| 摘要 |
Disclosed is a method for decoding a frame of an encoded digital audio signal. The frame comprises frame metadata, a first audio block (AB0) and one or more subsequent audio blocks (AB1-ABn) and each of the first and subsequent audio blocks (AB0-ABn) includes block metadata and encoded audio data for two or more audio channels (CH0-CH2). The encoded audio data comprises scale factors and scaled values representing spectral content of the two or more audio channels (CH0-CH2), each scaled value being associated with a respective scale factor. The block metadata includes control information describing coding tools used by an encoding process that produced the encoded audio data, the coding tools including adaptive hybrid transform processing. The adaptive hybrid transform processing includes applying an analysis filter bank implemented by a primary transform to the two or more audio channels (CH0-CH02) to generate primary transform coefficients, and applying a secondary transform to the primary transform coefficients for at least some of the two or more audio channels (CH0-CH02) to generate hybrid transform coefficients. The method includes receiving the frame of the encoded digital audio signal and examining the encoded digital audio signal of the frame in a single pass to decode the encoded audio data for each audio block (AB1-ABn) in order by block. The decoding of each respective audio block (AB1-ABn) includes determining for each respective channel of the two or more channels (CH0-CH02) whether the encoding process used adaptive hybrid transform processing to encode any of the encoded audio data. If the encoding process used adaptive hybrid transform processing for the respective channel (CH0-CH02) and if the respective audio block (AB0-ABn) is the first audio block (AB0) in the frame ration then all hybrid transform coefficients of the respective channel (CH0-CH02) for the frame from the encoded audio data in the first audio block (AB0) are obtained. An inverse secondary transform is applied to the hybrid transform coefficients to obtain inverse secondary transform coefficients and primary transform coefficients are obtained from the inverse secondary transform coefficients for the respective channel (CH0-CH02) in the respective audio block (AB0-ABn). If the encoding process did not use adaptive hybrid transform processing for the respective channel (CH0-CH02), primary transform coefficients for the respective channel (CH0-CH02) are obtained by decoding the encoded data in the respective audio block (AB0-ABn) and an inverse primary transform is applied to the primary transform coefficients to generate an output signal representing the respective channel (CH0-CH02) in the respective audio block (AB0-ABn). |
