Implement DirectShow video dev listing

We can now get the list of video devices with the dshow ffmpeg device
(so, on Windows). Most of this patch is adapted from libavdevice's dshow
private internal interface, which retrieves useful info but is only
designed to log it to stdout. We reimplement that to get an actual list
of devices names/descriptions, that we can then open with ffmpeg the
refular way.

qtox.pro

@@ -133,8 +133,9 @@ win32 {
     RC_FILE = windows/qtox.rc
 	LIBS += -L$$PWD/libs/lib -ltoxav -ltoxcore -ltoxencryptsave -ltoxdns -lsodium -lvpx -lpthread
 	LIBS += -L$$PWD/libs/lib -lavformat -lavdevice -lavcodec -lavutil -lswscale -lOpenAL32 -lopus
-    LIBS += -lopengl32 -lole32 -loleaut32 -luuid -lvfw32 -lws2_32 -liphlpapi -lz
+    LIBS += -lopengl32 -lole32 -loleaut32 -lvfw32 -lws2_32 -liphlpapi -lz -luuid
     LIBS += -lqrencode
+    LIBS += -lstrmiids # For DirectShow
     contains(DEFINES, QTOX_FILTER_AUDIO) {
         contains(STATICPKG, YES) {
             LIBS += -Wl,-Bstatic -lfilteraudio
@@ -359,7 +360,7 @@ contains(ENABLE_SYSTRAY_GTK_BACKEND, NO) {
         src/misc/qrwidget.h \
         src/widget/systemtrayicon_private.h
 
-        SOURCES += \
+    SOURCES += \
         src/widget/form/addfriendform.cpp \
         src/widget/form/settingswidget.cpp \
         src/widget/form/settings/generalform.cpp \
@@ -420,6 +421,14 @@ contains(ENABLE_SYSTRAY_GTK_BACKEND, NO) {
         src/widget/genericchatroomwidget.cpp
 }
 
+win32 {
+    HEADERS += \
+        src/platform/camera/directshow.h
+
+    SOURCES += \
+        src/platform/camera/directshow.cpp
+}
+
 SOURCES += \
     src/audio.cpp \
     src/historykeeper.cpp \

src/platform/camera/directshow.cpp

@@ -0,0 +1,85 @@
+#include "directshow.h"
+
+#include <cstdint>
+#include <Objbase.h>
+#include <Strmif.h>
+#include <uuids.h>
+
+/**
+ * Most of this file is adapted from libavdevice's dshow.c,
+ * which retrieves useful information but only exposes it to
+ * stdout and is not part of the public API for some reason.
+ */
+
+static char *wcharToUtf8(wchar_t *w)
+{
+    int l = WideCharToMultiByte(CP_UTF8, 0, w, -1, 0, 0, 0, 0);
+    char *s = new char[l];
+    if (s)
+        WideCharToMultiByte(CP_UTF8, 0, w, -1, s, l, 0, 0);
+    return s;
+}
+
+QVector<QPair<QString,QString>> DirectShow::getDeviceList()
+{
+    IMoniker* m = nullptr;
+    QVector<QPair<QString,QString>> devices;
+
+    ICreateDevEnum* devenum = nullptr;
+    if (CoCreateInstance(CLSID_SystemDeviceEnum, nullptr, CLSCTX_INPROC_SERVER,
+                             IID_ICreateDevEnum, (void**) &devenum) != S_OK)
+        return devices;
+
+    IEnumMoniker* classenum = nullptr;
+    if (devenum->CreateClassEnumerator(CLSID_VideoInputDeviceCategory,
+                                (IEnumMoniker**)&classenum, 0) != S_OK)
+        return devices;
+
+    while (classenum->Next(1, &m, nullptr) == S_OK)
+    {
+        VARIANT var;
+        IPropertyBag* bag = nullptr;
+        LPMALLOC coMalloc = nullptr;
+        IBindCtx* bindCtx = nullptr;
+        LPOLESTR olestr = nullptr;
+        char *devIdString=nullptr, *devHumanName=nullptr;
+
+        if (CoGetMalloc(1, &coMalloc) != S_OK)
+            goto fail;
+        if (CreateBindCtx(0, &bindCtx) != S_OK)
+            goto fail;
+        if (m->GetDisplayName(bindCtx, nullptr, &olestr) != S_OK)
+            goto fail;
+
+        devIdString = wcharToUtf8(olestr);
+
+        // replace ':' with '_' since FFmpeg uses : to delimitate sources
+        for (unsigned i = 0; i < strlen(devIdString); i++)
+            if (devIdString[i] == ':')
+                devIdString[i] = '_';
+
+        if (m->BindToStorage(nullptr, nullptr, IID_IPropertyBag, (void**)&bag) != S_OK)
+            goto fail;
+
+        var.vt = VT_BSTR;
+        if (bag->Read(L"FriendlyName", &var, nullptr) != S_OK)
+            goto fail;
+        devHumanName = wcharToUtf8(var.bstrVal);
+
+        devices += {QString("video=")+devIdString, devHumanName};
+
+fail:
+        if (olestr && coMalloc)
+            coMalloc->Free(olestr);
+        if (bindCtx)
+            bindCtx->Release();
+        delete[] devIdString;
+        delete[] devHumanName;
+        if (bag)
+            bag->Release();
+        m->Release();
+    }
+    classenum->Release();
+
+    return devices;
+}

