iOS:录音文件格式

Question

我正在实施录音.它与caf&wave格式工作正常.但问题是文件太大.

那么,任何人都可以帮助我录制音频,其格式也会在窗口和文件大小上播放.

我试过的代码如下:

 dirPaths = NSSearchPathForDirectoriesInDomains(
                                                    NSDocumentDirectory, NSUserDomainMask, YES);
    docsDir = [dirPaths objectAtIndex:0];
     NSString *soundFilePath = [docsDir
                                stringByAppendingPathComponent:@"sound.wave"];
     NSLog(@"%@",soundFilePath);
     NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath];

     NSDictionary *recordSettings = [NSDictionary 
                         dictionaryWithObjectsAndKeys:
                                    [NSNumber numberWithInt:AVAudioQualityMin],
                                     AVEncoderAudioQualityKey,
                                     [NSNumber numberWithInt:16], 
                                     AVEncoderBitRateKey,
                                     [NSNumber numberWithInt: 2], 
                                     AVNumberOfChannelsKey,
                                     [NSNumber numberWithFloat:8000.0], AVSampleRateKey,
                                     [NSNumber numberWithInt:8], AVLinearPCMBitDepthKey,
                                     nil];

     NSError *error = nil;

     audioRecorder = [[AVAudioRecorder alloc]
                      initWithURL:soundFileURL
                      settings:recordSettings
                      error:&error];

     if (error)
     {
         NSLog(@"error: %@", [error localizedDescription]);

     } else {
        [audioRecorder prepareToRecord];
     }

Answer 1

我还尝试使用AVAudioRecorder以AAC编码格式录制音频,最好是.m4a文件.我很快就能够将代码记录到核心音频文件(.caf)中的AAC,但我无法让AVAudioRecorder正确格式化.m4a.我正准备使用较低级别的Audio Units API在我的应用程序中重写录制代码,但我将其放在后面,并添加到代码中以处理共享音频会话.一旦设置完毕,我就回去尝试保存为.m4a并且它刚刚起作用.

这是一些示例代码:

NSArray *dirPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *docsDir = [dirPaths objectAtIndex:0];
NSURL *tmpFileUrl = [NSURL fileURLWithPath:[docsDir stringByAppendingPathComponent:@"tmp.m4a"]];
NSDictionary *recordSettings = [NSDictionary dictionaryWithObjectsAndKeys:
                        [NSNumber numberWithInt: kAudioFormatMPEG4AAC], AVFormatIDKey,
                        [NSNumber numberWithFloat:16000.0], AVSampleRateKey,
                        [NSNumber numberWithInt: 1], AVNumberOfChannelsKey,
                        nil];
NSError *error = nil;
AVAudioRecorder *recorder = [[AVAudioRecorder alloc] initWithURL:tmpFileUrl settings:recordSettings error:&error];
[recorder prepareToRecord];

AVAudioSession *session = [AVAudioSession sharedInstance];
[session setCategory:AVAudioSessionCategoryRecord error:nil];
[session setActive:YES error:nil];

[recorder record];

然后结束我使用的录音:

[recorder stop];
AVAudioSession *session = [AVAudioSession sharedInstance];
int flags = AVAudioSessionSetActiveFlags_NotifyOthersOnDeactivation;
[session setActive:NO withFlags:flags error:nil];

然后可以随意使用'tmpFileUrl'中的文件.

Answer 2

以下是我对高质量和小文件大小(余额)的设置:

NSDictionary *recordSettings = @{AVEncoderAudioQualityKey: @(AVAudioQualityMedium),
                                 AVFormatIDKey: @(kAudioFormatMPEG4AAC),
                                 AVEncoderBitRateKey: @(128000),
                                 AVNumberOfChannelsKey: @(1),
                                 AVSampleRateKey: @(44100)};

这使您接近CD质量的单声道AAC音轨.您应该使用.m4a附加文件,以便在任何地方都可读.所有其他参数都设置为设备默认值,这是您希望在大多数情况下发生的事情.