使用第三方 lame ,Mp3音频编码器.   

使用 AVAudioRecorder 进行音频录制之前,进行参数设置:

NSString *recordTemporaryPathString = [NSString stringWithFormat:@"%@/temporary",self.audioTemporarySavePath];
//LinearPCM 是iOS的一种无损编码格式,但是体积较为庞大
//录音设置
NSMutableDictionary *recordSettings = [[NSMutableDictionary alloc] init];
//录音格式 无法使用
[recordSettings setValue :[NSNumber numberWithInt:kAudioFormatLinearPCM] forKey: AVFormatIDKey];
//采样率
[recordSettings setValue :[NSNumber numberWithFloat:11025.0] forKey: AVSampleRateKey];//44100.0
//通道数
[recordSettings setValue :[NSNumber numberWithInt:2] forKey: AVNumberOfChannelsKey];
//线性采样位数
//[recordSettings setValue :[NSNumber numberWithInt:16] forKey: AVLinearPCMBitDepthKey];
//音频质量,采样质量
[recordSettings setValue:[NSNumber numberWithInt:AVAudioQualityMin] forKey:AVEncoderAudioQualityKey];

#include "lame.h"

- (void)audio_PCMtoMP3
{

    NSString *mp3FileName = [self.audioFileSavePath lastPathComponent];
    mp3FileName = [mp3FileName stringByAppendingString:@".mp3"];
    NSString *mp3FilePath = [self.audioTemporarySavePath stringByAppendingPathComponent:mp3FileName];
    
    @try {
        int read, write;
        
        FILE *pcm = fopen([self.audioFileSavePath cStringUsingEncoding:1], "rb");  //source 被转换的音频文件位置
        fseek(pcm, 4*1024, SEEK_CUR);                                   //skip file header
        FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], "wb");  //output 输出生成的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];
        
        lame_t lame = lame_init();
        lame_set_in_samplerate(lame, 11025.0);
        lame_set_VBR(lame, vbr_default);
        lame_init_params(lame);
        
        do {
            read = fread(pcm_buffer, 2*sizeof(short int), 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 {
        self.audioFileSavePath = mp3FilePath;
        NSLog(@"MP3生成成功: %@",self.audioFileSavePath);
    }

}

更多iOS疯狂详解:http://blog.csdn.net/wanglongblog

iOS疯狂详解之录制音频转换成Mp3