src/platform/camera/directshow.h

@@ -0,0 +1,21 @@
+#ifndef DIRECTSHOW_H
+#define DIRECTSHOW_H
+
+#include <QString>
+#include <QVector>
+#include <QPair>
+
+#ifndef Q_OS_WIN
+#error "This file is only meant to be compiled for Windows targets"
+#endif
+
+class DirectShow
+{
+public:
+    static QVector<QPair<QString,QString>> getDeviceList();
+
+private:
+    DirectShow()=delete;
+};
+
+#endif // DIRECTSHOW_H

src/video/cameradevice.cpp

@@ -6,6 +6,10 @@ extern "C" {
 #include "cameradevice.h"
 #include "src/misc/settings.h"
 
+#ifdef Q_OS_WIN
+#include "src/platform/camera/directshow.h"
+#endif
+
 QHash<QString, CameraDevice*> CameraDevice::openDevices;
 QMutex CameraDevice::openDeviceLock, CameraDevice::iformatLock;
 AVInputFormat* CameraDevice::iformat{nullptr};
@@ -24,7 +28,7 @@ CameraDevice* CameraDevice::open(QString devName)
     if (dev)
         goto out;
 
-    if (avformat_open_input(&fctx, devName.toStdString().c_str(), nullptr, nullptr)<0)
+    if (avformat_open_input(&fctx, devName.toStdString().c_str(), iformat, nullptr)<0)
         goto out;
 
     if (avformat_find_stream_info(fctx, NULL) < 0)
@@ -63,21 +67,21 @@ bool CameraDevice::close()
     }
 }
 
-AVDeviceInfoList* CameraDevice::getRawDeviceList()
+QVector<QPair<QString, QString>> CameraDevice::getRawDeviceListGeneric()
 {
-    AVDeviceInfoList* devlist = nullptr;
+    QVector<QPair<QString, QString>> devices;
 
     if (!getDefaultInputFormat())
-        return devlist;
+        return devices;
 
     // Alloc an input device context
     AVFormatContext *s;
     if (!(s = avformat_alloc_context()))
-        return devlist;
+        return devices;
     if (!iformat->priv_class || !AV_IS_INPUT_DEVICE(iformat->priv_class->category))
     {
         avformat_free_context(s);
-        return devlist;
+        return devices;
     }
     s->iformat = iformat;
     if (s->iformat->priv_data_size > 0)
@@ -86,7 +90,7 @@ AVDeviceInfoList* CameraDevice::getRawDeviceList()
         if (!s->priv_data)
         {
             avformat_free_context(s);
-            return devlist;
+            return devices;
         }
         if (s->iformat->priv_class)
         {
@@ -100,6 +104,7 @@ AVDeviceInfoList* CameraDevice::getRawDeviceList()
     }
 
