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// Copyright (c) 2011 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.
//
// VideoCaptureDevice is the abstract base class for realizing video capture
// device support in Chromium. It provides the interface for OS dependent
// implementations.
// The class is created and functions are invoked on a thread owned by
// VideoCaptureManager. Capturing is done on other threads depended on the OS
// specific implementation.
#ifndef MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
#define MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
#include <list>
#include <string>
#include "base/time.h"
#include "media/base/media_export.h"
namespace media {
class MEDIA_EXPORT VideoCaptureDevice {
public:
struct Name {
// Friendly name of a device
std::string device_name;
// Unique name of a device. Even if there are multiple devices with the same
// friendly name connected to the computer this will be unique.
std::string unique_id;
};
typedef std::list<Name> Names;
// Color formats from camera.
enum Format {
kColorUnknown, // Color format not set.
kI420,
kYUY2,
kUYVY,
kRGB24,
kARGB,
kMJPEG, // Currently only supported on Windows.
};
// Describes the format a camera capture video in.
struct Capability {
Capability()
: width(0),
height(0),
frame_rate(0),
color(kColorUnknown) {}
int width;
int height;
int frame_rate;
Format color;
};
class EventHandler {
public:
// Captured a new video frame.
virtual void OnIncomingCapturedFrame(const uint8* data,
int length,
base::Time timestamp) = 0;
// An error has occurred that can not be handled
// and VideoCaptureDevice must be DeAllocated.
virtual void OnError() = 0;
// Called when VideoCaptureDevice::Allocate has been called
// to inform of the resulting frame size and color format.
virtual void OnFrameInfo(const Capability& info) = 0;
protected:
virtual ~EventHandler() {}
};
// Creates a VideoCaptureDevice object.
// Return NULL if the hardware is not available.
static VideoCaptureDevice* Create(const Name& device_name);
virtual ~VideoCaptureDevice() {}
// Gets the names of all video capture devices connected to this computer.
static void GetDeviceNames(Names* device_names);
// Prepare the camera for use. After this function has been called no other
// applications can use the camera. On completion EventHandler::OnFrameInfo is
// called informing of the resulting resolution and frame rate.
// DeAllocate must be called before this function can be called again and
// before the object is deleted.
virtual void Allocate(int width,
int height,
int frame_rate,
EventHandler* observer) = 0;
// Start capturing video frames. Allocate must be called before this function.
virtual void Start() = 0;
// Stop capturing video frames.
virtual void Stop() = 0;
// DeAllocates the camera. This means other applications can use it.
// After this function has been called the Capture device is reset to the
// state it was when created.
virtual void DeAllocate() = 0;
// Get the name of the capture device.
virtual const Name& device_name() = 0;
};
} // namespace media
#endif // MEDIA_VIDEO_CAPTURE_VIDEO_CAPTURE_DEVICE_H_
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