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POHow do I audio crossfade using cocoalibspotify?
 

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  1. POHow do I audio crossfade using cocoalibspotify?
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    <p>I'd like to crossfade from one track to the next in a Spotify enabled app. Both tracks are Spotify tracks, and since only one data stream at a time can come from Spotify, I suspect I need to buffer (I think I can read ahead 1.5 x playback speed) the last few seconds of the first track, start the stream for track two, fade out one and fade in two using an AudioUnit.</p> <p>I've reviewed sample apps: Viva - <a href="https://github.com/iKenndac/Viva" rel="nofollow noreferrer">https://github.com/iKenndac/Viva</a> SimplePlayer with EQ - <a href="https://github.com/iKenndac/SimplePlayer-with-EQ" rel="nofollow noreferrer">https://github.com/iKenndac/SimplePlayer-with-EQ</a> and tried to get my mind around the SPCircularBuffer, but I still need help. Could someone point me to another example or help bullet-point a track crossfade game plan? </p> <p>Update: Thanks to iKenndac, I'm about 95% there. I'll post what I have so far:</p> <p>in SPPlaybackManager.m: initWithPlaybackSession:(SPSession *)aSession {</p> <p>added:</p> <pre><code>self.audioController2 = [[SPCoreAudioController alloc] init]; self.audioController2.delegate = self; </code></pre> <p>and in</p> <pre><code>- (void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary *)change context:(void *)context { ... self.audioController.audioOutputEnabled = self.playbackSession.isPlaying; // for crossfade, add self.audioController2.audioOutputEnabled = self.playbackSession.isPlaying; </code></pre> <p>and added a new method based on playTrack</p> <pre><code>-(void)crossfadeTrack:(SPTrack *)aTrack callback:(SPErrorableOperationCallback)block { // switch audiocontroller from current to other if (self.playbackSession.audioDeliveryDelegate == self.audioController) { self.playbackSession.audioDeliveryDelegate = self.audioController2; self.audioController2.delegate = self; self.audioController.delegate = nil; } else { self.playbackSession.audioDeliveryDelegate = self.audioController; self.audioController.delegate = self; self.audioController2.delegate = nil; } if (aTrack.availability != SP_TRACK_AVAILABILITY_AVAILABLE) { if (block) block([NSError spotifyErrorWithCode:SP_ERROR_TRACK_NOT_PLAYABLE]); self.currentTrack = nil; } self.currentTrack = aTrack; self.trackPosition = 0.0; [self.playbackSession playTrack:self.currentTrack callback:^(NSError *error) { if (!error) self.playbackSession.playing = YES; else self.currentTrack = nil; if (block) { block(error); } }]; } </code></pre> <p>this starts a timer for crossfade</p> <p>crossfadeTimer = [NSTimer scheduledTimerWithTimeInterval: 0.5 target: self selector: @selector ( crossfadeCountdown) userInfo: nil repeats: YES];</p> <p>And in order to keep the first track playing after its data has loaded in SPCoreAudioController.m I changed target buffer length:</p> <pre><code>static NSTimeInterval const kTargetBufferLength = 20; </code></pre> <p>and in SPSession.m : end_of_track(sp_session *session) {</p> <p>I removed</p> <pre><code>// sess.playing = NO; </code></pre> <p>I call preloadTrackForPlayback: about 15 seconds before end of track, then crossfadeTrack: at 10 seconds before. </p> <p>Then set crossfadeCountdownTime = [how many seconds you want the crossfade]*2;</p> <p>I fade volume over the crosssfade with:</p> <pre><code> - (void) crossfadeCountdown { [UIAppDelegate.playbackSPManager setVolume:(1- (((float)crossfadeCountdownTime/ (thisCrossfadeSeconds*2.0)) *0.2) )]; crossfadeCountdownTime -= 0.5; if (crossfadeCountdownTime == 1.0) { NSLog(@"Crossfade countdown done"); crossfadeCountdownTime = 0; [crossfadeTimer invalidate]; crossfadeTimer = nil; [UIAppDelegate.playbackSPManager setVolume:1.0]; } } </code></pre> <p>I'll keep working on it, and update if I can make it better. Thanks again to iKenndac for his always spot-on help! </p>
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