ISO/IEC 13818 was prepared by SC29/WG11, also known as MPEG (Moving Pictures Expert Group). MPEG
was formed in 1988 to establish a standard for the coded representation of moving pictures and associated audio
stored on digital storage media.
ISO/IEC 13818 is published in three parts. Part 1 - systems - specifies the system coding layer of the standard. It
defines a multiplexed structure for combining audio and video data and means of representing the timing
information needed to replay synchronised sequences in real-time. Part 2 - video - specifies the coded
representation of video data and the decoding process required to reconstruct pictures. Part 3 - audio - specifies
the coded representation of audio data and the decoding process required to decode audio signals.
The technical changes in this 2nd edition compared to the first publication of ISO/IEC 13818-3 (1995) are:
1. In the first publication, certain combinations of dynamic crosstalk and prediction were not prohibited but not
practically implementable. In this 2nd revision, these combinations are explicitly prohibited.
2. In the first publication, a low-pass filter was to be applied to the monophonic surround signal in matrix
mode 2 (analogue surround mode). This filter is omitted in this edition, greatly simplifying the decoder.
3. The description of the syntax of the LFE channel was ambiguous. This description has been clarified.
Next to these technical changes, many editorial changes have been made, improving readability and clarity.
0.1 Extension of ISO/IEC 11172-3 Audio Coding to Lower Sampling Frequencies
In order to achieve better audio quality at very low bit rates (<64 kbit/s per audio channel), in particular if
compared with ITU-T (formerly CCITT) Recommendation G.722 performance, three additional sampling
frequencies are provided for ISO/IEC 11172-3 layers I, II and III. The additional sampling frequencies (Fs) are
16 kHz, 22,05 kHz and 24 kHz. This allows corresponding audio bandwidths of approximately 7,5 kHz,
10,3 kHz and 11,25 kHz. The syntax, semantics, and coding techniques of ISO/IEC 11172-3 are maintained
except for a new definition of the sampling frequency field, the bitrate index field, and the bit allocation tables.
These new definitions are valid if the ID bit in the ISO/IEC 11172-3 header equals zero. To obtain the best audio
performance, the parameters of the psychoacoustic model used in the encoder have to be changed accordingly.