qTox/src/video/cameradevice.h

/*
    Copyright © 2015 by The qTox Project

    This file is part of qTox, a Qt-based graphical interface for Tox.

    qTox is libre software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    qTox is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with qTox.  If not, see <http://www.gnu.org/licenses/>.
*/


#ifndef CAMERADEVICE_H
#define CAMERADEVICE_H

#include <QHash>
#include <QString>
#include <QMutex>
#include <QVector>
#include <atomic>
#include "videomode.h"

struct AVFormatContext;
struct AVInputFormat;
struct AVDeviceInfoList;
struct AVDictionary;

/// Maintains an FFmpeg context for open camera devices,
/// takes care of sharing the context accross users
/// and closing the camera device when not in use.
/// The device can be opened recursively,
/// and must then be closed recursively
class CameraDevice
{
public:
    /// Opens a device, creating a new one if needed
    /// If the device is alreay open in another mode, the mode
    /// will be ignored and the existing device is used
    /// If the mode does not exist, a new device can't be opened
    /// Returns a nullptr if the device couldn't be opened
    static CameraDevice* open(QString devName, VideoMode mode = VideoMode());
    void open(); ///< Opens the device again. Never fails
    bool close(); ///< Closes the device. Never fails. If returns true, "this" becomes invalid

    /// Returns a list of device names and descriptions
    /// The names are the first part of the pair and can be passed to open(QString)
    static QVector<QPair<QString, QString>> getDeviceList();

    /// Get the list of video modes for a device
    static QVector<VideoMode> getVideoModes(QString devName);
    /// Get the name of the pixel format of a video mode
    static QString getPixelFormatString(uint32_t pixel_format);
    /// Returns true if we prefer format a to b, false otherwise (such as if there's no preference)
    static bool betterPixelFormat(uint32_t a, uint32_t b);

    /// Returns the short name of the default defice
    /// This is either the device in the settings
    /// or the system default.
    static QString getDefaultDeviceName();

    /// Checks if a device name specifies a display
    static bool isScreen(const QString &devName);

private:
    CameraDevice(const QString &devName, AVFormatContext *context);
    static CameraDevice* open(QString devName, AVDictionary** options);
    static bool getDefaultInputFormat(); ///< Sets CameraDevice::iformat, returns success/failure
    static QVector<QPair<QString, QString> > getRawDeviceListGeneric(); ///< Uses avdevice_list_devices
    static QVector<VideoMode> getScreenModes(); ///< Returns avaliable screen modes with offset

public:
    const QString devName; ///< Short name of the device
    AVFormatContext* context; ///< Context of the open device, must always be valid

private:
    std::atomic_int refcount; ///< Number of times the device was opened
    static QHash<QString, CameraDevice*> openDevices;
    static QMutex openDeviceLock, iformatLock;
    static AVInputFormat* iformat, *idesktopFormat;
};

#endif // CAMERADEVICE_H