Music and speech packed tight (9901)

MP3 chipset from MICRONAS INTERMETALL "understands" speech, too

Hanover, March 18, 1999 - At CeBIT '99 MICRONAS INTERMETALL presents a new variant of their successful MP3 chipset, consisting of the signal processor MAS 3507D and the D-A converter IC DAC 3550A. This chipset, which forms the heart of the now familiar MP3 players, can now decode speech compression formats, too. Possible applications include special terminal devices for voice recording and playback as well as combination units for playing back compressed music and speech.

Multifunctional terminal devices

Like the MP3 players already launched on the market, these terminal devices will be lightweight and mobile. They contain a flash memory, i. e. a semiconductor memory which can be recorded on any number of times, for example via the Internet or a microphone. The recordings can then be decompressed and played back in real time wherever required. The possible forms which this new class of device could take include dictating machines, audio book playback stations, communication terminals and combined MP3 and speech applications.

Effective speech compression

Apart from MPEG/Audio Layer 3 (MP3 for short), which is currently establishing itself as the leading standard for the compression of music, speech applications often rely on other compression formats, some of which are more effective. While 1 MB is sufficient to store around one minute of MP3-compressed music of CD quality, these formats allow to accom-modate between 5 and 20 minutes of speech in the same storage space. A typical total storage capacity of 64 MB would therefore suffice for a whole day's listening to an electronic reader.

In terms of distribution, too, there is a parallel between the availability of MP3 music and speech tracks. On the Internet, for example, there are lots of opportunities for downloading so-called audio books and learning media, most of which are coded with proprietary compression standards.

Multilingual decoder

The audio signal processor MAS 3507D can decode both MP3 and proprietary compression formats in real time, provided that the IC is prepared for all data formats of the application concerned. This is done very simply by means of a software package which MICRONAS INTERMETALL makes available to the developers of the playback equipment. The software includes an authoring system with which the speech files are provided with additional information on the data format. The decoder uses this information to select the appropriate de-com-pression method during playback.

The DAC 3550A is a D-A converter for analog audio output which has been specially optimized for this application. Outputs for amplifier and headphones are integrated. The signal processing of the chipset is controlled via an I2C bus. Thanks to their low power consumption, the ICs are ideal for use in battery-operated equipment.

Standard delivery and available package types

The MAS 3507D and the DAC 3550A are available in the 44-pin QFP package.

To support system developers, MICRONAS INTERMETALL offer a functional and fully documented application board, comprising the decoder, D-A converter and controller as well as headphones output and amplifier. Furthermore, a software package is available for the development of speech applications, comprising Windows audio plug-ins and DSP download software.