MJPEG acceleration for video capture, browser part

content/browser/renderer_host/media/video_capture_device_client.cc

Index: content/browser/renderer_host/media/video_capture_device_client.cc
diff --git a/content/browser/renderer_host/media/video_capture_device_client.cc b/content/browser/renderer_host/media/video_capture_device_client.cc
index 33030ab6b621b4a418a618ef61273d08ef8e90e8..40bd94df737867d85bad5e890fc51d6ed8778b49 100644
--- a/content/browser/renderer_host/media/video_capture_device_client.cc
+++ b/content/browser/renderer_host/media/video_capture_device_client.cc
@@ -11,6 +11,7 @@
 #include "content/browser/gpu/browser_gpu_channel_host_factory.h"
 #include "content/browser/gpu/browser_gpu_memory_buffer_manager.h"
 #include "content/browser/gpu/gpu_data_manager_impl.h"
+#include "content/browser/renderer_host/gpu_jpeg_decoder.h"
 #include "content/browser/renderer_host/media/video_capture_buffer_pool.h"
 #include "content/browser/renderer_host/media/video_capture_controller.h"
 #include "content/common/gpu/client/context_provider_command_buffer.h"
@@ -200,13 +201,17 @@ VideoCaptureDeviceClient::VideoCaptureDeviceClient(
     const scoped_refptr<VideoCaptureBufferPool>& buffer_pool,
     const scoped_refptr<base::SingleThreadTaskRunner>& capture_task_runner)
     : controller_(controller),
+      external_jpeg_decoder_initialized_(false),
       buffer_pool_(buffer_pool),
       capture_task_runner_(capture_task_runner),
       last_captured_pixel_format_(media::PIXEL_FORMAT_UNKNOWN) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
 }
 
-VideoCaptureDeviceClient::~VideoCaptureDeviceClient() {}
+VideoCaptureDeviceClient::~VideoCaptureDeviceClient() {
+  DCHECK(capture_task_runner_->BelongsToCurrentThread());
+  external_jpeg_decoder_.reset();
+}
 
 void VideoCaptureDeviceClient::OnIncomingCapturedData(
     const uint8* data,
@@ -220,6 +225,23 @@ void VideoCaptureDeviceClient::OnIncomingCapturedData(
     OnLog("Pixel format: " + media::VideoCaptureFormat::PixelFormatToString(
                                  frame_format.pixel_format));
     last_captured_pixel_format_ = frame_format.pixel_format;
+
+    if (frame_format.pixel_format == media::PIXEL_FORMAT_MJPEG &&
+        !external_jpeg_decoder_initialized_) {
+      external_jpeg_decoder_initialized_ = true;
+      if (GpuJpegDecoder::Supported()) {
+        // base::Unretained is safe because |this| outlives
+        // |external_jpeg_decoder_|.
+        external_jpeg_decoder_.reset(new GpuJpegDecoder(
+            base::Bind(
+                &VideoCaptureController::DoIncomingCapturedVideoFrameOnIOThread,
+                controller_),
+            // TODO(kcwu): fallback to software decode if error.
+            base::Bind(&VideoCaptureDeviceClient::OnError,
+                       base::Unretained(this))));

[piman, 2015/06/20 00:33:57]

nit: can you add a comment about why Unretained is safe?

[kcwu, 2015/06/20 00:47:08]

line 233 does. Do you want me to explain it further?

[piman, 2015/06/20 00:59:26]

Oh, missed that. I guess that's fine... the main thing is that callbacks happen
on the IO thread, so it's not necessarily obvious why they don't happen even
after the external_jpeg_decoder_ is destroyed (there's an explicit wait in the
GpuJpegDecodeAcceleratorHost). Maybe worth mentioning in the GpuJpegDecoder
class? The callbacks are called on the IO thread but never after the
GpuJpegDecoder is destroyed?

[kcwu, 2015/06/20 01:26:10]

Done.

+        external_jpeg_decoder_->Initialize();
+      }
+    }
   }
 
   if (!frame_format.IsValid())
@@ -333,6 +355,14 @@ void VideoCaptureDeviceClient::OnIncomingCapturedData(
   // paddings and/or alignments, but it cannot be smaller.
   DCHECK_GE(static_cast<size_t>(length), frame_format.ImageAllocationSize());
 
+  if (external_jpeg_decoder_ &&
+      frame_format.pixel_format == media::PIXEL_FORMAT_MJPEG && rotation == 0 &&
+      !flip && external_jpeg_decoder_->ReadyToDecode()) {
+    external_jpeg_decoder_->DecodeCapturedData(data, length, frame_format,
+                                               timestamp, buffer.Pass());
+    return;
+  }
+
   if (libyuv::ConvertToI420(data,
                             length,
                             yplane,