[Bug 732896] New: iOS: AudioUnit on iOS produces echo with in/out streams

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=732896
  GStreamer | gst-plugins-good | 1.x

           Summary: iOS: AudioUnit on iOS produces echo with in/out
                    streams
    Classification: Platform
           Product: GStreamer
           Version: 1.x
        OS/Version: Mac OS
            Status: UNCONFIRMED
          Severity: normal
          Priority: Normal
         Component: gst-plugins-good
        AssignedTo: gstreamer-bugs at lists.freedesktop.org
        ReportedBy: elio.francesconi at gmail.com
         QAContact: gstreamer-bugs at lists.freedesktop.org
     GNOME version: ---


The osxaudiosrc plugin is Remote I/O unit it is not suited for VoIP purpose
because no echo cancellator.
According to the Apple documentation, The Voice-Processing I/O unit extends the
Remote I/O unit by adding acoustic echo cancelation for use in a VoIP or
voice-chat application.
https://developer.apple.com/library/ios/documentation/MusicAudio/Conceptual/AudioUnitHostingGuide_iOS/AudioUnitHostingFundamentals/AudioUnitHostingFundamentals.html

To use Voice-rocessing I/O unit I did these changes:
in gstosxcoreaudioremoteio.c 

static gboolean
gst_core_audio_open_impl (GstCoreAudio * core_audio)
{
  return gst_core_audio_open_device (core_audio,
kAudioUnitSubType_VoiceProcessingIO,
                                       "VoiceProcessingIO");
  //return gst_core_audio_open_device (core_audio, kAudioUnitSubType_RemoteIO,
  //    "RemoteIO");
}

This patch was not enough to solve the issue because I received status = -50
after some calls of AudioUnitRender in getosxaudiosrc.c, it seems
AudioUnitRender modifies 
buf->core_audio->recBufferList->mBuffers[0].mDataByteSize based on data
returned, so before call AudioUnitRender it requires to set mDataByteSize today
I’ve created mine osxaudio plugin with these changes, hardcoding "bytes per
frame” and “channels” and solved my problem, I did’d check the buffer allocated
because it’s big enough.

buf->core_audio->recBufferList->mNumberBuffers=1;
buf->core_audio->recBufferList->mBuffers[0].mDataByteSize=inNumberFrames*4/*where
4 is bytes per frame*/;
buf->core_audio->recBufferList->mBuffers[0].mNumberChannels=1 /*num of
channels*/;
status = AudioUnitRender (buf->core_audio->audiounit, ioActionFlags,
      inTimeStamp, inBusNumber, inNumberFrames,
buf->core_audio->recBufferList);

  if (status) {
    GST_WARNING_OBJECT (buf, "AudioUnitRender returned %d", (int) status);
    return status;
  }

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