     // List the devices for this context
+    AVDeviceInfoList* devlist = nullptr;
     AVDictionary *tmp = nullptr;
     av_dict_copy(&tmp, nullptr, 0);
     if (av_opt_set_dict2(s, &tmp, AV_OPT_SEARCH_CHILDREN) < 0)
@@ -108,16 +113,8 @@ AVDeviceInfoList* CameraDevice::getRawDeviceList()
         avformat_free_context(s);
     }
     avdevice_list_devices(s, &devlist);
-    return devlist;
-}
-
-QVector<QPair<QString, QString>> CameraDevice::getDeviceList()
-{
-    QVector<QPair<QString, QString>> devices;
-
-    AVDeviceInfoList* devlist = getRawDeviceList();
     if (!devlist)
-        return devices;
+        qWarning() << "avdevice_list_devices failed";
 
     // Convert the list to a QVector
     devices.resize(devlist->nb_devices);
@@ -128,47 +125,37 @@ QVector<QPair<QString, QString>> CameraDevice::getDeviceList()
         devices[i].second = dev->device_description;
     }
     avdevice_free_list_devices(&devlist);
-
     return devices;
 }
 
+QVector<QPair<QString, QString>> CameraDevice::getDeviceList()
+{
+    if (!iformat)
+        if (!getDefaultInputFormat())
+            return {};
+
+    if (iformat->name == QString("dshow"))
+        return DirectShow::getDeviceList();
+    else
+        return getRawDeviceListGeneric();
+}
+
 QString CameraDevice::getDefaultDeviceName()
 {
-    QString device = Settings::getInstance().getVideoDev();
+    QString defaultdev = Settings::getInstance().getVideoDev();
 
     if (!getDefaultInputFormat())
-        return device;
+        return defaultdev;
 
-    AVDeviceInfoList* devlist = getRawDeviceList();
-    if (!devlist)
-        return device;
+    QVector<QPair<QString, QString>> devlist = getDeviceList();
+    for (const QPair<QString,QString>& device : devlist)
+        if (defaultdev == device.first)
+            return defaultdev;
 
-    bool actuallyExists = false;
-    for (int i=0; i<devlist->nb_devices; i++)
-    {
-        if (device == devlist->devices[i]->device_name)
-        {
-            actuallyExists = true;
-            break;
-        }
-    }
-    if (actuallyExists)
-    {
-        avdevice_free_list_devices(&devlist);
-        return device;
-    }
+    if (devlist.isEmpty())
+        return defaultdev;
 
-    if (!devlist->nb_devices)
-    {
-        device.clear();
-    }
-    else
-    {
-        int defaultDev = devlist->default_device == -1 ? 0 : devlist->default_device;
-        device = QString(devlist->devices[defaultDev]->device_name);
-    }
-    avdevice_free_list_devices(&devlist);
-    return device;
+    return devlist[0].first;
 }
 
 bool CameraDevice::getDefaultInputFormat()
@@ -179,19 +166,23 @@ bool CameraDevice::getDefaultInputFormat()
 
     avdevice_register_all();
 
-    // Linux
+#ifdef Q_OS_LINUX
     if ((iformat = av_find_input_format("v4l2")))
         return true;
+#endif
 
-    // Windows
+#ifdef Q_OS_WIN
     if ((iformat = av_find_input_format("dshow")))
         return true;
+    if ((iformat = av_find_input_format("vfwcap")))
+#endif
 
-    // Mac
+#ifdef Q_OS_OSX
     if ((iformat = av_find_input_format("avfoundation")))
         return true;
     if ((iformat = av_find_input_format("qtkit")))
         return true;
+#endif
 
     qWarning() << "No valid input format found";
     return false;

src/video/cameradevice.h

@@ -37,7 +37,7 @@ public:
 private:
     CameraDevice(const QString devName, AVFormatContext *context);
     static bool getDefaultInputFormat(); ///< Sets CameraDevice::iformat, returns success/failure
-    static AVDeviceInfoList* getRawDeviceList();
+    static QVector<QPair<QString, QString> > getRawDeviceListGeneric(); ///< Uses avdevice_list_devices
 
 public:
     const QString devName; ///< Short name of the device