AVAudioPlayer 声音文件混合时播放不同步 - iPhone
我正在尝试使用 AVAudioPlayer 实例播放 6 个独立的 .mp3 声音文件。 声音同时播放，但似乎播放不同步或 以略有不同的速度。有谁知道为什么会这样？
这是我初始化声音的方法：
NSURL *musicurl = [[NSURL alloc] initFileURLWithPath:[[NSBundle mainBundle] pathForResource: @"SoundLoop" ofType: @"mp3"]];
music = [[AVAudioPlayer alloc] initWithContentsOfURL: musicurl error: nil];
[musicurl release];
music.numberOfLoops = -1; // Loop indefinately
music.currentTime = 0; // start at beginning
music.volume = 1.0;
music.meteringEnabled = YES;
这是我的 AudioSession 代码：
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
audioSession.delegate = self;
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
[[AVAudioSession sharedInstance] setPreferredHardwareSampleRate:44100 error:nil];
[[AVAudioSession sharedInstance] setPreferredIOBufferDuration:30 error:nil];
UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
Float32 hardvol = 1.0;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(sessionCategory), &sessionCategory);
AudioSessionSetProperty(kAudioSessionProperty_CurrentHardwareOutputVolume, sizeof(hardvol), &hardvol);
UInt32 doSetProperty = 1;
AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(doSetProperty), &doSetProperty);
[[AVAudioSession sharedInstance] setActive:YES error: nil];
它可能与声音的比特率有关吗？或者我正在使用 .mp3？
谢谢。
I am trying to play 6 seperate .mp3 sound files using instances of AVAudioPlayer.
The sounds are playing at the same time but they seem to be playing out of sync or
at slightly different speeds. Does anyone know why this may be?
Here is how I initialize a sound:
NSURL *musicurl = [[NSURL alloc] initFileURLWithPath:[[NSBundle mainBundle] pathForResource: @"SoundLoop" ofType: @"mp3"]];
music = [[AVAudioPlayer alloc] initWithContentsOfURL: musicurl error: nil];
[musicurl release];
music.numberOfLoops = -1; // Loop indefinately
music.currentTime = 0; // start at beginning
music.volume = 1.0;
music.meteringEnabled = YES;
and here is my AudioSession code:
AVAudioSession *audioSession = [AVAudioSession sharedInstance];
audioSession.delegate = self;
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
[[AVAudioSession sharedInstance] setPreferredHardwareSampleRate:44100 error:nil];
[[AVAudioSession sharedInstance] setPreferredIOBufferDuration:30 error:nil];
UInt32 sessionCategory = kAudioSessionCategory_MediaPlayback;
Float32 hardvol = 1.0;
AudioSessionSetProperty(kAudioSessionProperty_AudioCategory, sizeof(sessionCategory), &sessionCategory);
AudioSessionSetProperty(kAudioSessionProperty_CurrentHardwareOutputVolume, sizeof(hardvol), &hardvol);
UInt32 doSetProperty = 1;
AudioSessionSetProperty(kAudioSessionProperty_OverrideCategoryMixWithOthers, sizeof(doSetProperty), &doSetProperty);
[[AVAudioSession sharedInstance] setActive:YES error: nil];
Could it possibly have anything to do with the bit rates of the sounds? or that I am using .mp3?
Thanks.
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我通过使用 AVAudioPlayer 类的 playAtTime: 方法找到了这个问题的解决方案：
使用此方法将允许所有声音异步同步播放。
I found the solution to this problem by using the playAtTime: method of the AVAudioPlayer class:
Using this will allow all the sounds to play asynchronously and in sync.
您应该查看多媒体编程指南。 “使用音频”部分有大量有用的信息。
http://developer.apple.com/ Library/ios/#documentation/AudioVideo/Conceptual/MultimediaPG/Introduction/Introduction.html
这听起来与您的问题有关：
这里还有一点声称你正在做的事情应该是可能的，但苹果似乎正在用“处理器效率最高的多重播放”线提出警告。我认为，如果处理器紧张，就会导致无法及时完美地保持事物。
在调试方面，您应该从两个音频声音开始，看看是否有问题。然后一直到 6，并找出是否有一个明显的点开始出现问题。我还会找到（或制作）一些 Apple 推荐的格式（PCM 或 IMA4）的音轨，并对这些进行相同的测试。执行这两件事应该可以帮助您缩小实际问题的范围。
You should check out the MultiMedia Programming Guide. The "Using Audio" section has tons of helpful information.
http://developer.apple.com/library/ios/#documentation/AudioVideo/Conceptual/MultimediaPG/Introduction/Introduction.html
This sounds like it relates to your issue:
Here's another bit that claims what you are doing should be possible but it seems like Apple is throwing in a caveat with "the most processor-efficient multiple playback" line. I would think that if the processor is strained that would lend itself to not keeping things perfectly in time.
In terms of debugging, you should start with two audio sounds and see if there is an issue. Then work your way up to the 6 and figure out if there is a distinct point at which the problem starts to occur. I would also find (or make) some audio tracks in the formats that Apple recommends (PCM or IMA4) and do the same testing with those. Doing these two things should help you narrow down what the actual problem is.