darwin aout modules: fix mono playback (refs #13826)

This matches the ALSA implementation now.

(cherry picked from commit 4817603a4cd918673c3eaa130c903daa52807984)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/audio_output/audioqueue.c

@@ -144,7 +144,7 @@ static int Start(audio_output_t *p_aout, audio_sample_format_t *restrict fmt)
     if (error != noErr)
         return VLC_EGENERIC;
     fmt->i_format = VLC_CODEC_FL32;
-    fmt->i_physical_channels = AOUT_CHANS_STEREO;
+    fmt->i_original_channels = fmt->i_physical_channels = AOUT_CHANS_STEREO;
     aout_FormatPrepare(fmt);
     p_aout->sys->i_rate = fmt->i_rate;
 

modules/audio_output/audiounit_ios.c

@@ -200,7 +200,7 @@ static int StartAnalog(audio_output_t *p_aout, audio_sample_format_t *fmt)
     AudioStreamBasicDescription streamDescription;
     streamDescription.mSampleRate = fmt->i_rate;
     fmt->i_format = VLC_CODEC_FL32;
-    fmt->i_physical_channels = AOUT_CHANS_STEREO;
+    fmt->i_physical_channels = fmt->i_original_channels = AOUT_CHANS_STEREO;
     streamDescription.mFormatID = kAudioFormatLinearPCM;
     streamDescription.mFormatFlags = kAudioFormatFlagsNativeFloatPacked; // FL32
     streamDescription.mChannelsPerFrame = aout_FormatNbChannels(fmt);

modules/audio_output/auhal.c

@@ -635,6 +635,7 @@ static int StartAnalog(audio_output_t *p_aout, audio_sample_format_t *fmt)
         msg_Warn(p_aout, "device driver does not support kAudioDevicePropertyPreferredChannelLayout - using stereo fallback [%4.4s]", (char *)&err);
         fmt->i_physical_channels = AOUT_CHANS_STEREO;
     }
+    fmt->i_original_channels = fmt->i_physical_channels;
 
     msg_Dbg(p_aout, "selected %d physical channels for device output", aout_FormatNbChannels(fmt));
     msg_Dbg(p_aout, "VLC will output: %s", aout_FormatPrintChannels(fmt));