winrt: Fix artifact at the beginning of audio

The artifact was generated by the RIFF/WAV header that was passed into
the audio sink.

Pick-to: 6.6
Change-Id: I33133b069894fecf506eb67c4877306f9d4109b1
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

2 files changed, 15 insertions, 0 deletions

diff --git a/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.cpp b/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.cpp
index a680ffe..476bc15 100644
--- a/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.cpp
+++ b/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.cpp
@@ -117,6 +117,19 @@ qint64 AudioSource::readData(char *data, qint64 maxlen)
     bufferByteAccess->Buffer(&pbyte);
     pbyte += m_bufferOffset;
 
+    // Check and skip the RIFF header if present to prevent an audible
+    // click at the start of playback.
+    if (!m_riffHeaderChecked) {
+        m_riffHeaderChecked = true;
+        static const int WaveHeaderLength = 44;
+        const char *descriptor = reinterpret_cast<const char*>(pbyte);
+        if (maxlen >= WaveHeaderLength && !qstrncmp(descriptor, "RIFF", 4)) {
+            pbyte += WaveHeaderLength;
+            m_bufferOffset += WaveHeaderLength;
+            maxlen -= WaveHeaderLength;
+        }
+    }
+
     switch (m_pause) {
     case NoPause:
         break;
diff --git a/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.h b/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.h
index dbd9752..79fdf16 100644
--- a/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.h
+++ b/src/plugins/tts/winrt/qtexttospeech_winrt_audiosource.h
@@ -124,6 +124,8 @@ private:
     ComPtr<::Windows::Storage::Streams::IBufferByteAccess> bufferByteAccess;
     // The data in the IBuffer might be paritally consumed
     UINT32 m_bufferOffset = 0;
+    // RIFF header has been checked at the beginning of the stream
+    bool m_riffHeaderChecked = false;
 
     void populateBoundaries();
     QList<Boundary> boundaries;