Video modesetting for v4l2

qtox.pro

@@ -459,7 +459,8 @@ SOURCES += \
     src/video/cameradevice.cpp \
     src/video/camerasource.cpp \
     src/video/corevideosource.cpp \
-    src/core/toxid.cpp
+    src/core/toxid.cpp \
+    src/platform/camera/v4l2.cpp
 
 
 HEADERS += \
@@ -493,4 +494,5 @@ HEADERS += \
     src/video/camerasource.h \
     src/video/corevideosource.h \
     src/video/videomode.h \
-    src/core/toxid.h
+    src/core/toxid.h \
+    src/platform/camera/v4l2.h

src/platform/camera/v4l2.cpp

@@ -0,0 +1,109 @@
+#include "v4l2.h"
+
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <linux/videodev2.h>
+
+/**
+ * Most of this file is adapted from libavdevice's v4l2.c,
+ * which retrieves useful information but only exposes it to
+ * stdout and is not part of the public API for some reason.
+ */
+
+static int deviceOpen(QString devName)
+{
+    struct v4l2_capability cap;
+    int fd;
+    int err;
+
+    fd = open(devName.toStdString().c_str(), O_RDWR, 0);
+    if (fd < 0)
+        return errno;
+
+    if (ioctl(fd, VIDIOC_QUERYCAP, &cap) < 0) {
+        err = errno;
+        goto fail;
+    }
+
+    if (!(cap.capabilities & V4L2_CAP_VIDEO_CAPTURE)) {
+        err = ENODEV;
+        goto fail;
+    }
+
+    if (!(cap.capabilities & V4L2_CAP_STREAMING)) {
+        err = ENOSYS;
+        goto fail;
+    }
+
+    return fd;
+
+fail:
+    close(fd);
+    return err;
+}
+
+static QVector<unsigned short> getDeviceModeFramerates(int fd, unsigned w, unsigned h, uint32_t pixelFormat)
+{
+    QVector<unsigned short> rates;
+    v4l2_frmivalenum vfve = { .pixel_format = pixelFormat, .height = h, .width = w };
+
+    while(!ioctl(fd, VIDIOC_ENUM_FRAMEINTERVALS, &vfve)) {
+        int rate;
+        switch (vfve.type) {
+        case V4L2_FRMSIZE_TYPE_DISCRETE:
+            rate = vfve.discrete.denominator / vfve.discrete.numerator;
+            if (!rates.contains(rate))
+                rates.append(rate);
+        break;
+        case V4L2_FRMSIZE_TYPE_CONTINUOUS:
+        case V4L2_FRMSIZE_TYPE_STEPWISE:
+            rate = vfve.stepwise.min.denominator / vfve.stepwise.min.numerator;
+            if (!rates.contains(rate))
+                rates.append(rate);
+        }
+        vfve.index++;
+    }
+
+    return rates;
+}
+
+QVector<VideoMode> v4l2::getDeviceModes(QString devName)
+{
+    QVector<VideoMode> modes;
+
+    int fd = deviceOpen(devName);
+    if (fd < 0)
+        return modes;
+    v4l2_fmtdesc vfd = { .type = V4L2_BUF_TYPE_VIDEO_CAPTURE };
+
+    while(!ioctl(fd, VIDIOC_ENUM_FMT, &vfd)) {
+        vfd.index++;
+
+        v4l2_frmsizeenum vfse = { .pixel_format = vfd.pixelformat };
+
+        while(!ioctl(fd, VIDIOC_ENUM_FRAMESIZES, &vfse)) {
+            VideoMode mode;
+            switch (vfse.type) {
+            case V4L2_FRMSIZE_TYPE_DISCRETE:
+                mode.width = vfse.discrete.width;
+                mode.height = vfse.discrete.height;
+            break;
+            case V4L2_FRMSIZE_TYPE_CONTINUOUS:
+            case V4L2_FRMSIZE_TYPE_STEPWISE:
+                mode.width = vfse.stepwise.max_width;
+                mode.height = vfse.stepwise.max_height;
+            }
+            QVector<unsigned short> rates = getDeviceModeFramerates(fd, mode.width, mode.height, vfd.pixelformat);
+            for (unsigned short rate : rates)
+            {
+                mode.FPS = rate;
+                if (!modes.contains(mode))
+                    modes.append(std::move(mode));
+            }
+            vfse.index++;
+        }
+    }
+
+    return modes;
+}

src/platform/camera/v4l2.h

@@ -0,0 +1,19 @@
+#ifndef V4L2_H
+#define V4L2_H
+
+#include <QString>
+#include <QVector>
+#include <QPair>
+#include "src/video/videomode.h"
+
+#ifndef Q_OS_LINUX
+#error "This file is only meant to be compiled for Linux targets"
+#endif
+
+namespace v4l2
+{
+    QVector<VideoMode> getDeviceModes(QString devName);
+}
+
+#endif // V4L2_H
+

src/video/cameradevice.cpp

@@ -9,6 +9,9 @@ extern "C" {
 #ifdef Q_OS_WIN
 #include "src/platform/camera/directshow.h"
 #endif
+#ifdef Q_OS_LINUX
+#include "src/platform/camera/v4l2.h"
+#endif
 
 QHash<QString, CameraDevice*> CameraDevice::openDevices;
 QMutex CameraDevice::openDeviceLock, CameraDevice::iformatLock;
@@ -62,6 +65,13 @@ CameraDevice* CameraDevice::open(QString devName, VideoMode mode)
         av_dict_set(&options, "video_size", QString("%1x%2").arg(mode.width).arg(mode.height).toStdString().c_str(), 0);
         av_dict_set(&options, "framerate", QString().setNum(mode.FPS).toStdString().c_str(), 0);
     }
+#endif
+#ifdef Q_OS_LINUX
+    else if (iformat->name == QString("video4linux2,v4l2"))
+    {
+        av_dict_set(&options, "video_size", QString("%1x%2").arg(mode.width).arg(mode.height).toStdString().c_str(), 0);
+        av_dict_set(&options, "framerate", QString().setNum(mode.FPS).toStdString().c_str(), 0);
+    }
 #endif
     else
     {
@@ -196,6 +206,10 @@ QVector<VideoMode> CameraDevice::getVideoModes(QString devName)
 #ifdef Q_OS_WIN
     else if (iformat->name == QString("dshow"))
         return DirectShow::getDeviceModes(devName);
+#endif
+#ifdef Q_OS_LINUX
+    else if (iformat->name == QString("video4linux2,v4l2"))
+        return v4l2::getDeviceModes(devName);
 #endif
     else
         qWarning() << "Video mode listing not implemented for input "<<iformat->name;

src/video/videomode.h

@@ -4,8 +4,8 @@
 /// Describes a video mode supported by a device
 struct VideoMode
 {
-    short width, height; ///< Displayed video resolution (NOT frame resolution)
+    unsigned short width, height; ///< Displayed video resolution (NOT frame resolution)
-    short FPS; ///< Max frames per second supported by the device at this resolution
+    unsigned short FPS; ///< Max frames per second supported by the device at this resolution
 
     /// All zeros means a default/unspecified mode
     operator bool()