MJPEG acceleration for video capture using VAAPI, the GPU and IPC part

content/common/gpu/media/vaapi_jpeg_decode_accelerator.h

+// Copyright 2015 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_VAAPI_JPEG_DECODE_ACCELERATOR_H_
+#define CONTENT_COMMON_GPU_MEDIA_VAAPI_JPEG_DECODE_ACCELERATOR_H_
+
+#include <queue>
+
+#include "base/memory/linked_ptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/synchronization/lock.h"
+#include "base/threading/non_thread_safe.h"
+#include "base/threading/thread.h"
+#include "content/common/content_export.h"
+#include "content/common/gpu/media/vaapi_jpeg_decoder.h"
+#include "content/common/gpu/media/vaapi_wrapper.h"
+#include "media/base/bitstream_buffer.h"
+#include "media/video/jpeg_decode_accelerator.h"
+
+namespace content {
+
+// Class to provide JPEG decode acceleration for Intel systems with hardware
+// support for it, and on which libva is available.
+// Decoding tasks are performed in a separate decoding thread.
+//
+// Threading/life-cycle: this object is created & destroyed on the GPU
+// ChildThread.  A few methods on it are called on the decoder thread which is
+// stopped during |this->Destroy()|, so any tasks posted to the decoder thread
+// can assume |*this| is still alive.  See |weak_this_| below for more details.
+class CONTENT_EXPORT VaapiJpegDecodeAccelerator
+    : public media::JpegDecodeAccelerator {
+ public:
+  VaapiJpegDecodeAccelerator(
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  ~VaapiJpegDecodeAccelerator() override;
+
+  // media::JpegDecodeAccelerator implementation.
+  bool Initialize(media::JpegDecodeAccelerator::Client* client) override;
+  void Decode(const media::BitstreamBuffer& bitstream_buffer,
+              const scoped_refptr<media::VideoFrame>& video_frame) override;
+
+ private:
+  // Notifies the client that an error has occurred and decoding cannot
+  // continue.
+  void NotifyError(int32_t bitstream_buffer_id, Error error);
+  void NotifyErrorFromDecoderThread(int32_t bitstream_buffer_id, Error error);
+  void VideoFrameReady(int32_t bitstream_buffer_id);
+
+  // Processes one decode request in the queue.

[Pawel Osciak, 2015/05/28 09:13:18]

s/queue/decode_requests_ queue/

[kcwu, 2015/05/28 12:10:28]

Acknowledged.

+  void DecodeTask();
+
+  // Helper for destroy, doing all the actual work except for deleting self.

[Pawel Osciak, 2015/05/28 09:13:18]

Do we need this helper? It's only called once from destructor and we don't
delete self anymore.

[kcwu, 2015/05/28 12:10:28]

Done.

+  void Cleanup();
+
+  // Puts contents of |va_surface| into given |video_frame|, releases the
+  // surface and passes the buffer id of the resulting picture to client for

[Pawel Osciak, 2015/05/28 09:13:18]

s/buffer id/|input_buffer_id|/ ?

[kcwu, 2015/05/28 12:10:28]

Done.

+  // output.
+  bool OutputPicture(VASurfaceID va_surface_id,
+                     int32_t input_buffer_id,
+                     const scoped_refptr<media::VideoFrame>& video_frame);
+
+  // Protects |decode_requests_| and |initialized_|.

[Pawel Osciak, 2015/05/28 09:13:18]

Could we instead post a task to decoder thread to add to decode_requests_ on it
without locking?

[kcwu, 2015/05/28 12:10:28]

Done.

+  base::Lock lock_;
+  bool initialized_;

[Pawel Osciak, 2015/05/28 09:13:18]

Since we Stop() the decoder thread before setting initialized_ to false and set
it to true when starting the thread, could just having the decoder thread
running mean initialized_ == true, and the decoder thread would not have to
check this, since it'd have been stopped if initialized_ == false anyway?

[kcwu, 2015/05/28 12:10:28]

Done.

+
+  // An input buffer and the corresponding output video frame awaiting
+  // consumption, provided by the client.
+  struct DecodeRequest {
+    DecodeRequest(const media::BitstreamBuffer& bitstream_buffer,
+                  scoped_refptr<media::VideoFrame> video_frame);
+    ~DecodeRequest();
+
+    media::BitstreamBuffer bitstream_buffer;
+    scoped_refptr<media::VideoFrame> video_frame;
+  };
+
+  // Queue for incoming decode requests.
+  typedef std::queue<linked_ptr<DecodeRequest>> DecodeRequests;

[Pawel Osciak, 2015/05/28 09:13:18]

You may want to use the new c++11 style (if you like):
using DecodeRequests = std::queue<linked_ptr<DecodeRequest>>;

[kcwu, 2015/05/28 12:10:28]

Acknowledged.

+  DecodeRequests decode_requests_;
+
+  // ChildThread's task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
+  // GPU IO task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  // The client of this class.
+  Client* client_;

[Pawel Osciak, 2015/05/28 09:13:18]

Could we use a WeakPtr instead?

[kcwu, 2015/05/28 12:10:28]

It was. And we found it could be not a WeakPtr from the review.

+
+  // WeakPtr<> pointing to |this| for use in posting tasks from the decoder
+  // thread back to the ChildThread.  Because the decoder thread is a member of
+  // this class, any task running on the decoder thread is guaranteed that this
+  // object is still alive.  As a result, tasks posted from ChildThread to
+  // decoder thread should use base::Unretained(this), and tasks posted from the
+  // decoder thread to the ChildThread should use |weak_this_|.
+  base::WeakPtr<VaapiJpegDecodeAccelerator> weak_this_;
+
+  scoped_ptr<VaapiWrapper> vaapi_wrapper_;
+
+  // Comes after vaapi_wrapper_ to ensure its destructor is executed before
+  // |vaapi_wrapper_| is destroyed.
+  scoped_ptr<VaapiJpegDecoder> decoder_;
+  base::Thread decoder_thread_;
+  // Use this to post tasks to |decoder_thread_| instead of
+  // |decoder_thread_.task_runner()| because the latter will be NULL once
+  // |decoder_thread_.Stop()| returns.
+  scoped_refptr<base::SingleThreadTaskRunner> decoder_task_runner_;
+
+  // The current VA surface for decoding.
+  VASurfaceID va_surface_;

[Pawel Osciak, 2015/05/28 09:13:18]

s/va_surface_/va_surface_id_/

[kcwu, 2015/05/28 12:10:28]

Done.

+  // The coded size associated with |va_surface_|.
+  gfx::Size coded_size_;
+
+  // The WeakPtrFactory for |weak_this_|.
+  base::WeakPtrFactory<VaapiJpegDecodeAccelerator> weak_this_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(VaapiJpegDecodeAccelerator);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_MEDIA_VAAPI_JPEG_DECODE_ACCELERATOR_H_