iOS SoundTouch 框架 BPM 检测示例

Question

我搜索了整个网络，但找不到有关如何使用SoundTouch library 进行节拍检测的教程。

（注意：在此之前我没有 C++ 经验。我知道 C、Objective-C 和 Java。所以我可能会搞砸一些，但它可以编译。）

我将framework 添加到我的项目中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) 歌曲字节信息让我感到困惑。

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

经过数小时的调试和阅读网络上有限的文档后，我在偶然发现之前修改了一些内容：您需要在 inputSamples() 函数中将 numSamples 除以 numberOfChannels。

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());

Answer 2

我已尝试使用此解决方案从 iOS 音乐库中的 mp3 文件（使用 TSLibraryImport 类转换为 wav）读取 BPM：

                                MPMediaItem *item = [collection representativeItem];

                                 NSURL *urlStr = [item valueForProperty:MPMediaItemPropertyAssetURL];

                                 TSLibraryImport* import = [[TSLibraryImport alloc] init];

                                 NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
                                 NSString *documentsDirectory = [paths objectAtIndex:0];

                                 NSURL* destinationURL = [NSURL fileURLWithPath:[documentsDirectory stringByAppendingPathComponent:@"temp_data"]];
                                 [[NSFileManager defaultManager] removeItemAtURL:destinationURL error:nil];

                                 [import importAsset:urlStr toURL:destinationURL completionBlock:^(TSLibraryImport* import) {

                                     NSString *outPath = [documentsDirectory stringByAppendingPathComponent:@"temp_data"];


                                     NSData *data = [NSData dataWithContentsOfFile:outPath];
                                     AVAudioPlayer *player =[[AVAudioPlayer alloc] initWithData:data error:NULL];

                                     NSUInteger len = [player.data length];
                                     int numChannels = player.numberOfChannels;

                                     soundtouch::SAMPLETYPE sampleBuffer[1024];

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


                                     for (NSUInteger i = 0; i <= len - 1024; i = i + 1024) {

                                         NSRange r = NSMakeRange(i, 1024);
                                         //NSData *temp = [player.data subdataWithRange:r];
                                         [player.data getBytes:sampleBuffer range:r];

                                         int samples = sizeof(sampleBuffer) / numChannels;

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

                                     }

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


                                 }];

奇怪的是计算出来的BMP总是一样的值：

2013-10-02 03:05:36.725 AppTestAudio[1464:1803]  Beats Per Minute = 117.453835

无论是哪个轨道，即帧数或缓冲区大小（这里我使用 2K 缓冲区大小作为库源代码中的 SoundTouch 示例）。

Answer 3

对于 Swift 3：

https://github.com/Luccifer/BPM-Analyser

并像这样使用它：

guard let filePath = Bundle.main.path(forResource: "TestMusic", ofType: "m4a"),
let url = URL(string: filePath) else {return "error occured, check fileURL"}

BPMAnalyzer.core.getBpmFrom(url, completion: nil)

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