Data CD's & Audio CD's
A CD-ROM disc is divided into sectors of 2352 bytes. Data CDs use 2048 of these bytes to store the data file. The other bytes are start/stop and sector number information. This method makes it easy for a computer's CD-ROM device to find the right sector.
On the other hand, an audio CD uses all of the 2352 bytes to store audio information and all the bytes are placed in one long sequence. This method makes it hard for the CD-ROM drive to find exactly where the track starts. When the CD-ROM drive starts reading, it usually has no problem delivering the right data, but most CD-ROM drives have problems with starting on the correct byte (sample).
A frame on an audio CD (called a sector on data CDs) is 2352 bytes. There are 75 frames per second which yields 2352 x 75 bytes per second of music. (This can also be calculated by 2 (stereo) x 2 (16 bits) x 44100 Hz per second.) Philips "Red Book" standard specifies that a CD player should be able to position its head on the right frame, but does not indicate where on the frame.
Since a computer program has to read a little piece of the track, write it to the hard disk, read another piece etc., problems may arise. MP3Producer solves this problem by reading a little bit more data than it is written and then compares the end of the previous reading with the beginning of the present reading. As a result, MP3Producer synchronizes the reads. This is called overlapping, synchronization, or jitter correction.
You can select how many overlapping audio frames should be read in every chunk. MP3Producer does not always get enough memory for all the frames it wants, which means that it sometimes has to use a smaller audio buffer. (Under MSCDEX, MP3Producer uses the low DOS memory to buffer data from the CD-ROM drive. Depending on what other device drivers and programs are using memory from that area, the memory allocation area may change from time to time or computer to computer.) |
