[cast] Add optional VideoEncoder method to flush frames.

media/cast/sender/h264_vt_encoder.cc

Index: media/cast/sender/h264_vt_encoder.cc
diff --git a/media/cast/sender/h264_vt_encoder.cc b/media/cast/sender/h264_vt_encoder.cc
index 33923488c51daa96b99847893ea713204588837c..d740b8026d1f463bd36346b801f00e16bbb83a68 100644
--- a/media/cast/sender/h264_vt_encoder.cc
+++ b/media/cast/sender/h264_vt_encoder.cc
@@ -11,6 +11,7 @@
 #include "base/bind_helpers.h"
 #include "base/location.h"
 #include "base/logging.h"
+#include "base/macros.h"
 #include "media/base/mac/corevideo_glue.h"
 #include "media/base/mac/video_frame_mac.h"
 #include "media/cast/sender/video_frame_factory.h"
@@ -43,6 +44,21 @@ base::ScopedCFTypeRef<CFDictionaryRef> DictionaryWithKeyValue(CFTypeRef key,
       &kCFTypeDictionaryValueCallBacks));
 }
 
+base::ScopedCFTypeRef<CFArrayRef> ArrayWithIntegers(const std::vector<int>& v) {
+  std::vector<CFNumberRef> numbers;
+  numbers.reserve(v.size());
+  for (const int i : v) {
+    numbers.push_back(CFNumberCreate(nullptr, kCFNumberSInt32Type, &i));
+  }
+  base::ScopedCFTypeRef<CFArrayRef> array(CFArrayCreate(
+      kCFAllocatorDefault, reinterpret_cast<const void**>(&numbers[0]),
+      numbers.size(), &kCFTypeArrayCallBacks));
+  for (CFNumberRef number : numbers) {
+    CFRelease(number);
+  }
+  return array;
+}
+
 template <typename NalSizeType>
 void CopyNalsToAnnexB(char* avcc_buffer,
                       const size_t avcc_size,
@@ -257,11 +273,20 @@ bool H264VideoToolboxEncoder::Initialize(
       kCFBooleanTrue);
 #endif
 
+  // Certain encoders prefer kCVPixelFormatType_422YpCbCr8, which is not
+  // supported through VideoFrame. We can force 420 formats to be used instead.
+  const int formats[] = {
+      kCVPixelFormatType_420YpCbCr8Planar,
+      CoreVideoGlue::kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange};
+  base::ScopedCFTypeRef<CFArrayRef> formats_array = ArrayWithIntegers(
+      std::vector<int>(formats, formats + arraysize(formats)));
+  base::ScopedCFTypeRef<CFDictionaryRef> buffer_attributes =
+      DictionaryWithKeyValue(kCVPixelBufferPixelFormatTypeKey, formats_array);
+
   VTCompressionSessionRef session;
   OSStatus status = videotoolbox_glue_->VTCompressionSessionCreate(
       kCFAllocatorDefault, video_config.width, video_config.height,
-      CoreMediaGlue::kCMVideoCodecType_H264, encoder_spec,
-      nullptr /* sourceImageBufferAttributes */,
+      CoreMediaGlue::kCMVideoCodecType_H264, encoder_spec, buffer_attributes,
       nullptr /* compressedDataAllocator */,
       &H264VideoToolboxEncoder::CompressionCallback,
       reinterpret_cast<void*>(this), &session);
@@ -309,6 +334,11 @@ void H264VideoToolboxEncoder::ConfigureSession(
   SetSessionProperty(
       videotoolbox_glue_->kVTCompressionPropertyKey_YCbCrMatrix(),
       kCVImageBufferYCbCrMatrix_ITU_R_709_2);
+  if (video_config.max_number_of_video_buffers_used > 0) {
+    SetSessionProperty(
+        videotoolbox_glue_->kVTCompressionPropertyKey_MaxFrameDelayCount(),
+        video_config.max_number_of_video_buffers_used);

[miu, 2015/01/21 23:24:27]

VideoSenderConfig::max_number_of_video_buffers_used means something completely
different from how you're using it here.

However, it's a codec-specific property.  I think it would be reasonable if you
just document (in cast_config.h) how the H264 codec interprets this value.

+  }
 }
 
 void H264VideoToolboxEncoder::Teardown() {
@@ -404,6 +434,21 @@ H264VideoToolboxEncoder::CreateVideoFrameFactory() {
       new VideoFrameFactoryCVPixelBufferPoolImpl(pool));
 }
 
+void H264VideoToolboxEncoder::EmitFrames() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  if (!compression_session_) {
+    DLOG(ERROR) << " compression session is null";
+    return;
+  }
+
+  OSStatus status = videotoolbox_glue_->VTCompressionSessionCompleteFrames(
+      compression_session_, CoreMediaGlue::CMTime{0, 0, 0, 0});
+  if (status != noErr) {
+    DLOG(ERROR) << " VTCompressionSessionCompleteFrames failed: " << status;
+  }
+}
+
 bool H264VideoToolboxEncoder::SetSessionProperty(CFStringRef key,
                                                  int32_t value) {
   base::ScopedCFTypeRef<CFNumberRef> cfvalue(