MJPEG acceleration for V4L2

content/common/gpu/media/v4l2_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_V4L2_JPEG_DECODE_ACCELERATOR_H_
+#define CONTENT_COMMON_GPU_MEDIA_V4L2_JPEG_DECODE_ACCELERATOR_H_
+
+#include <queue>
+#include <vector>
+
+#include "base/memory/linked_ptr.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
+#include "base/single_thread_task_runner.h"
+#include "base/threading/thread.h"
+#include "content/common/content_export.h"
+#include "content/common/gpu/media/v4l2_device.h"
+#include "media/base/bitstream_buffer.h"
+#include "media/base/video_frame.h"
+#include "media/video/jpeg_decode_accelerator.h"
+
+namespace content {
+
+class CONTENT_EXPORT V4L2JpegDecodeAccelerator
+    : public media::JpegDecodeAccelerator {
+ public:
+  V4L2JpegDecodeAccelerator(
+      const scoped_refptr<V4L2Device>& device,
+      const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);
+  ~V4L2JpegDecodeAccelerator() override;
+
+  // media::JpegDecodeAccelerator implementation.
+  bool Initialize(Client* client) override;
+  void Decode(const media::BitstreamBuffer& bitstream_buffer,
+              const scoped_refptr<media::VideoFrame>& video_frame) override;
+
+ private:
+  // Record for input/output buffers.
+  struct BufferRecord {
+    BufferRecord();
+    ~BufferRecord();
+    void* address;          // mmap() address.
+    size_t length;          // mmap() length.
+
+    // Set true during QBUF and DQBUF. |adress| will be accessed by hardware.

[wuchengli, 2015/06/22 22:40:55]

s/adress/address/

[henryhsu, 2015/06/23 10:08:17]

Done.

+    bool at_device;
+  };
+
+  // Job record. Jobs are processed in a FIFO order. This is separate from
+  // BufferRecord of input, because a BufferRecord of input may be returned
+  // before we dequeue the corresponding output buffer. It can't always be
+  // associated with a BufferRecord of output immediately either, because at
+  // the time of submission we may not have one available (and don't need one
+  // to submit input to the device).
+  struct JobRecord {
+    JobRecord(media::BitstreamBuffer bitstream_buffer,
+              scoped_refptr<media::VideoFrame> video_frame);
+    ~JobRecord();
+    media::BitstreamBuffer bitstream_buffer;

[wuchengli, 2015/06/22 22:40:55]

Document these three variables. Also mention |bitstream_buffer| is input and
|frame| is output.

[henryhsu, 2015/06/23 10:08:17]

Done.

+    scoped_refptr<media::VideoFrame> frame;

[wuchengli, 2015/06/22 22:40:55]

s/frame/output_frame/ so it's more obvious what this is.

[henryhsu, 2015/06/23 10:08:17]

Done.

+    scoped_ptr<base::SharedMemory> shm;

[wuchengli, 2015/06/22 22:40:54]

Document this is mapped from |bitstream_buffer|.

[henryhsu, 2015/06/23 10:08:17]

Done.

+  };
+
+  void Enqueue();
+  void Dequeue();
+  bool EnqueueInputRecord();
+  bool EnqueueOutputRecord();
+  bool CreateInputBuffers();
+  bool CreateOutputBuffers();
+  void DestroyInputBuffers();
+  void DestroyOutputBuffers();
+  // Check resolution and input buffer size to decide recreate buffers.
+  void CheckBufferAttributes();
+  // Create input and output buffer if needed.
+  bool CreateBufferIfNecessary();

[wuchengli, 2015/06/22 22:40:55]

Document the return value -- False means an error has occurred. Otherwise,
people will think true means buffers have been created. 

[henryhsu, 2015/06/23 10:08:17]

Done.

+
+  void NotifyError(int32_t bitstream_buffer_id, Error error);
+  void PostNotifyError(int32_t bitstream_buffer_id, Error error);
+
+  // Run on |decoder_thread_| to enqueue the coming frame.
+  void DecodeTask(scoped_ptr<JobRecord> job_record);
+
+  // Run on |decoder_thread_| to dequeue last frame and enqueue next frame.
+  // This task is triggered by DevicePollTask.
+  void ServiceDeviceTask();
+
+  // Start/Stop |device_poll_thread_|.
+  void StartDevicePoll();
+  bool StopDevicePoll();
+
+  // Run on |device_poll_thread_| to wait for device events.
+  void DevicePollTask();
+
+  // Run on |decoder_thread_| to destroy input and output buffers.
+  void DestroyTask();
+
+  const size_t kBufferCount = 2;

[wuchengli, 2015/06/22 22:40:55]

Document this is the number of input buffers and output buffers.

[henryhsu, 2015/06/23 10:08:17]

Done.

+
+  // Current image size used for checking the size is changed.
+  gfx::Size image_coded_size_;
+
+  // Set true when input or output buffers have to re-allocate.

[wuchengli, 2015/06/22 22:40:55]

s/re-allocate/be re-allocated/

[henryhsu, 2015/06/23 10:08:17]

Done.

+  bool recreate_input_buffers_pending_;
+  bool recreate_output_buffers_pending_;
+
+  // ChildThread's task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> child_task_runner_;
+
+  // GPU IO task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> io_task_runner_;
+
+  // The client of this class.
+  Client* client_;
+
+  // The V4L2Device this class is operating upon.
+  scoped_refptr<V4L2Device> device_;
+
+  // Thread to communicate with the device.
+  base::Thread decoder_thread_;
+  // Decode task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> decoder_task_runner_;
+  // Thread used to poll the V4L2 for events only.
+  base::Thread device_poll_thread_;
+  // Device poll task runner.
+  scoped_refptr<base::SingleThreadTaskRunner> device_poll_task_runner_;
+
+  // All the below members are accessed from |decoder_thread_| only

[wuchengli, 2015/06/22 22:40:55]

All the below members except |weak_factory_|

[henryhsu, 2015/06/23 10:08:17]

Done.

+  // (if it's running).
+  std::queue<linked_ptr<JobRecord> > input_jobs_;
+  std::queue<linked_ptr<JobRecord> > running_jobs_;
+
+  // Input queue state.
+  bool input_streamon_;
+  // Number of input buffers enqueued to the device.
+  int input_buffer_queued_count_;
+  // Mapping of int index to an input buffer record.
+  std::vector<BufferRecord> input_buffer_map_;
+  // Indices of input buffers ready to use; LIFO since we don't care about
+  // ordering.
+  std::vector<int> free_input_buffers_;
+
+  // Output queue state.
+  bool output_streamon_;
+  // Number of output buffers enqueued to the device.
+  int output_buffer_queued_count_;
+  // Mapping of int index to an output buffer record.
+  std::vector<BufferRecord> output_buffer_map_;
+  // Indices of output buffers ready to use; LIFO since we don't care about
+  // ordering.
+  std::vector<int> free_output_buffers_;
+
+  // Weak factory for producing weak pointers on the decoder_thread_

[wuchengli, 2015/06/22 22:40:55]

s/decoder/child/

[henryhsu, 2015/06/23 10:08:17]

Done.

+  base::WeakPtrFactory<V4L2JpegDecodeAccelerator> weak_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(V4L2JpegDecodeAccelerator);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_GPU_MEDIA_V4L2_JPEG_DECODE_ACCELERATOR_H_