Abstract
Several audio mixes are time-multiplexed, group by group, into fixed short blocks on one shared carrier. Bodypack receivers all receive the same carrier and each decodes only its own mix. Every mix is coded by a frameless constant-bit-rate codec, so each mix’s bits sit at fixed offsets and no stage waits for a codec frame. In the embodiment described, one transmitter drives one carrier in 4-level Gaussian frequency-shift keying (4-GFSK) at about 498 ksym/s (about 996 kb/s), in the transceiver’s synchronous direct mode, so the host streams bits continuously on the transceiver’s data clock and no packet handler is in the path. Time on the carrier is cut into fixed blocks of 333.3 µs, 3000 per second. Each block carries four groups of four audio samples per channel (83.3 µs at 48 kHz) for every mix on the carrier. Every mix’s codec is frameless: it emits a constant number of bits for every group and needs no lookahead. Within a block the mixes are interleaved group-major: a block descriptor, then every mix’s bits for group 0, then every mix’s bits for group 1, and so on, then per-mix resync fields, per-mix parity and a keyed tag. Because a group’s bits for every mix land together and each group has a fixed size, a receiver knows the bit offset of its own mix’s group before the block arrives and can decode it as soon as those bits are in.
Creative Commons License
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Recommended Citation
Anonymous, "Multiple audio mixes time-multiplexed group by group on one shared carrier: fixed short blocks, a frameless constant-bit-rate codec, per-receiver decoding of one mix, and a multichannel-per-MHz mode", Technical Disclosure Commons, ()
https://www.tdcommons.org/dpubs_series/12161