Hi,
I just started to develop audio unit hosting support in my application.
Offline rendering seems to work except that I hear no output, but why?
I suspect with the player goes something wrong.
I connect to CoreAudio in a different location in the code.
Here are some error messages I faced so far:
2025-08-14 19:42:04.132930+0200 com.gsequencer.GSequencer[34358:18611871] [avae] AVAudioEngineGraph.mm:4668 Can't retrieve source node to play sequence because there is no output node!
2025-08-14 19:42:04.151171+0200 com.gsequencer.GSequencer[34358:18611871] [avae] AVAudioEngineGraph.mm:4668 Can't retrieve source node to play sequence because there is no output node!
2025-08-14 19:43:08.344530+0200 com.gsequencer.GSequencer[34358:18614927] AUAudioUnit.mm:1417 Cannot set maximumFramesToRender while render resources allocated.
2025-08-14 19:43:08.346583+0200 com.gsequencer.GSequencer[34358:18614927] [avae] AVAEInternal.h:104 [AVAudioSequencer.mm:121:-[AVAudioSequencer(AVAudioSequencer_Player) startAndReturnError:]: (impl->Start()): error -10852
** (<unknown>:34358): WARNING **: 19:43:08.346: error during audio sequencer start - -10852
I have implemented an AVAudioEngine based AudioUnit host. Here I instantiate player and effect:
/* audio engine */
audio_engine = [[AVAudioEngine alloc] init];
fx_audio_unit_audio->audio_engine = (gpointer) audio_engine;
av_format = (AVAudioFormat *) fx_audio_unit_audio->av_format;
/* av audio player node */
av_audio_player_node = [[AVAudioPlayerNode alloc] init];
/* av audio unit */
av_audio_unit_effect = [[AVAudioUnitEffect alloc] initWithAudioComponentDescription:[((AVAudioUnitComponent *) AGS_AUDIO_UNIT_PLUGIN(base_plugin)->component) audioComponentDescription]];
av_audio_unit = (AVAudioUnit *) av_audio_unit_effect;
fx_audio_unit_audio->av_audio_unit = av_audio_unit;
/* audio sequencer */
av_audio_sequencer = [[AVAudioSequencer alloc] initWithAudioEngine:audio_engine];
fx_audio_unit_audio->av_audio_sequencer = (gpointer) av_audio_sequencer;
/* output node */
[[AVAudioOutputNode alloc] init];
/* audio player and audio unit */
[audio_engine attachNode:av_audio_player_node];
[audio_engine attachNode:av_audio_unit];
[audio_engine connect:av_audio_player_node to:av_audio_unit format:av_format];
[audio_engine connect:av_audio_unit to:[audio_engine outputNode] format:av_format];
ns_error = NULL;
[audio_engine enableManualRenderingMode:AVAudioEngineManualRenderingModeOffline
format:av_format
maximumFrameCount:buffer_size error:&ns_error];
if(ns_error != NULL &&
[ns_error code] != noErr){
g_warning("enable manual rendering mode error - %d", [ns_error code]);
}
ns_error = NULL;
[[av_audio_unit AUAudioUnit] allocateRenderResourcesAndReturnError:&ns_error];
if(ns_error != NULL &&
[ns_error code] != noErr){
g_warning("Audio Unit allocate render resources returned error - ErrorCode %d", [ns_error code]);
}
Then I render in a dedicated thread.
ns_error = NULL;
[audio_engine startAndReturnError:&ns_error];
if(ns_error != NULL &&
[ns_error code] != noErr){
g_warning("error during audio engine start - %d", [ns_error code]);
}
[av_audio_sequencer prepareToPlay];
ns_error = NULL;
[av_audio_sequencer startAndReturnError:&ns_error];
if(ns_error != NULL &&
[ns_error code] != noErr){
g_warning("error during audio sequencer start - %d", [ns_error code]);
}
[av_audio_player_node play];
while(is_running){
/* pre sync */
/* IO buffers */
av_output_buffer = (AVAudioPCMBuffer *) scope_data->av_output_buffer;
av_input_buffer = (AVAudioPCMBuffer *) scope_data->av_input_buffer;
/* fill input buffer */
/* schedule av input buffer */
frame_position = 0; // (gint64) ((note_offset * absolute_delay) + delay_counter) * buffer_size;
av_audio_player_node = (AVAudioPlayerNode *) fx_audio_unit_audio->av_audio_player_node;
AVAudioTime *av_audio_time = [[AVAudioTime alloc] initWithHostTime:frame_position sampleTime:frame_position atRate:((double) samplerate)];
[av_audio_player_node scheduleBuffer:av_input_buffer atTime:av_audio_time options:0 completionHandler:nil];
/* render */
ns_error = NULL;
status = [audio_engine renderOffline:AGS_FX_AUDIO_UNIT_AUDIO_FIXED_BUFFER_SIZE toBuffer:av_output_buffer error:&ns_error];
if(ns_error != NULL &&
[ns_error code] != noErr){
g_warning("render offline error - %d", [ns_error code]);
}
}
regards, Joël
