POST-ENCODING BITRATE REDUCTION OF MULTIPLE OBJECT AUDIO

摘要

A post-encoding bitrate reduction system and method for generating one more scaled compressed bitstreams from a single encoded plenary file. The plenary file contains multiple audio object files that were encoded separately using a scalable encoding process having fine-grained scalability. Activity in the data frames of the encoded audio object files at a time period are compared with each other to obtain a data frame activity comparison. Bits from an available bitpool are assigned to all of the data frames based on the data frame activity comparison and corresponding hierarchical metadata. The plenary file is scaled down by truncating bits in the data frames to conform to the bit allocation. In some embodiments frame activity is compared to a silence threshold and the data frame contains silence if the frame activity is less than or equal to the threshold and minimal bits are used to represent the silent frame.

主权项

1. A method for obtaining multiple scaled compressed bitstreams from a single plenary file, comprising:
separately encoding a plurality of audio object files to obtain a plurality of encoded audio object files at a plenary bitrate using a scalable bitstream encoder having fine-grained scalability that ranks bits in each data frame of the encoded audio object files in an order of psychoacoustic importance to human hearing; generating the plenary file at the plenary bitrate by combining the plurality of independently encoded audio object files and corresponding hierarchical metadata; constructing a first scaled compressed bitstream at a first target bitrate from the plenary file; and constructing a second scaled compressed bitstream at a second target bitrate from the plenary file such that multiple scaled bitstreams at different target bitrates are obtained from the single plenary file without any re-encoding of the plurality of encoded audio object files; wherein the first target bitrate and the second target bitrate are different from each other and are both less than the plenary bitrate.