Fix audio and video synchronization with ffmpeg backend

Set a correct output playback rate to the audio resampler.
The functionality will be tested after implementation mocks of audio output.

Task-number: QTBUG-105617
Change-Id: Iaed95ac12e5e75b55b2c09245aad45c32a885fdf
Reviewed-by: Lars Knoll <lars@knoll.priv.no>
(cherry picked from commit 5393dae58ed62ec765abfb846dcd33a7b2aaaac6)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

2 files changed, 15 insertions, 3 deletions

diff --git a/src/plugins/multimedia/ffmpeg/qffmpegdecoder.cpp b/src/plugins/multimedia/ffmpeg/qffmpegdecoder.cpp
index 66e2c28c3..f37a10174 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpegdecoder.cpp
+++ b/src/plugins/multimedia/ffmpeg/qffmpegdecoder.cpp
@@ -775,24 +775,35 @@ void AudioRenderer::updateOutput(const Codec *codec)
     format = QFFmpegMediaFormatInfo::audioFormatFromCodecParameters(audioStream->codecpar);
     format.setChannelConfig(dev.channelConfiguration());
 
+    initResempler(codec);
+
     audioSink = new QAudioSink(dev, format);
     audioSink->setVolume(output->volume());
 
     audioSink->setBufferSize(format.bytesForDuration(100000));
     audioDevice = audioSink->start();
+
     latencyUSecs = format.durationForBytes(audioSink->bufferSize()); // ### ideally get full latency
     qCDebug(qLcAudioRenderer) << "   -> have an audio sink" << audioDevice;
+}
 
+void AudioRenderer::initResempler(const Codec *codec)
+{
     // init resampler. It's ok to always do this, as the resampler will be a no-op if
     // formats agree.
     AVSampleFormat requiredFormat = QFFmpegMediaFormatInfo::avSampleFormat(format.sampleFormat());
 
 #if QT_FFMPEG_OLD_CHANNEL_LAYOUT
-    qCDebug(qLcAudioRenderer) << "init resampler" << requiredFormat << audioStream->codecpar->channels;
+    qCDebug(qLcAudioRenderer) << "init resampler" << requiredFormat
+                              << codec->stream()->codecpar->channels;
 #else
-    qCDebug(qLcAudioRenderer) << "init resampler" << requiredFormat << audioStream->codecpar->ch_layout.nb_channels;
+    qCDebug(qLcAudioRenderer) << "init resampler" << requiredFormat
+                              << codec->stream()->codecpar->ch_layout.nb_channels;
 #endif
-    resampler.reset(new Resampler(codec, format));
+
+    auto resamplerFormat = format;
+    resamplerFormat.setSampleRate(qRound(format.sampleRate() / playbackRate()));
+    resampler.reset(new Resampler(codec, resamplerFormat));
 }
 
 void AudioRenderer::freeOutput()
diff --git a/src/plugins/multimedia/ffmpeg/qffmpegdecoder_p.h b/src/plugins/multimedia/ffmpeg/qffmpegdecoder_p.h
index 0ca069105..01763911d 100644
--- a/src/plugins/multimedia/ffmpeg/qffmpegdecoder_p.h
+++ b/src/plugins/multimedia/ffmpeg/qffmpegdecoder_p.h
@@ -474,6 +474,7 @@ private slots:
 
 private:
     void updateOutput(const Codec *codec);
+    void initResempler(const Codec *codec);
     void freeOutput();
 
     void init() override;