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