From 3b3df06195ad94588b4b1d2d9a8ddb3d9eba84c6 Mon Sep 17 00:00:00 2001
From: Chris Robinson <chris.kcat@gmail.com>
Date: Fri, 30 Jul 2021 06:13:54 -0700
Subject: Be more robust with unexpected channel counts

---
 alc/backends/winmm.cpp | 27 +++++++++++++--------------
 1 file changed, 13 insertions(+), 14 deletions(-)

(limited to 'alc/backends/winmm.cpp')

diff --git a/alc/backends/winmm.cpp b/alc/backends/winmm.cpp
index 42aee313..5a2f00f8 100644
--- a/alc/backends/winmm.cpp
+++ b/alc/backends/winmm.cpp
@@ -181,7 +181,7 @@ FORCE_ALIGN int WinMMPlayback::mixerProc()
     SetRTPriority();
     althrd_setname(MIXER_THREAD_NAME);
 
-    const size_t frame_step{mDevice->channelsFromFmt()};
+    const size_t frame_step{mDevice->bytesFromFmt() * mFormat.nChannels};
 
     while(!mKillNow.load(std::memory_order_acquire)
         && mDevice->Connected.load(std::memory_order_acquire))
@@ -196,7 +196,7 @@ FORCE_ALIGN int WinMMPlayback::mixerProc()
         size_t widx{mIdx};
         do {
             WAVEHDR &waveHdr = mWaveBuffer[widx];
-            widx = (widx+1) % mWaveBuffer.size();
+            if(++widx == mWaveBuffer.size()) widx = 0;
 
             mDevice->renderSamples(waveHdr.lpData, mDevice->UpdateSize, frame_step);
             mWritable.fetch_sub(1, std::memory_order_acq_rel);
@@ -223,9 +223,10 @@ void WinMMPlayback::open(const char *name)
             name};
     auto DeviceID = static_cast<UINT>(std::distance(PlaybackDevices.cbegin(), iter));
 
+    DevFmtType fmttype{mDevice->FmtType};
 retry_open:
     WAVEFORMATEX format{};
-    if(mDevice->FmtType == DevFmtFloat)
+    if(fmttype == DevFmtFloat)
     {
         format.wFormatTag = WAVE_FORMAT_IEEE_FLOAT;
         format.wBitsPerSample = 32;
@@ -233,7 +234,7 @@ retry_open:
     else
     {
         format.wFormatTag = WAVE_FORMAT_PCM;
-        if(mDevice->FmtType == DevFmtUByte || mDevice->FmtType == DevFmtByte)
+        if(fmttype == DevFmtUByte || fmttype == DevFmtByte)
             format.wBitsPerSample = 8;
         else
             format.wBitsPerSample = 16;
@@ -250,9 +251,9 @@ retry_open:
         reinterpret_cast<DWORD_PTR>(this), CALLBACK_FUNCTION)};
     if(res != MMSYSERR_NOERROR)
     {
-        if(mDevice->FmtType == DevFmtFloat)
+        if(fmttype == DevFmtFloat)
         {
-            mDevice->FmtType = DevFmtShort;
+            fmttype = DevFmtShort;
             goto retry_open;
         }
         throw al::backend_exception{al::backend_error::DeviceError, "waveOutOpen failed: %u", res};
@@ -303,7 +304,7 @@ bool WinMMPlayback::reset()
     }
 
     uint chanmask{};
-    if(mFormat.nChannels == 2)
+    if(mFormat.nChannels >= 2)
     {
         mDevice->FmtChans = DevFmtStereo;
         chanmask = SPEAKER_FRONT_LEFT | SPEAKER_FRONT_RIGHT;
@@ -320,7 +321,7 @@ bool WinMMPlayback::reset()
     }
     setChannelOrderFromWFXMask(chanmask);
 
-    uint BufferSize{mDevice->UpdateSize * mDevice->frameSizeFromFmt()};
+    uint BufferSize{mDevice->UpdateSize * mFormat.nChannels * mDevice->bytesFromFmt()};
 
     al_free(mWaveBuffer[0].lpData);
     mWaveBuffer[0] = WAVEHDR{};
@@ -340,9 +341,8 @@ bool WinMMPlayback::reset()
 void WinMMPlayback::start()
 {
     try {
-        std::for_each(mWaveBuffer.begin(), mWaveBuffer.end(),
-            [this](WAVEHDR &waveHdr) -> void
-            { waveOutPrepareHeader(mOutHdl, &waveHdr, sizeof(WAVEHDR)); });
+        for(auto &waveHdr : mWaveBuffer)
+            waveOutPrepareHeader(mOutHdl, &waveHdr, sizeof(WAVEHDR));
         mWritable.store(static_cast<uint>(mWaveBuffer.size()), std::memory_order_release);
 
         mKillNow.store(false, std::memory_order_release);
@@ -362,9 +362,8 @@ void WinMMPlayback::stop()
 
     while(mWritable.load(std::memory_order_acquire) < mWaveBuffer.size())
         mSem.wait();
-    std::for_each(mWaveBuffer.begin(), mWaveBuffer.end(),
-        [this](WAVEHDR &waveHdr) -> void
-        { waveOutUnprepareHeader(mOutHdl, &waveHdr, sizeof(WAVEHDR)); });
+    for(auto &waveHdr : mWaveBuffer)
+        waveOutUnprepareHeader(mOutHdl, &waveHdr, sizeof(WAVEHDR));
     mWritable.store(0, std::memory_order_release);
 }
 
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