Move creation of ffmpeg audio resampler to utils

The refactoring is needed for the implementation
of QPlatformAudioResampler in the next commits.

Pick-to: 6.5
Task-number: QTBUG-118099
Change-Id: I6372dcba41011717c78bd586adf6c38dba8466d9
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
(cherry picked from commit c2f4dae915b8d341a316739a12c0be81abfb836d)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>
(cherry picked from commit d4a863bc813e80b753c7e566646863ad489dc20d)

3 files changed, 91 insertions, 41 deletions

diff --git a/src/plugins/multimedia/ffmpeg/qffmpeg.cpp b/src/plugins/multimedia/ffmpeg/qffmpeg.cpp
index 73c6c6788..f5b97566a 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpeg.cpp
+++ b/src/plugins/multimedia/ffmpeg/qffmpeg.cpp
@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qffmpeg_p.h"
+#include "qaudioformat.h"
+#include "qffmpegmediaformatinfo_p.h"
 
 #include <qdebug.h>
 #include <qloggingcategory.h>
@@ -15,6 +17,7 @@
 extern "C" {
 #include <libavutil/pixdesc.h>
 #include <libavutil/samplefmt.h>
+#include <libavutil/opt.h>
 
 #ifdef Q_OS_DARWIN
 #include <libavutil/hwcontext_videotoolbox.h>
@@ -427,6 +430,70 @@ const AVPacketSideData *streamSideData(const AVStream *stream, AVPacketSideDataT
 #endif
 }
 
+ResampleAudioFormat::ResampleAudioFormat(const AVCodecParameters* codecPar)
+    : sampleFormat(AVSampleFormat(codecPar->format)), sampleRate(codecPar->sample_rate)
+{
+#if QT_FFMPEG_OLD_CHANNEL_LAYOUT
+    if (codecPar->channel_layout) {
+        channelLayoutMask = codecPar->channel_layout;
+    }
+    else {
+        const auto channelConfig =
+                QAudioFormat::defaultChannelConfigForChannelCount(codecPar->channels);
+        channelLayoutMask = QFFmpegMediaFormatInfo::avChannelLayout(channelConfig);
+    }
+#else
+    channelLayout = codecPar->ch_layout;
+#endif
+}
+
+ResampleAudioFormat::ResampleAudioFormat(const QAudioFormat& audioFormat)
+    : sampleFormat(QFFmpegMediaFormatInfo::avSampleFormat(audioFormat.sampleFormat()))
+    , sampleRate(audioFormat.sampleRate())
+{
+    const auto channelConfig = audioFormat.channelConfig() == QAudioFormat::ChannelConfigUnknown ?
+            QAudioFormat::defaultChannelConfigForChannelCount(audioFormat.channelCount()) :
+            audioFormat.channelConfig();
+
+    const auto mask = QFFmpegMediaFormatInfo::avChannelLayout(channelConfig);
+
+#if QT_FFMPEG_OLD_CHANNEL_LAYOUT
+    channelLayoutMask = mask;
+#else
+    av_channel_layout_from_mask(&channelLayout, mask);
+#endif
+}
+
+SwrContextUPtr createResampleContext(const ResampleAudioFormat& inputFormat,
+                                     const ResampleAudioFormat& outputFormat)
+{
+    SwrContext *resampler = nullptr;
+#if QT_FFMPEG_OLD_CHANNEL_LAYOUT
+    resampler = swr_alloc_set_opts(nullptr,
+                                   outputFormat.channelLayoutMask,
+                                   outputFormat.sampleFormat,
+                                   outputFormat.sampleRate,
+                                   inputFormat.channelLayoutMask,
+                                   inputFormat.sampleFormat,
+                                   inputFormat.sampleRate,
+                                   0,
+                                   nullptr);
+#else
+    swr_alloc_set_opts2(&resampler,
+                        &outputFormat.channelLayout,
+                        outputFormat.sampleFormat,
+                        outputFormat.sampleRate,
+                        &inputFormat.channelLayout,
+                        inputFormat.sampleFormat,
+                        inputFormat.sampleRate,
+                        0,
+                        nullptr);
+#endif
+
+    swr_init(resampler);
+    return SwrContextUPtr(resampler);
+}
+
 #ifdef Q_OS_DARWIN
 bool isCVFormatSupported(uint32_t cvFormat)
 {
diff --git a/src/plugins/multimedia/ffmpeg/qffmpeg_p.h b/src/plugins/multimedia/ffmpeg/qffmpeg_p.h
index b4db6e20d..27d5e723c 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpeg_p.h
+++ b/src/plugins/multimedia/ffmpeg/qffmpeg_p.h
@@ -27,6 +27,8 @@ extern "C" {
 
