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      1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 // Linux specific implementation of VideoCaptureDevice.
      6 // V4L2 is used for capturing. V4L2 does not provide its own thread for
      7 // capturing so this implementation uses a Chromium thread for fetching frames
      8 // from V4L2.
      9 
     10 #ifndef MEDIA_VIDEO_CAPTURE_LINUX_VIDEO_CAPTURE_DEVICE_LINUX_H_
     11 #define MEDIA_VIDEO_CAPTURE_LINUX_VIDEO_CAPTURE_DEVICE_LINUX_H_
     12 
     13 #include <string>
     14 
     15 #include "base/threading/thread.h"
     16 #include "media/video/capture/video_capture_device.h"
     17 #include "media/video/capture/video_capture_types.h"
     18 
     19 namespace media {
     20 
     21 class VideoCaptureDeviceLinux : public VideoCaptureDevice {
     22  public:
     23   explicit VideoCaptureDeviceLinux(const Name& device_name);
     24   virtual ~VideoCaptureDeviceLinux();
     25 
     26   // VideoCaptureDevice implementation.
     27   virtual void Allocate(const VideoCaptureCapability& capture_format,
     28                          EventHandler* observer) OVERRIDE;
     29   virtual void Start() OVERRIDE;
     30   virtual void Stop() OVERRIDE;
     31   virtual void DeAllocate() OVERRIDE;
     32   virtual const Name& device_name() OVERRIDE;
     33 
     34  private:
     35   enum InternalState {
     36     kIdle,  // The device driver is opened but camera is not in use.
     37     kAllocated,  // The camera has been allocated and can be started.
     38     kCapturing,  // Video is being captured.
     39     kError  // Error accessing HW functions.
     40             // User needs to recover by destroying the object.
     41   };
     42 
     43   // Buffers used to receive video frames from with v4l2.
     44   struct Buffer {
     45     Buffer() : start(0), length(0) {}
     46     void* start;
     47     size_t length;
     48   };
     49 
     50   // Called on the v4l2_thread_.
     51   void OnAllocate(int width,
     52                   int height,
     53                   int frame_rate,
     54                   EventHandler* observer);
     55   void OnStart();
     56   void OnStop();
     57   void OnDeAllocate();
     58   void OnCaptureTask();
     59 
     60   bool AllocateVideoBuffers();
     61   void DeAllocateVideoBuffers();
     62   void SetErrorState(const std::string& reason);
     63 
     64   InternalState state_;
     65   VideoCaptureDevice::EventHandler* observer_;
     66   Name device_name_;
     67   int device_fd_;  // File descriptor for the opened camera device.
     68   base::Thread v4l2_thread_;  // Thread used for reading data from the device.
     69   Buffer* buffer_pool_;
     70   int buffer_pool_size_;  // Number of allocated buffers.
     71   int timeout_count_;
     72 
     73   DISALLOW_IMPLICIT_CONSTRUCTORS(VideoCaptureDeviceLinux);
     74 };
     75 
     76 }  // namespace media
     77 
     78 #endif  // MEDIA_VIDEO_CAPTURE_LINUX_VIDEO_CAPTURE_DEVICE_LINUX_H_
     79