MPEG-4 Book, The

10.3. MPEG-4 CELP Coding

Like the other coding tools in the MPEG-4 standard, MPEG-4 CELP is defined by a normative bitstream syntax and a corresponding decoding process, whereas an example encoder is described in an informative annex [MPEG4-3]. This approach leaves room for application-specific encoder optimizations even after the finalization of the standard. In contrast to this solution, other standard CELP speech codecs—for example, the ITU-T G.723 series [G723]—also specify a normative encoder. MPEG-4 CELP is specified in a modular way and therefore fits well with the MPEG-4 toolbox approach. One benefit of this approach is high flexibility with respect to the range of covered bit rates and sampling frequencies. Thus, it can operate in a ...