Lame: converts ios recordings to mp3 formats.

Recording is performed on ios devices. The format of the recording file is caf. However, this format cannot be played on many devices. To adapt to the playback function of the terminal, caf is converted to an mp3 file.

When recording a caf file, you must use a dual channel. Otherwise, the audio is incorrect when the file is converted to MP3 format. Set the caf recording end:

 

NSMutableDictionary * recordSetting = [NSMutableDictionary dictionary];

 

[RecordSetting setValue: [NSNumber numberWithInt: kAudioFormatLinearPCM] forKey: AVFormatIDKey]; //

[RecordSetting setValue: [NSNumber numberWithFloat: 8000.0] forKey: AVSampleRateKey]; // Sampling Rate

[RecordSetting setValue: [NSNumber numberWithInt: 2] forKey: AVNumberOfChannelsKey]; // sound channel, which must be a two-channel

[RecordSetting setValue: [NSNumber numberWithInt: AVAudioQualityLow] forKey: AVEncoderAudioQualityKey]; // audio quality

The code for converting mp3 files is:

 

NSString * cafFilePath = cafFilePathName; // caf file path

NSString * mp3FilePath = mp3FilePathName; // path for storing mp3 files

NSFileManager * fileManager = [NSFileManager defaultManager];

If ([fileManager removeItemAtPath: mp3FilePath error: nil])

{

NSLog (@ "delete ");

}

@ Try {

Int read, write;

FILE * pcm = fopen ([cafFilePath cStringUsingEncoding: 1], "rb"); // location of the audio FILE to which the source is converted

If (pcm = NULL)

{

NSLog (@ "file not found ");

}

Else

{

Fseek (pcm, 4*1024, SEEK_CUR); // skip file header

FILE * mp3 = fopen ([mp3FilePath cStringUsingEncoding: 1], "wb"); // output the location of the generated Mp3 FILE

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); // you can specify 1 as a single channel. The default value is 2.

Lame_set_in_samplerate (lame, 8000.0); // 11025.0

// Lame_set_VBR (lame, vbr_default );

Lame_set_brate (lame, 8 );

Lame_set_mode (lame, 3 );

Lame_set_quality (lame, 2);/* 2 = high 5 = medium 7 = low sound quality */

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 );

Return YES;

}

Return NO;

}

@ Catch (NSException * exception ){

NSLog (@ "% @", [exception description]);

Return NO;

}

@ Finally {

NSLog (@ "execution completed ");

}