Abstract: The invention uses digital signal processing (DSP) techniques to synchronize an audio encoding process with a video synchronization signal. Namely, the encoder parameters of a DSP microchip are preset according to characteristics of an audio frame. A buffer temporarily stores the audio frame prior to sending it to an encoder. The buffer then transfers the frame in response to receiving a video synchronization signal in conjunction with authorization from a microprocessor. As such, the encoding sequence of the audio frame coincides with the video synchronization signal. Since the corresponding video frame is already slaved to the video synchronization signal, the audio samples are effectively processed in sequence with the video data. Prior to outputting the encoded audio frame to a multiplexor, the encoder sends a value to the microprocessor representing the difference between the end of the encoded audio frame and a second video synchronization signal.

Abstract: A system and method for effectively implementing fixed masking thresholds in an audio encoder device comprises a filter bank for filtering source audio data to produce frequency sub-bands, a lookup table for storing masking threshold corresponding to the frequency sub-bands, and a bit allocator for using the masking thresholds to identify and discard masked audio data to thereby reduce the total amount of audio data that requires processing.

Abstract: A system and method for effectively implementing fixed masking thresholds in an audio encoder device comprises a filter bank for filtering source audio data to produce frequency sub-bands, a lookup table for storing masking threshold corresponding to the frequency sub-bands, and a bit allocator for using the masking thresholds to identify and discard masked audio data to thereby reduce the total amount of audio data that requires processing.

Abstract: A system and method for preventing artifacts in an audio data encoder device comprises a filter bank for filtering source audio data to produce frequency sub-bands, a psycho-acoustic modeler for calculating signal-to-masking ratios for the source audio data, and a bit allocator for using the signal-to-masking ratios to assign a finite number of allocation bits to represent the frequency sub-bands. In the absence of a defined significant event, the bit allocator performs a sub-band forcing strategy, including a prebit allocation procedure, to prevent artifacts or discontinuities in the encoded audio data.

Abstract: An encoder comprising predictive coding means for encoding electronic signals input thereto is disclosed. The predictive coding means is adapted to operate in a first high prediction order mode and in a second lower prediction order mode. The predictive coding means operates in the first and second modes in dependence on an input electronic signal comprising a transient signal. Preferably, the second mode comprises a transient recovery sequence of prediction orders. The transient signal detector determines predictive coding gain as well as a difference in predictive coding gain for a sequential input signal exceeding a threshold. The prediction orders are gradually increased for subsequent signals until the first mode (high) prediction order is attained. A transmission of electronics signals provides for an indication of initiation of a second mode for the predictive coding. Circuitry is included for reception of the second mode initiate signal.

Abstract: A method of coding an audio electrical signal using backward adaptive prediction. A first time frame of the audio electrical signal to be coded is received and transformed into the frequency domain using a modified discrete cosine transform (MDCT). The resulting frequency spectrum has 1024 spectral components. Subsequent time frames of the audio electrical signal are then received and the MDCT is applied to each in turn so as to generate a stream of spectral data values for each spectral component. For each stream, a set of prediction coefficients is calculated for each spectral value using a predetermined number of previously received consecutive spectral values of the stream. Using the set of linear prediction coefficients, a predicted spectral value is generated and the error between the predicted spectral value and the corresponding actual spectral value calculated. The calculated errors provide a coded representation of the spectral value stream.