Windows: Fix audio buffer sizes

Audio buffer sizes were being calculated in a way that could result
in buffer sizes that were not a multiple of the audio frame size.
For instance, a buffer with an odd number of bytes could be used for
holding 16-bit audio data, which would result in the audio data
contained on half of buffers received by applications being shifted
by half a sample, causing applications to misinterpret that audio data.

Pick-to: 6.3 6.2
Fixes: QTBUG-102843
Change-Id: I252384cb99fffca5e068b0b14e4be9b0469962ec
Reviewed-by: Piotr Srebrny <piotr.srebrny@qt.io>
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 5 insertions, 8 deletions

diff --git a/src/multimedia/windows/qwindowsaudiosource.cpp b/src/multimedia/windows/qwindowsaudiosource.cpp
index d86b27157..8523f9982 100644
--- a/src/multimedia/windows/qwindowsaudiosource.cpp
+++ b/src/multimedia/windows/qwindowsaudiosource.cpp
@@ -305,14 +305,11 @@ bool QWindowsAudioSource::open()
     if (!QWindowsAudioUtils::formatToWaveFormatExtensible(settings, wfx)) {
         qWarning("QAudioSource: open error, invalid format.");
     } else if (buffer_size == 0) {
-        buffer_size
-                = (settings.sampleRate()
-                * settings.channelCount()
-                * settings.bytesPerSample()
-                + 39) / 5;
-        period_size = buffer_size / 5;
+        period_size = settings.sampleRate() / 25 * settings.bytesPerFrame();
+        buffer_size = period_size * 5;
     } else {
-        period_size = buffer_size / 5;
+        if (int bpf = settings.bytesPerFrame())
+            period_size = bpf * (buffer_size / 5 / bpf);
     }
 
     if (period_size == 0) {
@@ -645,7 +642,7 @@ bool QWindowsAudioSource::deviceReady()
 
     if(pullMode) {
         // reads some audio data and writes it to QIODevice
-        read(0, buffer_size);
+        read(0, period_size * (buffer_size / period_size));
     } else {
         // emits readyRead() so user will call read() on QIODevice to get some audio data
         InputPrivate* a = qobject_cast<InputPrivate*>(audioSource);