Add qt_real_to_fraction() helper function.

Private API meant to be used by plugins whose backends expect frame
rate values represented by a ratio.
The function implementation was moved from the AVFoundation plugin
to the QtMultimedia library.

Change-Id: I555b9d5da5ca3bae88992ed03501869fb731e45f
Reviewed-by: Christian Stromme <christian.stromme@theqtcompany.com>

6 files changed, 154 insertions, 46 deletions

diff --git a/src/multimedia/multimedia.pro b/src/multimedia/multimedia.pro
index ff47768ab..524952470 100644
--- a/src/multimedia/multimedia.pro
+++ b/src/multimedia/multimedia.pro
@@ -25,7 +25,8 @@ PRIVATE_HEADERS += \
     qmediaresourcepolicy_p.h \
     qmediaresourceset_p.h \
     qmediastoragelocation_p.h \
-    qmediaopenglhelper_p.h
+    qmediaopenglhelper_p.h \
+    qmultimediautils_p.h
 
 PUBLIC_HEADERS += \
     qmediabindableinterface.h \
@@ -52,7 +53,8 @@ SOURCES += \
     qmediaresourcepolicy_p.cpp \
     qmediaresourceset_p.cpp \
     qmediastoragelocation.cpp \
-    qmultimedia.cpp
+    qmultimedia.cpp \
+    qmultimediautils.cpp
 
 include(audio/audio.pri)
 include(camera/camera.pri)
diff --git a/src/multimedia/qmultimediautils.cpp b/src/multimedia/qmultimediautils.cpp
new file mode 100644
index 000000000..6635e755d
--- /dev/null
+++ b/src/multimedia/qmultimediautils.cpp
@@ -0,0 +1,81 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qmultimediautils_p.h"
+
+QT_BEGIN_NAMESPACE
+
+void qt_real_to_fraction(qreal value, int *numerator, int *denominator)
+{
+    if (!numerator || !denominator)
+        return;
+
+    const int dMax = 1000;
+    int n1 = 0, d1 = 1, n2 = 1, d2 = 1;
+    qreal mid = 0.;
+    while (d1 <= dMax && d2 <= dMax) {
+        mid = qreal(n1 + n2) / (d1 + d2);
+
+        if (qAbs(value - mid) < 0.000001) {
+            if (d1 + d2 <= dMax) {
+                *numerator = n1 + n2;
+                *denominator = d1 + d2;
+                return;
+            } else if (d2 > d1) {
+                *numerator = n2;
+                *denominator = d2;
+                return;
+            } else {
+                *numerator = n1;
+                *denominator = d1;
+                return;
+            }
+        } else if (value > mid) {
+            n1 = n1 + n2;
+            d1 = d1 + d2;
+        } else {
+            n2 = n1 + n2;
+            d2 = d1 + d2;
+        }
+    }
+
+    if (d1 > dMax) {
+        *numerator = n2;
+        *denominator = d2;
+    } else {
+        *numerator = n1;
+        *denominator = d1;
+    }
+}
+
+QT_END_NAMESPACE
diff --git a/src/multimedia/qmultimediautils_p.h b/src/multimedia/qmultimediautils_p.h
new file mode 100644
index 000000000..61bbb6008
--- /dev/null
+++ b/src/multimedia/qmultimediautils_p.h
@@ -0,0 +1,57 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QMULTIMEDIAUTILS_P_H
+#define QMULTIMEDIAUTILS_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API. It exists purely as an
+// implementation detail. This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtMultimedia/qmultimedia.h>
+
+QT_BEGIN_NAMESPACE
+
+Q_MULTIMEDIA_EXPORT void qt_real_to_fraction(qreal value, int *numerator, int *denominator);
+
+QT_END_NAMESPACE
+
+#endif // QMULTIMEDIAUTILS_P_H
+
diff --git a/src/plugins/avfoundation/camera/avfcamerautility.h b/src/plugins/avfoundation/camera/avfcamerautility.h
index 42005a502..64093645f 100644
--- a/src/plugins/avfoundation/camera/avfcamerautility.h
+++ b/src/plugins/avfoundation/camera/avfcamerautility.h
@@ -160,8 +160,6 @@ inline QSysInfo::MacVersion qt_OS_limit(QSysInfo::MacVersion osxVersion,
 
 typedef QPair<qreal, qreal> AVFPSRange;
 AVFPSRange qt_connection_framerates(AVCaptureConnection *videoConnection);
-typedef QPair<int, int> AVFRational;
-AVFRational qt_float_to_rational(qreal par, int limit);
 
