CD Format

• Red Book is the standard for audio CD's across the world. The standard, which has remained relatively unchanged since its inception in 1980, was created two years before the first CD players came out.
  
  

CD Specifications

• All audio CD's must have the same specifications to technically be called an audio CD. The most notable of these specifications is that they cannot be longer than 79 minutes, they cannot have more than 99 tracks and no track can be less than 4 seconds in length.
  
  

Technical Restrictions

• There are also several technical restrictions that all CD's must follow. All audio must be encoded as 2-channel 16-bit LPCM (linear pulse code modulation) with a sample rate of 44,100 hertz. The bit rate must also be consistent at 1,411.2 kilobytes per second. These audio standards are standard across all CDs, regardless of where they are made.
  
  

Burned Media Support

• While all car CD players support the basic audio CD format, some older players may not completely support burned CD media such as CD-R and CD-RW. The playback of a burned CD on older car CD players may skip frequently, or the player may reject the CD entirely.
  
  

MP3 Support

• Many newer car CD players support MP3 CD's in addition to traditional audio CD's. MP3 CD's are data discs that have MP3 files on them; an MP3 CD can contain hundreds of songs, although the audio may be below CD quality.