我需要更改mp3比特率，我在Windows和Linux下使用lame for cpp项目。我想我需要将mp3转换为wav，然后将wav转换为具有所需比特率的mp3。
对于wav到mp3，我已经有了代码（使用跛脚）它的工作原理 对于mp3到wav，应用程序在hip_decode上崩溃存在问题 可能是由于文件开头的ID3标签造成的 如何跳过ID3标签或这是一个不同的问题？
这是我使用
的代码bool Helper::convert2Wav(QString fromFile, QString toFile) {
int read, write;
int ctn = 0;
FILE *mp3_in =fopen(fromFile.toLocal8Bit().data(),"rb");
//this should be WAV
FILE *pcm_out =fopen(toFile.toLocal8Bit().data(),"wb");
const int PCM_SIZE = 4096;
const int MP3_SIZE = 4096;
short int pcm_buffer[PCM_SIZE*2];
short int pcm_buffer1[PCM_SIZE];
short int pcm_buffer2[PCM_SIZE];
unsigned char mp3_buffer[MP3_SIZE];
memset(pcm_buffer, 0, sizeof(pcm_buffer));
memset(pcm_buffer1, 0, sizeof(pcm_buffer1));
memset(pcm_buffer2, 0, sizeof(pcm_buffer2));
memset(mp3_buffer, 0, sizeof(mp3_buffer));
lame_t lame = lame_init();
hip_t l = hip_decode_init();
lame_set_in_samplerate(lame, 44100);
//lame_set_VBR(lame, vbr_default);
//lame_set_mode(lame, MONO);
lame_init_params(lame);
qDebug()<<"start decoding";
do {
ctn += 4096;
qDebug()<<"a message:"<<ctn;
read = fread(mp3_buffer, sizeof(unsigned char), MP3_SIZE, mp3_in);
hip_decode(l, mp3_buffer, MP3_SIZE, pcm_buffer1, pcm_buffer2);
//read = hip_decode(l, mp3_buffer, MP3_SIZE, pcm_buffer1,pcm_buffer2);
//memcpy(pcm_buffer, pcm_buffer1, sizeof(pcm_buffer1));
//memcpy(&pcm_buffer[PCM_SIZE], pcm_buffer2, sizeof(pcm_buffer2));
//write = lame_encode_buffer_interleaved(lame, pcm_buffer, read,mp3_buffer, MP3_SIZE);
//fwrite(pcm_buffer, 1, sizeof(pcm_buffer), pcm_out);
} while (read != 0);
hip_decode_exit(l);
lame_close(lame);
fclose(pcm_out);
fclose(mp3_in);
return true;
}
输出崩溃：
start decoding
a message: 4096
a message: 8192
a message: 12288
1 ?? 0x7ffff7b8f0b5
2 hip_decode1_headers 0x7ffff7b8f34b
3 hip_decode1_headers 0x7ffff7b8f385
4 hip_decode_headers 0x7ffff7b8f42d
5 hip_decode 0x7ffff7b8f47c
6 Helper::convert2Wav helper.cpp 498 0x5555555b0fe7
7 ?? 0x4490551063006a0
MP3_SIZE 258346945 int
PCM_SIZE 234884892 int
ctn 189860957 int
l 1050198802094820962 hip_t
lame 1165886731226582744 lame_t
mp3_buffer "\005\0029lM^J\035�xo�R����(����Rj\172175r�V�����ԡCb٥���0a�ע�r�4�A��7Xj�Q0u�\033Os��L5�S$D2\002\016� UxCp\014s��08\004+7��@"�r"... (4096) unsigned char[4096]
mp3_in 0xe0b0e1e0e060d4a FILE*
pcm_buffer @0x7fffffff89a0 short[8192]
pcm_buffer1 @0x7fffffff69a0 short[4096]
pcm_buffer2 @0x7fffffff49a0 short[4096]
pcm_out 0xc460bb00bb40c82 FILE*
read 229772669 int
write <optimized out>
似乎这不是ID3问题，我使用此代码https://searchcode.com/file/31230698/ID3.cpp来读取ID3，它显示没有ID3标签 但仍然在同一点崩溃：
Has ID3v2 Tag: No
Tag size: 0
start decoding skip tag_size: 0
a message: 4096
