iOS SoundTouch 框架 BPM 检测示例

Question

我在网上搜索过，找不到关于如何使用 SoundTouch library 的教程。用于节拍检测。

(注意:在此之前我没有 C++ 经验。我知道 C、Objective-C 和 Java。所以我可能搞砸了一些，但它编译了。)

我添加了 framework到我的项目并设法编译以下内容:

NSString *path = [[NSBundle mainBundle] pathForResource:@"song" ofType:@"wav"];

NSData *data = [NSData dataWithContentsOfFile:path];

player =[[AVAudioPlayer alloc] initWithData:data error:NULL];

player.volume = 1.0;

player.delegate = self;

[player prepareToPlay];
[player play];

NSUInteger len = [player.data length]; // Get the length of the data

soundtouch::SAMPLETYPE sampleBuffer[len]; // Create buffer array

[player.data getBytes:sampleBuffer length:len]; // Copy the bytes into the buffer

soundtouch::BPMDetect *BPM = new soundtouch::BPMDetect(player.numberOfChannels, [[player.settings valueForKey:@"AVSampleRateKey"] longValue]); // This is working (tested)

BPM->inputSamples(sampleBuffer, len); // Send the samples to the BPM class

NSLog(@"Beats Per Minute = %f", BPM->getBpm()); // Print out the BPM - currently returns 0.00 for errors per documentation

inputSamples(*samples, numSamples) 歌曲字节信息让我很困惑。

如何从歌曲文件中获取这些信息？

我尝试使用 memcpy() 但它似乎不起作用。

有人有什么想法吗？

Answer 1

经过几个小时的调试和阅读网络上有限的文档，我在绊倒这个之前修改了一些东西:你需要将 numSamples 除以 numberOfChannels 在inputSamples() 函数。

我的最终代码是这样的:

NSString *path = [[NSBundle mainBundle] pathForResource:@"song" ofType:@"wav"];

NSData *data = [NSData dataWithContentsOfFile:path];

player =[[AVAudioPlayer alloc] initWithData:data error:NULL];

player.volume = 1.0;    // optional to play music

player.delegate = self;

[player prepareToPlay]; // optional to play music
[player play];          // optional to play music

NSUInteger len = [player.data length];

soundtouch::SAMPLETYPE sampleBuffer[len];

[player.data getBytes:sampleBuffer length:len];

soundtouch::BPMDetect BPM(player.numberOfChannels, [[player.settings valueForKey:@"AVSampleRateKey"] longValue]);

BPM.inputSamples(sampleBuffer, len/player.numberOfChannels);

NSLog(@"Beats Per Minute = %f", BPM.getBpm());