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Hey everyone!
I was browsing around and trying to catch up and learn more about the audio frameworks for CocosDenshion and wrote up an article about a neat effect of level metering with the background music.
There's also a demo below!
Check it out and hopefully someone can make use of the classes I created. Give me some feedback if you have any.
http://fancyratstudios.com/2010/02/programming/cocos2d/fun-with-cocosdenshion-and-audio-metering/
Steve Oldmeadow
Administrator
It is not necessary to modify SimpleAudioEngine to get access to the CDAudioManager instance, it is safe to access it directly via [CDAudioManager sharedManager] after SimpleAudioEngine is initialised.
I'm also trying to discourage people from constantly accessing the shared instances via the shared... methods, particularly in code that is called frequently such as the tick methods in your example.
The code below is more along the lines of what I think is best practice, of course sae, cdam and bgm would likely be defined as class level variables on the game layer.
SimpleAudioEngine *sae = [SimpleAudioEngine sharedEngine];//Will init the SimpleAudioEngine
if (sae) {
CDAudioManager *cdam = [CDAudioManager sharedManager];
if (cdam) {
[cdam setResignBehavior: kAMRBStop autoHandle:YES];
AVAudioPlayer *bgm = cdam.backgroundMusic;
}
}Hmm...
Right now the [CDAudioManager sharedManager] seems to return nil for the trunk 1767
What I'm doing is replacing line 38 of AudioVisualization.m with
[SimpleAudioEngine sharedEngine];
if([[SimpleAudioEngine sharedEngine] isBackgroundMusicPlaying]){
audioPlayer_ = [CDAudioManager sharedManager].backgroundMusic;
audioPlayer_.meteringEnabled = YES;Taking a look at SimpleAudioEngine, I see that on init line 57
am = [[CDAudioManager alloc] init:kAudioManagerFxPlusMusicIfNoOtherAudio channelGroupDefinitions:channelGroups channelGroupTotal:1];Would that also setup the shared instance of CDAudioManager? or just allocate mem for 'am'.
Steve Oldmeadow
Administrator
Yes, that code used to set up the shared instance. It looks like someone has changed the way the singleton is set up (probably so clang doesn't complain) and broken things.
I don't have time to look at it right now, so leave your code as it is. In the future it will be safe to access CDAudioManager through the shared instance. My intention is to never expose the CDAudioManager via the SimpleAudioEngine API as it would be confusing to newbies that struggle with the API as it is.
Steve Oldmeadow
Administrator
This is in my version of CDAudioManager
+ (id) alloc
{
@synchronized(self) {
NSAssert(sharedManager == nil, @"Attempted to allocate a second instance of a singleton.");
sharedManager = [super alloc];
return sharedManager;
}
return nil;
}and this is the version in the cocos2d head.
+ (id) alloc
{
@synchronized(self) {
NSAssert(sharedManager == nil, @"Attempted to allocate a second instance of a singleton.");
return [super alloc];
}
return nil;
}
Steve Oldmeadow
Administrator
Just checked. Riq made the change in October as part of cleaning up Singletons for Clang compatibility. I'll need to modify SimpleAudioEngine so that it initialises the CDAudioManager differently, I'll do it Monday.
Thanks for the article BTW - it is nice to have a few more Denshion examples.
I just finished creating a short little demo video for youtube in case anyone would like to see the effect without having to actually download and try the code.
| Get the Video Player |
Steve Oldmeadow
Administrator
Access to the CDAudioManager shared instance when using SimpleAudioEngine is fixed up in r1769.
Nice video, nice tutorial!
Box2DSmiley
Member
Hi,
This looks really awesome!
Is it possible to create an audio visualizer app for the iphone using the iPod library, or by listening to the playing music?
I haven't really seen any of this on the app store (besides Audiogasm, which uses the mic to monitor the sound levels... ) - is apple limiting this kind of applications?
Steve Oldmeadow
Administrator
@Box2DSmiley - as far as I know you can't do it. You certainly can't do it with the MPMediaPlayer stuff or AVAudioPlayer.
There are some new 4.x APIs that may hold some promise though but I haven't had time to investigate.
@Steve-Oldmeadow is that because the iPod library is outside of the app bundle?
Steve Oldmeadow
Administrator
@hm50 - partly, but the main issue is Apple haven't provided the necessary APIs. From comments I've seen from Apple engineers in the dev forums they are not against the idea. Like I said before, some of the new AV* classes in 4.x might provide a means of doing it.
One of the WWDC 2010 demos was accessing individual frames of a video from the iPod library so accessing audio data of songs in the iPod library seems a possibility. There is a lot of new functionality to support video editing, part of which is the audio track. There is lots to investigate and it might not all be there until 4.1.
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