Linux Video Capture: Add V4L2VideoCaptureDelegate{Single,Multi}Plane.

media/video/capture/linux/v4l2_video_capture_delegate.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 MEDIA_VIDEO_CAPTURE_LINUX_V4L2_VIDEO_CAPTURE_DELEGATE_H_
+#define MEDIA_VIDEO_CAPTURE_LINUX_V4L2_VIDEO_CAPTURE_DELEGATE_H_
+
+#if defined(OS_OPENBSD)
+#include <sys/videoio.h>
+#else
+#include <linux/videodev2.h>
+#endif
+
+#include "base/files/scoped_file.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_vector.h"
+#include "media/video/capture/video_capture_device.h"
+
+namespace media {
+
+// Class doing the actual Linux capture using V4L2 API. V4L2 SPLANE/MPLANE
+// capture specifics are implemented in derived classes. Created and destroyed
+// on the owner's thread, otherwise living and operating on |v4l2_task_runner_|.
+class V4L2VideoCaptureDelegate
+    : public base::RefCountedThreadSafe<V4L2VideoCaptureDelegate> {
+ public:
+  // Creates the appropiate VideoCaptureDelegate according to parameters.
+  static scoped_refptr<V4L2VideoCaptureDelegate> CreateV4L2VideoCaptureDelegate(
+      const VideoCaptureDevice::Name& device_name,
+      const scoped_refptr<base::SingleThreadTaskRunner>& v4l2_task_runner,
+      int power_line_frequency);
+
+  // Retrieves the #planes for a given |fourcc|, or 0 if unknown.
+  static size_t GetNumPlanesForFourCc(uint32_t fourcc);
+  // Returns the Chrome pixel format for |v4l2_fourcc| or PIXEL_FORMAT_UNKNOWN.
+  static VideoPixelFormat V4l2FourCcToChromiumPixelFormat(uint32_t v4l2_fourcc);
+
+  // Composes a list of usable and supported pixel formats, in order of
+  // preference, with MJPEG prioritised depending on |prefer_mjpeg|.
+  static std::list<uint32_t> GetListOfUsableFourCcs(bool prefer_mjpeg);
+
+  // Forward-to versions of VideoCaptureDevice virtual methods.
+  void AllocateAndStart(int width,
+                        int height,
+                        float frame_rate,
+                        scoped_ptr<VideoCaptureDevice::Client> client);
+  void StopAndDeAllocate();
+
+  void SetRotation(int rotation);
+
+ protected:
+  // Class keeping track of SPLANE/MPLANE V4L2 buffers, mmap()ed on construction
+  // and munmap()ed on destruction. Destruction is syntactically equal for
+  // S/MPLANE but not construction, so this is implemented in derived classes.
+  // Internally it has a vector of planes, which for SPLANE will contain only
+  // one element.
+  class BufferTracker : public base::RefCounted<BufferTracker> {
+   public:
+    BufferTracker();
+    // Abstract method to mmap() given |fd| according to |buffer|, planarity
+    // specific.
+    virtual bool Init(int fd, const v4l2_buffer& buffer) = 0;
+
+    uint8_t* const GetPlaneStart(size_t plane) const {
+      return static_cast<uint8_t* const>(planes_[plane].start);

[perkj_chrome, 2015/03/19 20:38:17]

why is start a void ptr if you want a uint ptr?

[mcasas, 2015/03/19 22:57:01]

mmap() returns a void*.

I think it's easier to do the static_cast<uint8_t*>()
on Plane construction, changed.

+    }
+    size_t GetPlaneLength(size_t plane) const { return planes_[plane].length; }
+
+   protected:
+    friend class base::RefCounted<BufferTracker>;
+    virtual ~BufferTracker();
+    // Adds a given mmap()ed plane to |planes_|.
+    void AddMmapedPlane(void* const start, size_t length);
+
+   private:
+    struct Plane {
+      void* start;
+      size_t length;
+    };
+    std::vector<Plane> planes_;
+  };
+
+  V4L2VideoCaptureDelegate(
+      const VideoCaptureDevice::Name& device_name,
+      const scoped_refptr<base::SingleThreadTaskRunner>& v4l2_task_runner,
+      int power_line_frequency);
+  virtual ~V4L2VideoCaptureDelegate();
+
+  // Creates the necessary, planarity-specific, internal tracking schemes,
+  virtual scoped_refptr<BufferTracker> CreateBufferTracker() = 0;
+
+  // Fill in |format| with the given parameters, in a planarity dependent way.
+  virtual bool FillV4L2Format(v4l2_format* format,
+                              uint32_t width,
+                              uint32_t height,
+                              uint32_t pixelformat_fourcc) = 0;
+
+  // Finish filling |buffer| struct with planarity-dependent data.
+  virtual void FinishFillingV4L2Buffer(v4l2_buffer* buffer) const = 0;
+
+  // Sends the captured |buffer| to the |client_|, synchronously.
+  virtual void SendBuffer(
+      const scoped_refptr<BufferTracker>& buffer_tracker) = 0;
+
+  // A few accessors for SendBuffer()'s to access private member variables.
+  VideoCaptureFormat capture_format() const { return capture_format_; }
+  VideoCaptureDevice::Client* client() const { return client_.get(); }
+  int rotation() const { return rotation_; }
+
+ private:
+  friend class base::RefCountedThreadSafe<V4L2VideoCaptureDelegate>;
+
+  // Returns the input |fourcc| as a std::string four char representation.
+  static std::string FourccToString(uint32_t fourcc);
+  // VIDIOC_QUERYBUFs a buffer from V4L2, creates a BufferTracker for it and
+  // enqueues it (VIDIOC_QBUF) back into V4L2.
+  bool MapAndQueueBuffer(int index);
+  // Fills all common parts of |buffer|. Delegates to FinishFillingV4L2Buffer()
+  // for filling in the planar-dependent parts.
+  void FillV4L2Buffer(v4l2_buffer* buffer, int i) const;
+  void DoCapture();
+  void SetErrorState(const std::string& reason);
+
+  const v4l2_buf_type capture_type_;
+  const scoped_refptr<base::SingleThreadTaskRunner> v4l2_task_runner_;
+  const VideoCaptureDevice::Name device_name_;
+  const int power_line_frequency_;
+
+  // The following members are only known on AllocateAndStart().
+  VideoCaptureFormat capture_format_;
+  scoped_ptr<VideoCaptureDevice::Client> client_;
+  base::ScopedFD device_fd_;
+
+  // Vector of BufferTracker to keep track of mmap()ed pointers and their use.
+  std::vector<scoped_refptr<BufferTracker>> buffer_tracker_pool_;
+
+  bool is_capturing_;
+  int timeout_count_;
+
+  // Clockwise rotation in degrees. This value should be 0, 90, 180, or 270.
+  int rotation_;
+
+  DISALLOW_COPY_AND_ASSIGN(V4L2VideoCaptureDelegate);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_VIDEO_CAPTURE_LINUX_V4L2_VIDEO_CAPTURE_DELEGATE_H_