U.S. Philips Corporation

Rudolf Hofmann

Karl Hellwig

Peter Vary

Peter Meyer

Wolfgang Brox

Digital transmission system with improved decoder in the receiver

Adaptive prediction filter using block floating point format and minimal

Audio coder/decoder with recursive determination of prediction

A telephone switching system, or teleconferencing arrangement, in which each participant hears all the other speakers but does not hear his own voice. The speech intensity of each participant is measured and subtracted from a signal which is based on the sum of all the other participants then speaking. This difference signal is then compared with a threshold to determine if this participant is rated 'speaking' (signal to be added for others to hear) or 'listening'. The speech intensity signal is multiplied by a weighing factor based on this comparison, before adding to the other weighted signals to form the sum signal.

Switching system comprising a conference arrangement

Devices for the digital recording and reproduction of speech signals are used, for example in answering apparatus. In order to reduce the quantity of data to be stored without noticeably affecting the acoustic quality of the speech, it is proposed to encode speech signals by means of a residual signal speech encoder.

Device for the digital recording and reproduction of speech signals

During algebraic summing of code words from conference participants to form a partial sum-code word overflow of the values may occur. Such an overflow can be prevented when prior to the adding operations the numerical range is extended and an adjustment of weighting factors is effected in dependence on the measured speech intensity of the partial sum-code word. By multiplying by these (attenuation) factors the outgoing subscriber-code word is mapped again on the original numerical range in the attenuation circuit. To reduce a noise level originating, for example, from line interferences, quantization errors, etc. subscribers which are currently not speaking can be attenuated in a further attenuation control circuit of the conference arrangement.

Method of and circuit arrangement for establishing conference

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Forchheim, Germany

Rudolf Hofmann