U.S. Philips Corporation

Robbert G Van Der Waal

Raymond N Veldhuis

Leon Maria Van De Kerkhof

Marcel Breeuwer

Arnoldus W Oomen

Marc E Groenewegen

Gerrit J Keesman

Nicoline J Kiwiet

A transmitter provided with a subband coder is disclosed. The transmitter receives a wideband digital information at an input 1 and provides an output signal for transmission at an output (30). The input signal may have a varying sampling frequency (f.sub.g). The bitrate of the output signal is substantially constant. In order to compensate for the varying sampling frequency of the input signal, the transmitter is provided with a buffer memory (8) and a detector (18) for determining the filling degree of the memory (8). The control signal so derived, which is representative of the filing degree, is supplied to the bitallocation information generation unit (10). The bitpool B is varied in response to the control signal so as to control the filling degree to a nominal value, such as half full (FIG. 1). Further a receiver is disclosed for receiving the transmitted wideband digital information signal.

Transmitter for and method of transmitting a wideband digital

A display apparatus includes the switching unit for switching between an operating mode and a standby mode. The apparatus generates a picture on a display screen in the standby mode. The apparatus includes, for example a microphone for measuring a sound volume in the vicinity of the apparatus. The microphone is coupled to the picture-generating unit in order to change the picture in the standby mode in response to a change of the measured sound volume.

Apparatus comprising a display screen which is active in the operating

For encoding sound received as a stream of multibit input sample, from a finite length sequence of input samples, an instantaneous audibility threshold characteristic is determined. Next, a shaped, dither determined, signal is subtracted from the input samples to produce processing samples. Subtracting a dither signal dynamically ignores processing sample bits below the threshold. Next, quantization by a variable number of bits below the threshold is performed, while retaining all sample bits above the threshold. The ignored bits are replaced by the dither signal as buried channel bits at an adjustable number of bits per sample. Therefore, upgraded samples have non-ignored bits and buried channel bits are obtained and outputted. The noise is shaped through shape-filtering a difference between the upgraded samples and the processing samples, which shape-filtering may amend a received white-noise-like signal towards an actual threshold-versus-frequency characteristic.

Method and apparatus for coding digital sound by subtracting adaptive

Subband coding a digital signal having a first and a second signal component in a stereo intensity mode. The digital signal is subband coded to produce a first subband signal having a first q-sample signal block in response to the first signal component, and a second subband signal having a second q-sample signal block in response to the second signal component, the first and the second subband signals being in the same subband, and the first and second signal blocks being time-equivalent. The first and second signal blocks are processed to obtain a minimum distance value representative of a distance between a line and a plurality of points if (a) the points correspond to the respective pairs of time-equivalent samples in the first and second signal blocks, and are plotted in a coordinate system, and (b) the line is plotted such that it traverses the origin and the points at a minimum distance from the points in the coordinate system. When the minimum distance value is less than or equal to a threshold distance value, a composite signal block composed of q samples obtained by adding the respective pairs of time-equivalent samples in the first and second signal blocks together after multiplying each of the samples of the first signal block by cos(.alpha.) and each of the samples of the second signal block by -sin(.alpha.), where .alpha. is related to the angle formed between the line and a first axis of the coordinate system, are quantized.

Subband coding of a digital signal in a stereo intensity mode

For subband coding of a signal such as a digital stereo signal, the digital signal is split into subbands each comprising at least first and second subband signal components. The subband signal components in a subband m are constituted by blocks of q samples each, represented by a certain number of bits (n.sub.mr, n.sub.m1). The number of bits is the result of allocation based on a determination of bit needs for blocks in each subband. A determination is made whether or not initially bits are to be allocated to a signal block of one component in a subband prior to the bit allocation, and irrespective of the bit need for that signal block. If it is determined that an initial bit allocation is required for a particular signal block in a subband, an initial bit allocation is also applied to at least a second corresponding signal block in that subband.

Encoding system comprising a subband coder for subband coding of a

Transmitter, encoding system and method for subband coding a digital signal. The encoding system includes a splitter for dividing the digital signal into subband signals SB.sub.1, . . . , SB.sub.M ; a quantizer unit for quantizing time-equivalent q sample signal blocks of the subband signals; a bit need determiner and a bit allocator. The bit need determiner determines a bit need b.sub.m which corresponds to the number of bits by which the q samples in a time-equivalent signal block in a subband signal SB.sub.m should be represented, where 1.ltoreq.m.ltoreq.M. The bit allocator allocates n.sub.m bits to each of the q samples of the time-equivalent signal block of subband signal SB.sub.m on the basis of the bit need b.sub.m and an available bit quantity B, n.sub.m being the number of bits by which the q samples in the time-equivalent signal block of subband signal SB.sub.m will actually be represented, where 1.ltoreq.m.ltoreq.M.

Transmitter, encoding system and method employing use of a bit need

A system for subband coding of a digital audio signal x(k) includes in the coder (1) a filter bank (3) for splitting the audio signal band, with sampling rate reduction, into subbands (p=1, . . . P) of approximately critical bandwidth and in the decoder (2) a filter bank (5) for merging these subbands, with sampling rate increase. For each subband (p) the coder (1) comprises a detector (7(p)) for determining a parameter G(p;m) representative of the signal level in a block (p;m) of M samples of the subband signal x.sub.p (k) as well as a quantizer (8(p)) for adaptively block quantizing this subband signal in response to parameter G(p;m), and the decoder (2) comprises a dequantizer (9(p)) for adaptively block dequantizing the quantized subband signal s.sub.p (k) in response to parameter G(p;m). The quantizing characteristics are related to the noise-masking curve of the human auditory system, owing to which a high-quality of the replica x(k) of audio signal x(k) is attained with an average number of approximately 2.5 bits per sample for representing the output signals of the coder (1). The occasional audibility of quantizing noise in this replica x(k) is reduced effectively in that the coder (1) and decoder (2) contain identical bit allocation means (23, 24) responsive to a set of parameters G(p;m) for the higher group of subbands (p.sub.im .ltoreq.p.ltoreq.P) within an allocation window (FIG. 5) for allocating a number of B(p;m) bits per sample from a fixed predetermined number of B bits for this allocation window to the quantizer (8(p)) and the dequantizer (9(p)) for the block (p;m) of subband signal x.sub.p (k) and s.sub.p (k), respectively.

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Eindhoven, Netherlands

Robbert G Van Der Waal