g the speech coding tools. Lower bitrates, such as an average of 1.2 Kbps, are possible through variable rate coding. Low delay is possible for communications applications. When using the HVXC tools, speed and pitch can be modified under user control during playback. If the CELP tools are used, a change of the playback speed can be achieved by using an additional tool for effects processing. Synthesized Speech: Scalable TTS coders bitrate range from 200 Bps to 1.2 Kbps that allows a text, or a text with prosodic parameters (e.g., pitch contour, phoneme duration,), as its inputs to generate intelligible synthetic speech. General audio signals: Support for coding general audio ranging from very low bitrates to high quality is provided by transform coding techniques. With this functionality, a wide range of bitrates and bandwidths is covered. It starts at a bitrate of 6 Kbps and a bandwidth below 4 kHz, but also includes mono or multichannel broadcast quality audio. Synthesized Audio: Synthetic Audio support is provided by a Structured Audio Decoder implementation that allows the application of score-based control information to musical instruments described in a special language. Bounded-complexity Synthetic Audio: This is provided by a Structured Audio Decoder implementation that allows processing of a standardized Wavetable format. Examples of additional functionality include speed control, or change of the time scale without altering the pitch while decoding, and pitch change, or change of the pitch without altering the time scale while encoding or decoding. Audio Effects provide the ability to process decoded audio signals with complete timing accuracy to enable such functions as mixing, reverberation, and spatialization. Visual The MPEG-4 Visual standard will allow the hybrid coding of natural (pixel based) images and video together with synthetic (computer generated) scenes. This will, for example, allow the virtual presence of video communication participants. To this end, the Visual standard will comprise t