 #if QT_MAC_PLATFORM_SDK_EQUAL_OR_ABOVE(__MAC_10_7, __IPHONE_7_0)
 
diff --git a/src/plugins/avfoundation/camera/avfcamerautility.mm b/src/plugins/avfoundation/camera/avfcamerautility.mm
index f45169d07..3668bb124 100644
--- a/src/plugins/avfoundation/camera/avfcamerautility.mm
+++ b/src/plugins/avfoundation/camera/avfcamerautility.mm
@@ -36,6 +36,7 @@
 
 #include <QtCore/qvector.h>
 #include <QtCore/qpair.h>
+#include <private/qmultimediautils_p.h>
 
 #include <functional>
 #include <algorithm>
@@ -77,42 +78,6 @@ AVFPSRange qt_connection_framerates(AVCaptureConnection *videoConnection)
     return newRange;
 }
 
-AVFRational qt_float_to_rational(qreal par, int limit)
-{
-    Q_ASSERT(limit > 0);
-
-    // In Qt we represent pixel aspect ratio
-    // as a rational number (we use QSize).
-    // AVFoundation describes dimensions in pixels
-    // and in pixels with width multiplied by PAR.
-    // Represent this PAR as a ratio.
-    int a = 0, b = 1, c = 1, d = 1;
-    qreal mid = 0.;
-    while (b <= limit && d <= limit) {
-        mid = qreal(a + c) / (b + d);
-
-        if (qAbs(par - mid) < 0.000001) {
-            if (b + d <= limit)
-                return AVFRational(a + c, b + d);
-            else if (d > b)
-                return AVFRational(c, d);
-            else
-                return AVFRational(a, b);
-        } else if (par > mid) {
-            a = a + c;
-            b = b + d;
-        } else {
-            c = a + c;
-            d = b + d;
-        }
-    }
-
-    if (b > limit)
-        return AVFRational(c, d);
-
-    return AVFRational(a, b);
-}
-
 #if QT_MAC_PLATFORM_SDK_EQUAL_OR_ABOVE(__MAC_10_7, __IPHONE_7_0)
 
 namespace {
@@ -264,10 +229,13 @@ QSize qt_device_format_pixel_aspect_ratio(AVCaptureDeviceFormat *format)
     if (!res.width || !resPAR.width)
         return QSize();
 
-    const AVFRational asRatio(qt_float_to_rational(resPAR.width > res.width
-                                                   ? res.width / qreal(resPAR.width)
-                                                   : resPAR.width / qreal(res.width), 200));
-    return QSize(asRatio.first, asRatio.second);
+    int n, d;
+    qt_real_to_fraction(resPAR.width > res.width
+                        ? res.width / qreal(resPAR.width)
+                        : resPAR.width / qreal(res.width),
+                        &n, &d);
+
+    return QSize(n, d);
 }
 
 AVCaptureDeviceFormat *qt_find_best_resolution_match(AVCaptureDevice *captureDevice,
diff --git a/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm b/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm
index 05f28898d..c5da1c343 100644
--- a/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm
+++ b/src/plugins/avfoundation/camera/avfcameraviewfindersettingscontrol.mm
@@ -45,6 +45,7 @@
 #include <QtCore/qvector.h>
 #include <QtCore/qdebug.h>
 #include <QtCore/qlist.h>
+#include <private/qmultimediautils_p.h>
 
 #include <algorithm>
 
@@ -129,8 +130,9 @@ CMTime qt_adjusted_frame_duration(AVFrameRateRange *range, qreal fps)
     if (fps >= range.maxFrameRate)
         return range.minFrameDuration;
 
-    const AVFRational timeAsRational(qt_float_to_rational(1. / fps, 1000));
-    return CMTimeMake(timeAsRational.first, timeAsRational.second);
+    int n, d;
+    qt_real_to_fraction(1. / fps, &n, &d);
+    return CMTimeMake(n, d);
 }
 
 void qt_set_framerate_limits(AVCaptureDevice *captureDevice,