a message: 8192
a message: 12288
答案 0 :(得分：0)
回答我的蹩脚问题：
bool Helper::changeMp3Bitrate(QString fromFile, QString toFile, int sample_rate, int channels) {
qDebug()<<"Helper::changeMp3Bitrate channels:"<<channels<<" sample_rate:"<<sample_rate;
int read;
int ctn = 0;
int tag_size=0;
ID3 tag(fromFile.toLocal8Bit().data());
if(tag.hasTag()) {
qDebug()<<"Helper::changeMp3Bitrate mp3 has tags";
tag.parse();
}
else
qDebug()<<"Helper::changeMp3Bitrate mp3 no tags";
qDebug()<<"Helper::changeMp3Bitrate tagSize:"<< tag.size();
if(tag.hasTag()) {
tag_size=tag.size();
qDebug()<<"Helper::changeMp3Bitrate tagSize:"<< tag.size();
}
FILE *mp3_in =fopen(fromFile.toLocal8Bit().data(),"rb");
FILE *mp3_out =fopen(toFile.toLocal8Bit().data(),"wb");
const int PCM_SIZE = 4096;
const int MP3_SIZE = 4096;
short int pcm_buffer[PCM_SIZE*100*2];
short int pcm_buffer1[PCM_SIZE*100];
short int pcm_buffer2[PCM_SIZE*100];
unsigned char mp3_buffer[MP3_SIZE];
unsigned char mp3_out_buffer[PCM_SIZE*100];
memset(pcm_buffer, 0, sizeof(pcm_buffer));
memset(pcm_buffer1, 0, sizeof(pcm_buffer1));
memset(pcm_buffer2, 0, sizeof(pcm_buffer2));
memset(mp3_buffer, 0, sizeof(mp3_buffer));
memset(mp3_out_buffer, 0, sizeof(mp3_out_buffer));
lame_t lame = lame_init();
hip_t l = hip_decode_init();
lame_set_in_samplerate(lame, sample_rate);
lame_set_mode(lame, STEREO);
lame_set_brate(lame,Zm().defaultBitrate);
lame_set_num_channels(lame, channels);
lame_init_params(lame);
if(tag_size) {
qDebug()<<"Helper::changeMp3Bitrate skip tag_size bytes:"<<tag_size;
fread(NULL,sizeof(unsigned char), tag_size, mp3_in);
}
qDebug()<<"Helper::changeMp3Bitrate decoding";
do {
read = fread(mp3_buffer, sizeof(unsigned char), MP3_SIZE, mp3_in);
int numdec=hip_decode(l, mp3_buffer, MP3_SIZE, pcm_buffer1, pcm_buffer2);
ctn += read;
qDebug()<<"Helper::changeMp3Bitrate mp3 read:"<<ctn;
if(numdec>0) {
qDebug()<<"Helper::changeMp3Bitrate mp3 numdec:"<<numdec;
memcpy(pcm_buffer, pcm_buffer1, numdec);
memcpy(&pcm_buffer[numdec], pcm_buffer2, numdec);
int write = lame_encode_buffer(lame, pcm_buffer1,pcm_buffer2,numdec, mp3_out_buffer, sizeof(mp3_out_buffer));
qDebug()<<"Helper::changeMp3Bitrate mp3 write to mp3_out:"<<write;
fwrite(mp3_out_buffer, write, 1, mp3_out);
memset(pcm_buffer, 0, sizeof(pcm_buffer));
memset(pcm_buffer1, 0, sizeof(pcm_buffer1));
memset(pcm_buffer2, 0, sizeof(pcm_buffer2));
memset(mp3_buffer, 0, sizeof(mp3_buffer));
memset(mp3_out_buffer, 0, sizeof(mp3_out_buffer));
}
} while (read != 0);
hip_decode_exit(l);
lame_close(lame);
fclose(mp3_in);
fclose(mp3_out);
qDebug()<<"Helper::changeMp3Bitrate finished";
return true;
}