 21:20:19]

It's possible, but is also expected when the resolution changes below the
hardware decoder's limit. A better solution is to require hardware decoding and
fail otherwise, but we can't do that until fallback to Chromium's software path
works smoothly. (That is what RequireHardwareAcceleratedVideoDecoder configures;
I don't use it in the regular initialization path though.)

+// internally. If that happens, the likely solution is to expand the scope of
+// this initialization.
+void InitializeVideoToolbox() {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kDisableAcceleratedVideoDecode)) {
+    return;
+  }
+
+  if (!IsVtInitialized()) {
+    // CoreVideo is also required, but the loader stops after the first path is
+    // loaded. Instead we rely on the transitive dependency from VideoToolbox to
+    // CoreVideo.
+    // TODO(sandersd): Fallback to PrivateFrameworks.
+    StubPathMap paths;
+    paths[kModuleVt].push_back(FILE_PATH_LITERAL(
+        "/System/Library/Frameworks/VideoToolbox.framework/VideoToolbox"));
+    if (!InitializeStubs(paths))
+      return;
+  }
+
+  // Create a decoding session.
+  // SPS and PPS data were taken from the 480p encoding of Big Buck Bunny.
+  const uint8_t sps[] = {0x67, 0x64, 0x00, 0x1e, 0xac, 0xd9, 0x80, 0xd4, 0x3d,
+                         0xa1, 0x00, 0x00, 0x03, 0x00, 0x01, 0x00, 0x00, 0x03,
+                         0x00, 0x30, 0x8f, 0x16, 0x2d, 0x9a};
+  const uint8_t pps[] = {0x68, 0xe9, 0x7b, 0xcb};
+  const uint8_t* data_ptrs[] = {sps, pps};
+  const size_t data_sizes[] = {arraysize(sps), arraysize(pps)};
+
+  base::ScopedCFTypeRef<CMFormatDescriptionRef> format;
+  OSStatus status = CMVideoFormatDescriptionCreateFromH264ParameterSets(
+      kCFAllocatorDefault,
+      2,                          // parameter_set_count
+      data_ptrs,                  // &parameter_set_pointers
+      data_sizes,                 // &parameter_set_sizes
+      kNALUHeaderLength,          // nal_unit_header_length
+      format.InitializeInto());
+  if (status) {
+    LOG(ERROR) << "Failed to create CMVideoFormatDescription while "

[DaleCurtis, 2014/11/21 21:00:49]

Check out OSSTATUS_LOG and OSSTATUS_DLOG. You can see example using in
audio_manager_mac.  I take it you're intentionally using LOG here?

[sandersd (OOO until July 31), 2014/11/21 21:20:19]

Done.

+               << "initializing VideoToolbox";
+    content_common_gpu_media::UninitializeVt();
+    return;
+  }
+
+  base::ScopedCFTypeRef<CFMutableDictionaryRef> decoder_config(
+      CFDictionaryCreateMutable(
+          kCFAllocatorDefault,
+          1,  // capacity
+          &kCFTypeDictionaryKeyCallBacks,
+          &kCFTypeDictionaryValueCallBacks));
+
+  CFDictionarySetValue(
+      decoder_config,
+      // kVTVideoDecoderSpecification_RequireHardwareAcceleratedVideoDecoder
+      CFSTR("RequireHardwareAcceleratedVideoDecoder"),
+      kCFBooleanTrue);
+
+  base::ScopedCFTypeRef<CFMutableDictionaryRef> image_config(
+      BuildImageConfig(CMVideoFormatDescriptionGetDimensions(format)));
+
+  VTDecompressionOutputCallbackRecord callback;

[DaleCurtis, 2014/11/21 21:00:49]

Worth using = {0} to zero all potential fields?

[sandersd (OOO until July 31), 2014/11/21 21:20:19]

Done. (Although the regular path does not do this.)

