Add VTSupport for dynamically linking VideoToolbox.

content/common/gpu/media/vt_support.h

+// Copyright 2014 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.
+
+#ifndef CONTENT_COMMON_GPU_MEDIA_VT_SUPPORT_H_
+#define CONTENT_COMMON_GPU_MEDIA_VT_SUPPORT_H_
+
+#include <CoreFoundation/CoreFoundation.h>
+#include <CoreVideo/CVImageBuffer.h>
+
+#include "base/basictypes.h"
+
+template<typename T> struct DefaultSingletonTraits;
+
+// Declarations adapted from <CoreMedia/CoreMedia.h>
+typedef struct OpaqueCMBlockBuffer* CMBlockBufferRef;
+typedef struct OpaqueCMFormatDescription* CMFormatDescriptionRef;
+typedef struct OpaqueCMFormatDescription* CMVideoFormatDescriptionRef;
+typedef struct OpaqueCMSampleBuffer* CMSampleBufferRef;
+typedef uint32_t CMBlockBufferFlags;
+typedef int64_t CMItemCount;
+typedef OSStatus (*CMSampleBufferMakeDataReadyCallback)(
+    CMSampleBufferRef sbuf,
+    void *make_data_ready_refcon);
+
+struct CMBlockBufferCustomBlockSource;
+struct CMSampleTimingInfo;
+struct CMTime {

[mcasas, 2014/06/19 12:04:24]

This is also defined here:
https://code.google.com/p/chromium/codesearch#chromium/src/media/video/captur...

+  int64_t value;
+  int32_t timescale;
+  uint32_t flags;
+  int64_t epoch;
+};
+
+// Declarations adapted from <VideoToolbox/VideoToolbox.h>
+typedef struct OpaqueVTDecompressionSession* VTDecompressionSessionRef;
+typedef uint32_t VTDecodeFrameFlags;
+typedef uint32_t VTDecodeInfoFlags;
+typedef void (*VTDecompressionOutputCallback)(
+    void* decompression_output_refcon,
+    void* source_frame_refcon,
+    OSStatus status,
+    VTDecodeInfoFlags info_flags,
+    CVImageBufferRef image_buffer,
+    CMTime presentation_timestamp,
+    CMTime presentation_duration);
+
+struct VTDecompressionOutputCallbackRecord {
+  VTDecompressionOutputCallback decompression_output_callback;
+  void* decompression_output_refcon;
+};
+
+namespace content {
+
+// This Mac OS X-specific class provides dynamically-linked access to
+// CoreMedia and VideoToolbox, which are only available on 10.8 and later.
+class VTSupport {

[mcasas, 2014/06/19 12:04:24]

- Looking at src/media/video/capture/mac/, this class should be called
VideoToolboxGlue.

- There is already code in [1] for lazily loading and manipulating CoreMedia,
could we use it from here or refactor somehow?

- In [1] the idiom is a public CoreMediaGlue class offering data types and
static class methods and in the .mm file a singleton CoreMediaGlueInternal is
manipulated via lazy initialiser (good for startup time). Function pointer
typedefs and their pointer are not exposed. I think you should take the same
approach here for the VT parts.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/media/video/captur...

+ public:
+  // Returns an instance of the VTSupport class if the operating system supports
+  // it, NULL otherwise. It is safe to call this multiple times.
+  static VTSupport* GetInstance();
+
+  bool Initialized();
+
+  typedef OSStatus (*CMBlockBufferCreateWithMemoryBlockPtr)(
+      CFAllocatorRef structure_allocator,
+      void* memory_block,
+      size_t block_length,
+      CFAllocatorRef block_allocator,
+      const CMBlockBufferCustomBlockSource* custom_block_source,
+      size_t offset_to_data,
+      size_t data_length,
+      CMBlockBufferFlags flags,
+      CMBlockBufferRef* new_block_buffer_out);
+
+  typedef CFDictionaryRef (*CMFormatDescriptionGetExtensionsPtr)(
+      CMFormatDescriptionRef desc);
+
+  typedef OSStatus (*CMSampleBufferCreatePtr)(
+      CFAllocatorRef allocator,
+      CMBlockBufferRef data_buffer,
+      Boolean data_ready,
+      CMSampleBufferMakeDataReadyCallback make_data_ready_callback,
+      void* make_data_ready_refcon,
+      CMFormatDescriptionRef format_description,
+      CMItemCount num_samples,
+      CMItemCount num_sample_timing_entries,
+      const CMSampleTimingInfo* sample_timing_array,
+      CMItemCount num_sample_size_entries,
+      const size_t* sample_size_array,
+      CMSampleBufferRef* s_buf_out);
+
+  typedef OSStatus (*CMVideoFormatDescriptionCreateFromH264ParameterSetsPtr)(
+      CFAllocatorRef allocator,
+      size_t parameter_set_count,
+      const uint8_t* const* parameter_set_pointers,
+      const size_t* parameter_set_sizes,
+      int nal_unit_header_length,
+      CMFormatDescriptionRef *format_description_out);
+
+  typedef OSStatus (*VTDecompressionSessionCreatePtr)(
+      CFAllocatorRef allocator,
+      CMVideoFormatDescriptionRef video_format_description,
+      CFDictionaryRef video_decoder_specification,
+      CFDictionaryRef destination_image_buffer_attributes,
+      const VTDecompressionOutputCallbackRecord* output_callback,
+      VTDecompressionSessionRef* decompression_session_out);
+
+  typedef OSStatus (*VTDecompressionSessionDecodeFramePtr)(
+      VTDecompressionSessionRef session,
+      CMSampleBufferRef sample_buffer,
+      VTDecodeFrameFlags decode_flags,
+      void* source_frame_refcon,
+      VTDecodeInfoFlags* info_flags_out);
+
+  CMBlockBufferCreateWithMemoryBlockPtr CMBlockBufferCreateWithMemoryBlock;
+  CMFormatDescriptionGetExtensionsPtr CMFormatDescriptionGetExtensions;
+  CMSampleBufferCreatePtr CMSampleBufferCreate;
+  CMVideoFormatDescriptionCreateFromH264ParameterSetsPtr
+      CMVideoFormatDescriptionCreateFromH264ParameterSets;
+
+  VTDecompressionSessionDecodeFramePtr VTDecompressionSessionDecodeFrame;
+  VTDecompressionSessionCreatePtr VTDecompressionSessionCreate;
+
+ private:
+  VTSupport();
+  ~VTSupport();
+  void CloseLibraryHandles();
+
+  void* cm_handle_;
+  void* vt_handle_;
+  bool initialized_;
+
+  friend struct DefaultSingletonTraits<VTSupport>;
+  DISALLOW_COPY_AND_ASSIGN(VTSupport);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_MEDIA_VT_SUPPORT_H_