如何在objective-c中获得每首歌曲的节拍数

问题描述

我做了很多R& D但没有得到任何好的答案。我正在研究iphone中的音乐类型应用程序，我必须根据每分钟的节拍对歌曲进行分类。所以我的第一个任务是找出歌曲的BPM。我们怎么能这样做？我得到了一些答案：
1.使用MPMediaItem类的MPMediaItemPropertyBeatsPerMinute属性，它会正常工作。我对此有疑问，因为有些人说它会返回null。
您是否有任何示例代码或逻辑来实现此目的。

I did lots of R&D but did not get any good answer. I am working on music type app in iphone and i have to categorized songs on the basis of beats per minute.So my first task to find out BPM of song.How can we do that? I got some answers like:1.using MPMediaItemPropertyBeatsPerMinute property of MPMediaItem class ,will it work fine. I have doubt on this because some guys said it will return null.Do you have any sample code or logic to get this.

提前致谢。

推荐答案

你可以使用用于检测歌曲的BPM。

You can use http://www.un4seen.com/ for detecting BPM of song.

以下是使用此库计算BPM的代码。

Here is code for calculating BPM using this library.

HSTREAM mainStream = BASS_StreamCreateFile(FALSE,[pathStr UTF8String],0,0,BASS_SAMPLE_FLOAT|BASS_STREAM_PRESCAN|BASS_STREAM_DECODE);

float playBackDuration=BASS_ChannelBytes2Seconds(mainStream, BASS_ChannelGetLength(mainStream, BASS_POS_BYTE));

HSTREAM  bpmStream=BASS_StreamCreateFile(FALSE, [pathStr UTF8String], 0, 0, BASS_STREAM_PRESCAN|BASS_SAMPLE_FLOAT|BASS_STREAM_DECODE);

float BpmValue= BASS_FX_BPM_DecodeGet(
                                bpmStream,
                                0.00,
                                playBackDuration,
                                MAKELONG(45,256),
                                BASS_FX_BPM_MULT2,
                                 NULL);


    //Check if BpmValue have any value or not.
    //If it haven't any value then set default value to 128.
    if(BpmValue<=0)
          BpmValue = 128.00;

您可以使用此库进行许多其他操作。

You can do many other things like scratching using this library.

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