需要引入lame静态库

#import "lame.h"

- (void)convertPCMToMp3Success:(void(^)(NSString *mp3Path))success
                failure:(void(^)(NSError *error))failure {
    NSString *filePath = [NSHomeDirectory() stringByAppendingString:@"/Documents/mp3.mp3"];
    NSString *mp3FilePath = filePath;
    NSString *LicensePath = [NSString pathWithComponents:@[[[NSBundle mainBundle] bundlePath], @"temp.pcm"]];
    NSString *pcmFilePath = LicensePath;
    @try {
        int read,write;
        // 只读方式打开被转换音频文件
        FILE *pcm = fopen([pcmFilePath cStringUsingEncoding:1], "rb");
        
        if (!pcm) {
            return;
        }
        // 删除头，否则在前一秒钟会有杂音
        fseek(pcm, 4 * 1024, SEEK_CUR);
        // 只写方式打开生成的MP3文件
        FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], "wb");
        
        const int PCM_SIZE = 8192;
        const int MP3_SIZE = 8192;
        short int pcm_buffer[PCM_SIZE * 2];
        unsigned char mp3_buffer[MP3_SIZE];
        
        // 这里要注意，lame的配置要跟AVAudioRecorder的配置一致，否则会造成转换不成功
        lame_t lame = lame_init();
        // 采样率需要和百度语音一致（百度16k，mp3一般是双声道的，设置8k）
        lame_set_in_samplerate(lame, 8000.0);
        
        lame_set_VBR(lame, vbr_default);
        lame_init_params(lame);
        
        do {
            //以二进制形式读取文件中的数据
            read = (int)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);
            }
            
            /*
             * 二进制形式写数据到文件中
             *
             * mp3_buffer：数据输出到文件的缓冲区首地址
             * write：一个数据块的字节数
             * 1：指定一次输出数据块的个数
             * mp3：文件指针
             */
            fwrite(mp3_buffer, write, 1, mp3);
        } while (read != 0);
        
        lame_close(lame);
        fclose(mp3);
        fclose(pcm);
    } @catch (NSException *exception) {
        if (failure) {
            failure(nil);
        }
    } @finally {
        if (success) {
            success(mp3FilePath);
        }
    }
}

lame静态库下载地址
链接: https://pan.baidu.com/s/1BLw5kbmrpXP1RaV5PEuqSg 密码: jnmk