The MPEG-4 Audio Licensing Committee (ALC) have selected Via Licensing as the licensing administrator for the MPEG-4 Audio patent pool. This is a good thing, I suppose, but it’s troubling that MPEG-4 technology and content developers will have at least two “one-stop shops” for MPEG-4 patent portfolio licensing — MPEG LA for video and Via Licensing for audio.

The M4IF (MPEG-4 Industry Forum) asked the ALC to develop licensing terms for three audio profiles: High Quality Audio Profile, Speech Audio Profile and Mobile Audio Internetworking (“MAUI”) Profile. Additionally, the ALC will be working with Via Licensing to develop terms for other audio technologies that fall outside the three standard profiles.

The Speech Audio Profile will cover CELP (“Code Excited Linear Prediction”, a speech codec), HVXC (“Harmonic Vector Excitation Coding”, a speech codec) and TTSI (“Text-to-Speech Interface”, a standard way to control text-to-speech functionality).

The High Quality Audio Profile will cover AAC LC, AAC LTP, AAC Scalable, CELP, ER AAC LC, ER AAC LTP, ER AAC Scalable, ER CELP. AAC is an audio codec that works great for music, and CELP is a speech codec. (To deciper the notation tacked on before and after the codec names, see the paragraph after next.)

The Mobile Audio Internetworking Profile will cover these technologies: ER AAC LC, ER AAC Scalable, ER TwinVQ, ER BSAC, ER AAC LD. AAC (Advanced Audio Coding), TwinVQ and BSAC (Bit Sliced Arithmetic Coding) are audio/music codecs. (To deciper the notation tacked on before and after the codec names, see the next paragraph.)

The notation tacked on before and after the codec names are “tools”, which is an MPEG-ism for “features”. The LC tool is “low complexity”, which significantly reduces decoding complexity (say, for low-power devices) at the cost of a small quality hit. The LTP tool is “long-term prediction”, which provides significant quality improvements at the cost of being somewhta more complex to decode. The ER tool is “error resiliant”, and allows you to stream over lossy transports (like RTSP). The LD tool is “low delay”, which is handy for live streaming and other less-latency-is-better applications. The Scalability tool effciently encodes multiple audio bitrates into a single audio bitstream.

The ALC plans to deliver the MPEG-4 Audio Profile license agreements in Q1’03. | Dolby press release