iPhone：用于编辑的音频文件的NSData表示 [英] iPhone: NSData representation of Audio file for Editing

问题描述

我很久以前一直在摸不着头脑，但没有绕过这个。我还没有找到一个音频编辑的例子！我想在原始音频文件中的某个地方插入新的音频文件，将其保存为新转换的音频文件。

I have been scratching my head since long now but not getting around to this. I haven't found a single example for Audio editing! I want to insert new Audio file in between somewhere in original Audio file, save it as new converted audio files.

为此，我编写了以下代码。我从这里。

For this I have written following code. I got this idea from here.

NSString *file1 = [[NSBundle mainBundle] pathForResource:@"file1" ofType:@"caf"]; // Using PCM format
NSString *file2 = [[NSBundle mainBundle] pathForResource:@"file2" ofType:@"caf"];

NSData *file1Data = [[NSData alloc] initWithContentsOfFile:file1];
NSData *file2Data = [[NSData alloc] initWithContentsOfFile:file2];

NSMutableData *mergedData =[[NSMutableData alloc] initWithCapacity:([file1Data length] + [file2Data length])];

// First chunk from original sound file 
NSRange firstChunk;
firstChunk.length = startingPosition;
firstChunk.location = 0;
[mergedData appendData:[file1Data subdataWithRange:firstChunk]];

// Add new sound
[mergedData appendData:file2Data];

// First chunk from original sound file 
NSRange secondChunk;
secondChunk.length = [file1Data length] - startingPosition;
secondChunk.location = startingPosition;
[mergedData appendData:[file1Data subdataWithRange:secondChunk]];

NSLog(@"File1: %d, File2: %d, Merged: %d", [file2Data length], [file2Data length],   [mergedData length]);

// Convert mergedData to Audio file
[mergedData writeToFile:[self filePath:@"converted.caf"] atomically:YES];

[file1Data release];
[file2Data release];
[mergedData release];

使用以下代码播放转换后的声音文件：

Using following code to play converted sound file:

AVAudioPlayer *audioPlayer = [[AVAudioPlayer alloc] 
                          initWithContentsOfURL:[NSURL URLWithString:[self filePath:@"converted.caf"]]  error:nil];
[audioPlayer prepareToPlay];
[audioPlayerr play];

转换的文件无法播放。进一步研究这个我发现将声音转换为NSData截断声音页眉/页脚。是对的吗？请有人帮我解决这个问题。

The converted file doesn't play. Further researching on this I found that converting sound to NSData truncates sound header/footer. Is that right? Could anyone please help me to get this sorted out please.

谢谢。

推荐答案

我认为最好的办法是使用ExtAudioFileRef将每个文件的音频样本提取到缓冲区中。

I think your best bet would be to use an ExtAudioFileRef to extract the audio samples of each file into buffers.

然后你可以自由地将样本混合到一起从你喜欢的任何位置，使用ExtAudioFileWriteAsync将新的混合文件保存到磁盘。

Then you can freely mix the samples together to and from whatever position you like and save the new mixed file to disk using ExtAudioFileWriteAsync.

例如：
将声音1提取到缓冲区A.
将声音2提取到缓冲区B中。

For example: Extract sound 1 into buffer A. Extract sound 2 into buffer B.

创建缓冲区C，其大小为A的长度加上B的长度。
然后使用ExtAudioFileWriteAsync以任何格式将该缓冲区写入磁盘。

Create buffer C whose size is A's length plus B's length. Then write that buffer to disk in whatever format you want using ExtAudioFileWriteAsync.

该文件应该可由AVAudioPlayer播放。

That file should then be playable by AVAudioPlayer.

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