 QT_BEGIN_NAMESPACE
 
+class QAudioFormat;
+
 namespace QFFmpeg
 {
 
@@ -201,6 +203,24 @@ AVPixelFormat pixelFormatForHwDevice(AVHWDeviceType deviceType);
 
 const AVPacketSideData *streamSideData(const AVStream *stream, AVPacketSideDataType type);
 
+struct ResampleAudioFormat
+{
+    ResampleAudioFormat(const AVCodecParameters* codecPar);
+
+    ResampleAudioFormat(const QAudioFormat& audioFormat);
+
+#if QT_FFMPEG_OLD_CHANNEL_LAYOUT
+    uint64_t channelLayoutMask;
+#else
+    AVChannelLayout channelLayout;
+#endif
+    AVSampleFormat sampleFormat;
+    int sampleRate;
+};
+
+SwrContextUPtr createResampleContext(const ResampleAudioFormat& inputFormat,
+                                     const ResampleAudioFormat& outputFormat);
+
 #ifdef Q_OS_DARWIN
 bool isCVFormatSupported(uint32_t format);
 
diff --git a/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp b/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp
index f84aecfbc..c5c277213 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp
+++ b/src/plugins/multimedia/ffmpeg/qffmpegresampler.cpp
@@ -5,10 +5,6 @@
 #include "qffmpegmediaformatinfo_p.h"
 #include <qloggingcategory.h>
 
-extern "C" {
-#include <libavutil/opt.h>
-}
-
 static Q_LOGGING_CATEGORY(qLcResampler, "qt.multimedia.ffmpeg.resampler")
 
 QT_BEGIN_NAMESPACE
@@ -19,50 +15,17 @@ namespace QFFmpeg
 Resampler::Resampler(const Codec *codec, const QAudioFormat &outputFormat)
     : m_outputFormat(outputFormat)
 {
+    Q_ASSERT(codec);
+
     qCDebug(qLcResampler) << "createResampler";
     const AVStream *audioStream = codec->stream();
-    const auto *codecpar = audioStream->codecpar;
 
     if (!m_outputFormat.isValid())
         // want the native format
         m_outputFormat = QFFmpegMediaFormatInfo::audioFormatFromCodecParameters(audioStream->codecpar);
 
-    QAudioFormat::ChannelConfig config = m_outputFormat.channelConfig();
-    if (config == QAudioFormat::ChannelConfigUnknown)
-        config = QAudioFormat::defaultChannelConfigForChannelCount(m_outputFormat.channelCount());
-
-
-    qCDebug(qLcResampler) << "init resampler" << m_outputFormat.sampleRate() << config << codecpar->sample_rate;
-    SwrContext *resampler = nullptr;
-#if QT_FFMPEG_OLD_CHANNEL_LAYOUT
-    auto inConfig = codecpar->channel_layout;
-    if (inConfig == 0)
-        inConfig = QFFmpegMediaFormatInfo::avChannelLayout(QAudioFormat::defaultChannelConfigForChannelCount(codecpar->channels));
-    resampler = swr_alloc_set_opts(nullptr,  // we're allocating a new context
-                                   QFFmpegMediaFormatInfo::avChannelLayout(config),  // out_ch_layout
-                                   QFFmpegMediaFormatInfo::avSampleFormat(m_outputFormat.sampleFormat()),    // out_sample_fmt
-                                   m_outputFormat.sampleRate(),                // out_sample_rate
-                                   inConfig, // in_ch_layout
-                                   AVSampleFormat(codecpar->format),   // in_sample_fmt
-                                   codecpar->sample_rate,                // in_sample_rate
-                                   0,                    // log_offset
-                                   nullptr);
-#else
-    AVChannelLayout in_ch_layout = codecpar->ch_layout;
-    AVChannelLayout out_ch_layout = {};
-    av_channel_layout_from_mask(&out_ch_layout, QFFmpegMediaFormatInfo::avChannelLayout(config));
-    swr_alloc_set_opts2(&resampler,  // we're allocating a new context
-                        &out_ch_layout,
-                        QFFmpegMediaFormatInfo::avSampleFormat(m_outputFormat.sampleFormat()),
-                        m_outputFormat.sampleRate(),
-                        &in_ch_layout,
-                        AVSampleFormat(codecpar->format),
-                        codecpar->sample_rate,
-                        0,
-                        nullptr);
-#endif
-    swr_init(resampler);
-    m_resampler.reset(resampler);
+    m_resampler = createResampleContext(ResampleAudioFormat(audioStream->codecpar),
+                                        ResampleAudioFormat(m_outputFormat));
 }
 
 Resampler::~Resampler() = default;