公开(公告)号：DE69712230T2

公开(公告)日：2002-10-31

申请号：DE69712230

申请日：1997-05-08

Applicant: ST MICROELECTRONICS ASIA

Inventor： ALVAREZ-TINOCO MARIO ,  GEORGE SAPNA ,  YANG HAIYUN

IPC: H04S1/00

Abstract: An audio decoder solution is here provided where a reduction in computing power is required. The proposed method consists of forcing the multiple output channels to only one type of inverse transformation format. A format of long transform length is more suitable for input signals whose spectrum remains stationary or quasi-stationary. This provides a greater frequency resolution, improved coding performance and a reduction of computing power required. Another format of two or more short transform lengths, possessing greater time resolution, is more desirable for rapidly changing signals with time. The computer power required for two or more short transforms should be higher than for only one transformation. The time versus frequency resolution trade-off should be considered when selecting a transform block length. Advantage is taken of human hearing behaviour to reduce the computing power of a processing engine (e.g. DSP) when downmixing from an M-channel input to a P-channel output is required. The encoder provides spectral information concerning the transmitted audio signal frame. This information corresponds to signals which are stationary/quasi-stationary or changing rapidly with time. Some analysis is required to decide which input channels are forced to long or short block conversion prior to frequency-domain downmixing and transformation.

公开(公告)号：DE69712230D1

公开(公告)日：2002-05-29

申请号：DE69712230

申请日：1997-05-08

Applicant: ST MICROELECTRONICS ASIA

Inventor： ALVAREZ-TINOCO MARIO ,  GEORGE SAPNA ,  YANG HAIYUN

IPC: H04S1/00

Abstract: An audio decoder solution is here provided where a reduction in computing power is required. The proposed method consists of forcing the multiple output channels to only one type of inverse transformation format. A format of long transform length is more suitable for input signals whose spectrum remains stationary or quasi-stationary. This provides a greater frequency resolution, improved coding performance and a reduction of computing power required. Another format of two or more short transform lengths, possessing greater time resolution, is more desirable for rapidly changing signals with time. The computer power required for two or more short transforms should be higher than for only one transformation. The time versus frequency resolution trade-off should be considered when selecting a transform block length. Advantage is taken of human hearing behaviour to reduce the computing power of a processing engine (e.g. DSP) when downmixing from an M-channel input to a P-channel output is required. The encoder provides spectral information concerning the transmitted audio signal frame. This information corresponds to signals which are stationary/quasi-stationary or changing rapidly with time. Some analysis is required to decide which input channels are forced to long or short block conversion prior to frequency-domain downmixing and transformation.

公开(公告)号：DE69738204D1

公开(公告)日：2007-11-22

申请号：DE69738204

申请日：1997-08-29

Applicant: ST MICROELECTRONICS ASIA

Inventor： SAPNA GEORGE ,  YANG HAIYUN

IPC: G10L19/02 ,  H04H40/18

Abstract: In order to reproduce audio signals which have been compressed or encoded for storage or transmission using, for example, MPEG audio encoding, a synthesis sub-band filter is employed which performs an inverse modified discrete cosine transform. The computational cost of the IMDCT implementation is reduced by pre-calculating arrays of sum and difference data. The arrays of sum and difference data are then used in two separate transform calculations, the results of which can be used in the generation of pulse code modulation audio data.