+  callback.decompressionOutputCallback = NULL;
+  callback.decompressionOutputRefCon = NULL;
+
+  base::ScopedCFTypeRef<VTDecompressionSessionRef> session;
+  status = VTDecompressionSessionCreate(
+      kCFAllocatorDefault,
+      format,               // video_format_description
+      decoder_config,       // video_decoder_specification
+      image_config,         // destination_image_buffer_attributes
+      &callback,            // output_callback
+      session.InitializeInto());
+  if (status) {
+    LOG(ERROR) << "Initializing VideoToolbox failed with status " << status;
+    content_common_gpu_media::UninitializeVt();
+    return;
+  }

[DaleCurtis, 2014/11/21 21:00:49]

Is the session automatically dropped once all refs are lost? Do you need to
close it cleanly?  I see a VTDecompressionSessionInvalidate() method...

[sandersd (OOO until July 31), 2014/11/21 21:20:19]

It is, VTDecompressionSessionInvalidate() just lets you do it earlier.

+}
+
 // Route decoded frame callbacks back into the VTVideoDecodeAccelerator.
 static void OutputThunk(
     void* decompression_output_refcon,
@@ -92,27 +207,13 @@ bool VTVideoDecodeAccelerator::Initialize(
   DCHECK(gpu_thread_checker_.CalledOnValidThread());
   client_ = client;
 
-  // Only H.264 is supported.
-  if (profile < media::H264PROFILE_MIN || profile > media::H264PROFILE_MAX)
+  if (!IsVtInitialized())
     return false;
 
-  // Require --no-sandbox until VideoToolbox library loading is part of sandbox
-  // startup (and this VDA is ready for regular users).
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kNoSandbox))
+  // Only H.264 is supported.
+  if (profile < media::H264PROFILE_MIN || profile > media::H264PROFILE_MAX)
     return false;
 
-  if (!IsVtInitialized()) {
-    // CoreVideo is also required, but the loader stops after the first
-    // path is loaded. Instead we rely on the transitive dependency from
-    // VideoToolbox to CoreVideo.
-    // TODO(sandersd): Fallback to PrivateFrameworks for VideoToolbox.
-    StubPathMap paths;
-    paths[kModuleVt].push_back(FILE_PATH_LITERAL(
-        "/System/Library/Frameworks/VideoToolbox.framework/VideoToolbox"));
-    if (!InitializeStubs(paths))
-      return false;
-  }
-
   // Spawn a thread to handle parsing and calling VideoToolbox.
   if (!decoder_thread_.Start())
     return false;
@@ -193,25 +294,7 @@ bool VTVideoDecodeAccelerator::ConfigureDecoder() {
       kCFBooleanTrue);
 
   base::ScopedCFTypeRef<CFMutableDictionaryRef> image_config(
-      CFDictionaryCreateMutable(
-          kCFAllocatorDefault,
-          4,  // capacity
-          &kCFTypeDictionaryKeyCallBacks,
-          &kCFTypeDictionaryValueCallBacks));
-
-#define CFINT(i) CFNumberCreate(kCFAllocatorDefault, kCFNumberSInt32Type, &i)
-  // TODO(sandersd): RGBA option for 4:4:4 video.
-  int32_t pixel_format = kCVPixelFormatType_422YpCbCr8;
-  base::ScopedCFTypeRef<CFNumberRef> cf_pixel_format(CFINT(pixel_format));
-  base::ScopedCFTypeRef<CFNumberRef> cf_width(CFINT(coded_dimensions.width));
-  base::ScopedCFTypeRef<CFNumberRef> cf_height(CFINT(coded_dimensions.height));
-#undef CFINT
-  CFDictionarySetValue(
-      image_config, kCVPixelBufferPixelFormatTypeKey, cf_pixel_format);
-  CFDictionarySetValue(image_config, kCVPixelBufferWidthKey, cf_width);
-  CFDictionarySetValue(image_config, kCVPixelBufferHeightKey, cf_height);
-  CFDictionarySetValue(
-      image_config, kCVPixelBufferOpenGLCompatibilityKey, kCFBooleanTrue);
+      BuildImageConfig(coded_dimensions));
 
   // TODO(sandersd): Does the old session need to be flushed first?
   session_.reset();