Avelune Audio Candidate 0.0
Historical Avelune audio codec experiments, retained for provenance and superseded by Draft Generation 1.
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Warning
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HISTORICAL / NON-NORMATIVE: superseded by the Draft Generation 1 |
Status: EXPERIMENTAL / NOT FROZEN
Intended architecture
The main research direction is a general-purpose lapped transform codec with explicit band energies and optional short-term/pitch whitening before the common transform path. It is not frozen.
Initial target configuration is 48 kHz mono/stereo with nominal 20 ms framing and shorter transform partitions for transients.
Experiment 0: lossless predictive PCM
The executable bring-up format deliberately starts with a simple custom codec rather than embedding an existing codec or treating PCM as the final design.
Input samples are signed 16-bit integers. For each channel independently:
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the first sample is predicted as zero;
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subsequent samples are predicted by the immediately previous reconstructed sample for the same channel;
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the signed residual is mapped by ZigZag coding;
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the unsigned value is encoded as bounded LEB128.
Predictor state MUST reset at every epoch boundary.
This experiment is useful for packetization, synchronization, truncation handling and exact round-trip tests. It is not the intended lossy audio architecture.