Diese mir helfen: AVAudioEngine and Multiroute, und diese: Audio Session and Multiroute Audio in iOS.
In meinem Fall verwende ich zwei Methoden zu implementieren:
ersten fordert die MultiRoute Kategorie
[_session setCategory:AVAudioSessionCategoryMultiRoute error:nil];
method1: setup channelAssignments von AVAudioPlayer:
// My hardware has 4 output channels
if (_outputPortChannels.count == 4) {
AVAudioSessionChannelDescription *desiredChannel1 = [_outputPortChannels objectAtIndex:2];
AVAudioSessionChannelDescription *desiredChannel2 = [_outputPortChannels objectAtIndex:3];
// Create an array of desired channels
NSArray *channelDescriptions = [NSArray arrayWithObjects:desiredChannel1, desiredChannel2, nil];
// Assign the channels
_avAudioPlayer1.channelAssignments = channelDescriptions;
NSLog(@"_player.channelAssignments: %@", _avAudioPlayer1.channelAssignments);
// Play audio to output channel3, channel4
[_avAudioPlayer1 play];
}
method2: Custom-Channel Karte
// Get channel map indices based on user specified channelNames
NSMutableArray *channelMapIndices = [self getOutputChannelMapIndices:_inChannelNames];
NSAssert(channelMapIndices && channelMapIndices.count > 0, @"Error getting indices for user specified channel names!");
// AVAudioEngine setup
_engine = [[AVAudioEngine alloc] init];
_output = _engine.outputNode;
_mixer = _engine.mainMixerNode;
_player = [[AVAudioPlayerNode alloc] init];
[_engine attachNode:_player];
// open the file to play
NSString *path1 = [[NSBundle mainBundle] pathForResource:@"yujian" ofType:@"mp3"];
NSURL *songURL1 = [NSURL fileURLWithPath:path1];
_songFile = [[AVAudioFile alloc] initForReading:songURL1 error:nil];
// create output channel map
SInt32 source1NumChannels = (SInt32)_songFile.processingFormat.channelCount;
// I use constant map
// Play audio to output channel3, channel4
SInt32 outputChannelMap[4] = {-1, -1, 0, 1};
// This will play audio to output channel1, channel2
//SInt32 outputChannelMap[4] = {0, 1, -1, -1};
// set channel map on outputNode AU
UInt32 propSize = (UInt32)sizeof(outputChannelMap);
OSStatus err = AudioUnitSetProperty(_output.audioUnit, kAudioOutputUnitProperty_ChannelMap, kAudioUnitScope_Global, 1, outputChannelMap, propSize);
NSAssert(noErr == err, @"Error setting channel map! %d", (int)err);
// make connections
AVAudioChannelLayout *channel1Layout = [[AVAudioChannelLayout alloc] initWithLayoutTag:kAudioChannelLayoutTag_DiscreteInOrder | (UInt32)source1NumChannels];
AVAudioFormat *format1 = [[AVAudioFormat alloc] initWithStreamDescription:_songFile.processingFormat.streamDescription channelLayout:channel1Layout];
[_engine connect:_player to:_mixer format:format1];
[_engine connect:_mixer to:_output format:format1];
// schedule the file on player
[_player scheduleFile:_songFile atTime:nil completionHandler:nil];
// start engine and player
if (!_engine.isRunning) {
[_engine startAndReturnError:nil];
}
[_player play];
Es funktioniert für mich.
Wie machen Sie eine Kanalzuordnung für Eingänge? Was ist, wenn ich einen externen USB-Mikrofoneingang habe und von Kanal 5 lesen möchte? Es scheint nur kAudioOutputUnitProperty_ChannelMap und keine kAudioInputUnitProperty_ChannelMap zu geben – jaybers