下载
1、下载编译脚本：https://github.com/kewlbear/lame-ios-build
2、下载lame：http://lame.sourceforge.net
3、新建文件夹用来存放下载下来的lame和脚本文件
4、在新建的文件夹下运行：./build-lame.sh，运行结果如下图
编译完成后生成fat-lame文件夹，将fat-lame文件夹中的lame.h和libmp3lame.a导入工程即可
使用
将编译完成后的lame库加入到工程中
注意:
1、初始化lame的时候，要设置1为单通道。设置单声道会更大程度减少压缩后文件的体积。
lame_set_num_channels(lame,1); //设置1为单通道，默认为2双通道
2、lame_close(lame);之前需要添加：
lame_mp3_tags_fid(lame, mp3);// 可解决获取时长不准的问题
引入库头文件
//ConvertAudioFile.m
#import "lame.h"
录制完成后转码
//这是录完再转码的方法, 如果录音时间比较长的话,会要等待几秒...
+ (void)conventToMp3WithCafFilePath:(NSString *)cafFilePath
mp3FilePath:(NSString *)mp3FilePath
sampleRate:(int)sampleRate
callback:(void(^)(BOOL result))callback
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
@try {
int read, write;
FILE *pcm = fopen([cafFilePath 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_num_channels(lame,1);//设置1为单通道，默认为2双通道
lame_set_in_samplerate(lame, sampleRate);
lame_set_VBR(lame, vbr_default);
lame_init_params(lame);
do {
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);
}
fwrite(mp3_buffer, write, 1, mp3);
} while (read != 0);
lame_mp3_tags_fid(lame, mp3);
lame_close(lame);
fclose(mp3);
fclose(pcm);
}
@catch (NSException *exception) {
NSLog(@"%@",[exception description]);
if (callback) {
callback(NO);
}
}
@finally {
NSLog(@"-----\n MP3生成成功: %@ ----- \n", mp3FilePath);
if (callback) {
callback(YES);
}
}
});
调用
[ConvertAudioFile conventToMp3WithCafFilePath:self.cafPathmp3FilePath:self.mp3Path
{
sampleRate:ETRECORD_RATE callback:^(BOOL result)
NSLog(@"---- 转码完成 --- result %d ---- ", result);}];
边录制边转码
通常我们是在录制结束之后, 再进行转码; 当录制的时间较长 , 会消耗的时间比较长，用户需要等待转码结束后,才能操作; 但是如果我们使用边录制，边转码的方式, 开另外开个线程同时进行转码,则几乎没有等待的时间。
具体实现方法：当录音进行中时, 会持续读取到指定大小文件来进行编码，读取不到，则线程休眠在while的条件中, 我们收到录音结束的条件，则会结束do while的循环。我们需要在录制结束后发送个信号, 让 do while跳出循环。
- (void)conventToMp3WithCafFilePath:(NSString *)cafFilePath
mp3FilePath:(NSString *)mp3FilePath
sampleRate:(int)sampleRate
callback:(void(^)(BOOL result))callback
{
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
@try {
int read, write;
FILE *pcm = fopen([cafFilePath cStringUsingEncoding:1], "rb"); //source 被转换的音频文件位置
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];
//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();
lame_set_num_channels(lame,1);//设置1为单通道，默认为2双通道 设置单声道会更大程度减少压缩后文件的体积
lame_set_in_samplerate(lame, sampleRate);//采样率
lame_set_VBR(lame, vbr_default);
lame_init_params(lame);
BOOL isSkipPCMHeader = NO;
__weak typeof(self) weakSelf = self;
do {
long curpos = ftell(pcm);
long startPos = ftell(pcm);
fseek(pcm, 0, SEEK_END);
long endPos = ftell(pcm);
long length = endPos - startPos;
fseek(pcm, curpos, SEEK_SET);
if (length > PCM_SIZE * 2 * sizeof(short int)) {
if (!isSkipPCMHeader) {
//Uump audio file header, If you do not skip file header
//you will heard some noise at the beginning!!!
fseek(pcm, 4 * 1024, SEEK_CUR);
isSkipPCMHeader = YES;
NSLog(@"skip pcm file header !!!!!!!!!!");
}
read = (int)fread(pcm_buffer, 2 * sizeof(short int), PCM_SIZE, pcm);
write = lame_encode_buffer_interleaved(lame, pcm_buffer, read, mp3_buffer,
MP3_SIZE);
fwrite(mp3_buffer, write, 1, mp3);
NSLog(@"read %d bytes", write);}
else {
[NSThread sleepForTimeInterval:0.05];
// MyLog(@"sleep");
}
} while (! weakSelf.stopRecord);
lame_mp3_tags_fid(lame, mp3);// 解决获取时长不准的问题
lame_close(lame);
fclose(mp3);
fclose(pcm);
}
@catch (NSException *exception) {
MyLog(@"%@",[exception description]);
if (callback) {
callback(NO);
}
}
@finally {
MyLog(@"-----\n MP3生成成功: %@ ----- \n", mp3FilePath);
if (callback) {
callback(YES);
}
}
});
}
调用
[[ConvertAudioFile sharedInstance] conventToMp3WithCafFilePath:self.cafPathmp3FilePath:self.mp3Path
sampleRate:ETRECORD_RATE callback:^(BOOL result)
{
NSLog(@"---- 转码完成 --- result %d ---- ", result);
}];
参考：
https://blog.csdn.net/u011270282/article/details/77483359
https://blog.csdn.net/lovechris00/article/details/79034036
https://blog.csdn.net/ysy441088327/article/details/7392842
https://blog.csdn.net/lovechris00/article/details/52033555