iOS音频开发(录音+播放+剪辑+合成+压缩转码)

录音:

//音频会话
AVAudioSession *session = [AVAudioSession sharedInstance];
NSError *sessionError;
/*
AVAudioSessionCategoryPlayAndRecord :录制和播放
AVAudioSessionCategoryAmbient       :用于非以语音为主的应用,随着静音键和屏幕关闭而静音.
AVAudioSessionCategorySoloAmbient   :类似AVAudioSessionCategoryAmbient不同之处在于它会中止其它应用播放声音。
AVAudioSessionCategoryPlayback      :用于以语音为主的应用,不会随着静音键和屏幕关闭而静音.可在后台播放声音
AVAudioSessionCategoryRecord        :用于需要录音的应用,除了来电铃声,闹钟或日历提醒之外的其它系统声音都不会被播放,只提供单纯录音功能.
*/
[session setCategory:AVAudioSessionCategoryPlayAndRecord error:&sessionError];
[session setActive:YES error:nil];
// 录音参数
NSDictionary *setting = [NSDictionary dictionaryWithObjectsAndKeys:
                               [NSNumber numberWithInt:kAudioFormatLinearPCM], AVFormatIDKey,// 编码格式
                               [NSNumber numberWithFloat:8000], AVSampleRateKey, //采样率
                               [NSNumber numberWithInt:2], AVNumberOfChannelsKey, //通道数
                               [NSNumber numberWithInt:16], AVLinearPCMBitDepthKey,  //采样位数(PCM专属)
                               [NSNumber numberWithBool:NO], AVLinearPCMIsNonInterleaved,  //是否允许音频交叉(PCM专属)
                               [NSNumber numberWithBool:NO],AVLinearPCMIsFloatKey,  //采样信号是否是浮点数(PCM专属)
                               [NSNumber numberWithBool:NO], AVLinearPCMIsBigEndianKey,  //是否是大端存储模式(PCM专属)
                               [NSNumber numberWithInt:AVAudioQualityMax], AVEncoderAudioQualityKey,  //音质
                               nil];
self.audioRecorder.delegate = self;
//开启音频测量
self.audioRecorder.meteringEnabled = YES;
//保存路径
self.audioRecorder = [[AVAudioRecorder alloc] initWithURL:[NSURL URLWithString:filePath] settings:setting error:nil];
//准备 / 开始录音
[self.audioRecorder prepareToRecord];
[self.audioRecorder record];

//暂停录音
[self.audioRecorder pause];
//停止录音
[self.audioRecorder stop];
//删除录音

//AVAudioRecorderDelegate
//when a recording has been finished or stopped. This method is NOT called if the recorder is stopped due to an interruption.(录音完成)
- (void)audioRecorderDidFinishRecording:(AVAudioRecorder *)recorder successfully:(BOOL)flag;
//if an error occurs while encoding it will be reported to the delegate(编码发生错误)
- (void)audioRecorderEncodeErrorDidOccur:(AVAudioRecorder *)recorder error:(NSError * __nullable)error;
//when the audio session has been interrupted while the recorder was recording. The recorded file will be closed.(被打断)
- (void)audioRecorderBeginInterruption:(AVAudioRecorder *)recorder NS_DEPRECATED_IOS(2_2, 8_0);
//when the audio session interruption has ended and this recorder had been interrupted while recording(被打断结束)
- (void)audioRecorderEndInterruption:(AVAudioRecorder *)recorder withOptions:(NSUInteger)flags NS_DEPRECATED_IOS(6_0, 8_0);

播放

AVAudioSession *session = [AVAudioSession sharedInstance];
NSError *sessionError;
[session setCategory:AVAudioSessionCategoryPlayback error:&sessionError];
[session setActive:YES error:nil];

//开启接近监视(靠近耳朵的时候听筒播放,离开的时候扬声器播放)
[[UIDevice currentDevice] setProximityMonitoringEnabled:YES];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sensorStateChange:)name:UIDeviceProximityStateDidChangeNotification object:nil];

self.audioPlayer = [[AVAudioPlayer alloc] initWithContentsOfURL:[NSURL URLWithString:filePath] error:nil];

self.audioPlayer.delegate = self;
//准备播放 / 播放
[self.audioPlayer prepareToPlay];
[self.audioPlayer play];

//停止播放
[self.audioPlayer stop];
//暂停播放
[self.audioPlayer pause];

//proximityStateChange:(NSNotificationCenter *)notification方法
if ([[UIDevice currentDevice] proximityState] == YES) {
    //靠近耳朵
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord error:nil];
} else {
    //离开耳朵
    [[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayback error:nil];
}

//AVAudioPlayerDelegate
//when a sound has finished playing. This method is NOT called if the player is stopped due to an interruption(播放完成)
- (void)audioPlayerDidFinishPlaying:(AVAudioPlayer *)player successfully:(BOOL)flag;
//if an error occurs while decoding it will be reported to the delegate.(解码结束)
- (void)audioPlayerDecodeErrorDidOccur:(AVAudioPlayer *)player error:(NSError * __nullable)error;
//when the audio session has been interrupted while the player was playing. The player will have been paused(被打断)
- (void)audioPlayerBeginInterruption:(AVAudioPlayer *)player NS_DEPRECATED_IOS(2_2, 8_0);
//when the audio session interruption has ended and this player had been interrupted while playing(被打断结束)
- (void)audioPlayerEndInterruption:(AVAudioPlayer *)player withOptions:(NSUInteger)flags NS_DEPRECATED_IOS(6_0, 8_0);

