Lame - increase bitrate to 320 - ios

Question

First I want to show my method for converting source .wav files to .mp3 by Lame library:
- (void)convertFromWav:(NSString *)sourceFilePath ToMp3:(NSString *)resultName {
NSString *mp3FileName = [resultName stringByAppendingString:#".mp3"];
NSString *mp3FilePath = [NSTemporaryDirectory() stringByAppendingPathComponent:mp3FileName];
#try {
int read, write;
FILE *pcm = fopen([sourceFilePath UTF8String], "rb"); //source
if (pcm == NULL) {
perror("fopen");
return;
}
fseek(pcm, 4*1024, SEEK_CUR); //skip file header
FILE *mp3 = fopen([mp3FilePath cStringUsingEncoding:1], "wb"); //output
const int sampleRate = 44100;
const int bitsPerSample = 16;
const int numberOfChannels = 2;
const int PCM_SIZE = 8192*2;
const int MP3_SIZE = 8192*2;
short int pcm_buffer[PCM_SIZE*2];
unsigned char mp3_buffer[MP3_SIZE];
lame_t lame = lame_init();
lame_set_in_samplerate(lame, sampleRate);
lame_set_VBR(lame, vbr_default);
lame_init_params(lame);
lame_get_num_samples(lame);
long long fileSize = [[[[NSFileManager defaultManager] attributesOfItemAtPath:sourceFilePath error:nil] objectForKey:NSFileSize] longLongValue];
long duration = fileSize / (sampleRate * numberOfChannels * bitsPerSample / 8);//(fileSize * 8.0f) / (sampleRate * 2);
lame_set_num_samples(lame, (duration * sampleRate));
lame_get_num_samples(lame);
float percent = 0.0;
int totalframes = lame_get_totalframes(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);
int frameNum = lame_get_frameNum(lame);
if (frameNum < totalframes)
percent = (100. * frameNum / totalframes + 0.5);
else
percent = 100;
if ([_delegate respondsToSelector:#selector(convertingProgressChangedWithPercent:)])
{
[_delegate convertingProgressChangedWithPercent:percent];
}
} while (read != 0);
lame_close(lame);
fclose(mp3);
fclose(pcm);
}
#catch (NSException *exception) {
NSLog(#"%#",[exception description]);
}
#finally {
if ([_delegate respondsToSelector:#selector(convertingDidFinish:)])
{
[_delegate convertingDidFinish:mp3FilePath];
}
}
}
It's okay and it's working. As a result I have .mp3 which has 152000 bits per second. But I want to make it 320000 bits per second. How can I change it? I am not good in theory about this stuff so I don't know which values change to what. Thanks.

Answer 1

You want to use lame_set_VBR (lame_t, vbr_off); and then you can use lame_set_brate where you can set the required bitrate amount. Using vbr_off gives you CBR mode as confirmed in the docs (see headers.h) :
*********************************************************************
VBR control
************************************************************************ /* Types of VBR. default = vbr_off = CBR */ int CDECL
lame_set_VBR(lame_global_flags *, vbr_mode); vbr_mode CDECL
lame_get_VBR(const lame_global_flags *);
Try this :
//# for constants of settings
const int sampleRate = 44100;
const int bitsPerSample = 16;
const int numberOfChannels = 2;
const int myBitRate = 320;
//# for Lame settings
lame_t lame = lame_init();
lame_set_in_samplerate (lame_t, sampleRate); //is 44100
lame_set_VBR (lame_t, vbr_off); //force CBR mode
lame_set_brate (lame_t, myBitRate); //is 320
lame_init_params (lame_t);
Also you can probably setup Lame like this :
lame_t lame = lame_init(); instead becomes like this : lame_t = lame_init();
Just saying that if you defined a lame_t I would expect it to require that name for rest of settings. You know like lame_init_params (lame_t); etc.