自动检测没有声音AVrecorder

Question

我想在录制的同时检测声音。如果声音停止2-3秒，则录音应自动停止。

有什么办法吗？我已经录好了：

NSArray *dirPaths;
        NSString *docsDir;

        dirPaths = NSSearchPathForDirectoriesInDomains(
                                                       NSDocumentDirectory, NSUserDomainMask, YES);
        docsDir = [dirPaths objectAtIndex:0];
        NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
        [dateFormatter setDateFormat:@"ddMMyyyyhh:mm:ss"];

        NSDate *now = [[NSDate alloc] init];
        NSString *dateString = [dateFormatter stringFromDate:now];
        dateString=[NSString stringWithFormat:@"%@.caf",dateString];
        soundFilePath = [docsDir
                                   stringByAppendingPathComponent:dateString];
        NSLog(@"soundFilePath==>%@",soundFilePath);
        NSURL *soundFileURL = [NSURL fileURLWithPath:soundFilePath];
        [soundFilePath retain];
        NSDictionary *recordSettings = [NSDictionary
                                        dictionaryWithObjectsAndKeys:
                                        [NSNumber numberWithInt:AVAudioQualityMin],
                                        AVEncoderAudioQualityKey,
                                        [NSNumber numberWithInt:16],
                                        AVEncoderBitRateKey,
                                        [NSNumber numberWithInt: 2],
                                        AVNumberOfChannelsKey,
                                        [NSNumber numberWithFloat:44100.0],
                                        AVSampleRateKey,
                                        nil];
        NSError *error = nil;
        recorder = [[AVAudioRecorder alloc]
                    initWithURL:soundFileURL
                    settings:recordSettings
                    error:&error];
        if (error)
        {
            NSLog(@"error: %@", [error localizedDescription]);
        } else {
            [recorder prepareToRecord];
        }
        [recorder record];

提前感谢

Answer 1

您应该使用音频级别计量的AVAudioRecorder支持来跟踪音频级别，并在音频级别低于某个阈值时停止录制。要启用计量-

[anAVAudioRecorder setMeteringEnabled:YES];

然后你可以定期调用：

[anAVAudioRecorder updateMeters];
power = [anAVAudioRecorder averagePowerForChannel:0];
if (power > threshold && anAVAudioRecorder.recording==NO)
    [anAVAudioRecorder record];
else if (power < threshold && anAVAudioRecorder.recording==YES)
    [anAVAudioRecorder stop];

阈值:给定音频通道当前平均功率的浮点表示，单位为分贝。返回值为0 dB表示满量程或最大功率；返回值为-160 dB表示最小功率(即接近静默)。

如果提供给音频播放器的信号超过±满刻度，则返回值可能超过0(即可能进入正值范围)。

[apple docs]