剪辑

将路径filePath下的音频文件从time截取到time2后在resultPath中输出

//AVURLAsset是AVAsset的子类,AVAsset类专门用于获取多媒体的相关信息,包括获取多媒体的画面、声音等信息.而AVURLAsset子类的作用则是根据NSURL来初始化AVAsset对象.
AVURLAsset *videoAsset = [AVURLAsset assetWithURL:[NSURL fileURLWithPath:filePath]];
//音频输出会话
//AVAssetExportPresetAppleM4A: This export option will produce an audio-only .m4a file with appropriate iTunes gapless playback data(输出音频,并且是.m4a格式)
AVAssetExportSession *exportSession = [AVAssetExportSession exportSessionWithAsset:videoAsset presetName:AVAssetExportPresetAppleM4A];
//设置输出路径 / 文件类型 / 截取时间段
exportSession.outputURL = [NSURL fileURLWithPath:resultPath];
exportSession.outputFileType = AVFileTypeAppleM4A;
exportSession.timeRange = CMTimeRangeFromTimeToTime(CMTimeMake(time1, 1), CMTimeMake(time2, 1));
[exportSession exportAsynchronouslyWithCompletionHandler:^{
    //exporeSession.status
}];

合成

将路径filePath1和路径filePath2下的音频合成

//AVURLAsset子类的作用则是根据NSURL来初始化AVAsset对象.
AVURLAsset *videoAsset1 = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:filePath1] options:nil];
AVURLAsset *videoAsset2 = [[AVURLAsset alloc] initWithURL:[NSURL fileURLWithPath:filePath2] options:nil];
//音频轨迹(一般视频至少有2个轨道,一个播放声音,一个播放画面.音频有一个)
AVAssetTrack *assetTrack1 = [[videoAsset1 tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
AVAssetTrack *assetTrack2 = [[videoAsset2 tracksWithMediaType:AVMediaTypeAudio] objectAtIndex:0];
//AVMutableComposition用来合成视频或音频
AVMutableComposition *composition = [AVMutableComposition composition];
AVMutableCompositionTrack *compositionTrack = [composition addMutableTrackWithMediaType:AVMediaTypeAudio preferredTrackID:kCMPersistentTrackID_Invalid];
// 把第二段录音添加到第一段后面
[compositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset1.duration) ofTrack:assetTrack1 atTime:kCMTimeZero error:nil];
[compositionTrack insertTimeRange:CMTimeRangeMake(kCMTimeZero, videoAsset2.duration) ofTrack:assetTrack2 atTime:videoAsset1.duration error:nil];
//输出
AVAssetExportSession *exporeSession = [AVAssetExportSession exportSessionWithAsset:composition presetName:AVAssetExportPresetAppleM4A];
exporeSession.outputFileType = AVFileTypeAppleM4A;
exporeSession.outputURL = [NSURL fileURLWithPath:resultPath];
[exporeSession exportAsynchronouslyWithCompletionHandler:^{
    //exporeSession.status
}];

压缩转码

下载LAME (Lame Aint an MP3 Encoder)

双击解压后放到一个文件夹下,文件夹需要命名为lame,否则无法生成.h和.a文件

使用Terminal进入该文件夹,编译生成静态库,脚本代码

$:cd cd /Users/mac/Desktop/lame
//创建build_lame.sh
$:touch build_lame.sh
//打开build_lame.sh,粘贴脚本代码
$:open build_lame.sh
//编译执行脚本,生成静态库,需要输入本机密码
$:sudo sh build_lame.sh

将fat-lame文件夹下的include文件夹和lib文件夹放入工程,再写一个OC的类调用lame.h

@try {
    int read, write;
    FILE *pcm = fopen([filePath cStringUsingEncoding:1], "rb");//被转换的音频文件位置
    fseek(pcm, 4*1024, SEEK_CUR);
    FILE *mp3 = fopen([resultPath cStringUsingEncoding:1], "wb");//生成的Mp3文件位置

    const int PCM_SIZE = 8192;
    const int MP3_SIZE = 8192;
    short int pcm_buffer[PCM_SIZE*2];
    unsigned char mp3_buffer[MP3_SIZE];

    // 初始化lame编码器
    lame_t lame = lame_init();
    // 设置lame mp3编码的采样率 / 声道数 / 比特率
    lame_set_in_samplerate(lame, 8000);
    lame_set_num_channels(lame,2);
    lame_set_out_samplerate(lame, 8000);
    lame_set_brate(lame, 8);
    // MP3音频质量.0~9.其中0是最好,非常慢,9是最差.
    lame_set_quality(lame, 7);

    // 设置mp3的编码方式
    lame_set_VBR(lame, vbr_default);
    lame_init_params(lame);

    do {
        size_t size = (size_t)(2 * sizeof(short int));
        read = fread(pcm_buffer, size, PCM_SIZE, pcm);
        if (read == 0) {
            write = lame_encode_flush(lame, mp3_buffer, MP3_SIZE);
        } else {
            write = lame_encode_buffer_interleaved(lame, pcm_buffer, read, mp3_buffer, MP3_SIZE);
        }
        fwrite(mp3_buffer, write, 1, mp3);

    } while (read != 0);

    lame_close(lame);
    fclose(mp3);
    fclose(pcm);
}
@catch (NSException *exception) {
    NSLog(@"%@",[exception description]);
}
@finally {
    // 转码完成
    return resultPath;
}

基本上可以将100K左右的录音文件压缩到10K以下

参考1 参考2 参考3 参考4