nx_flac_frame.nx

nx_flac_frame.nx -- FLAC frame and subframe decoding. Completes the FLAC decode path. nx_flac.nx holds the maths (Rice, fixed and LPC predictors, stereo decorrelation, CRC-8, the header tables); this reads an actual frame off a bitstream and turns it into samples. THE HEADER LENGTH IS NOT FIXED. A frame header is 4 bytes of flags, then a UTF-8-style extended number of 1-7 bytes, then optionally an 8- or 16-bit block size, then optionally an 8- or 16-bit sample rate, then the CRC-8. The CRC covers exactly those bytes and no more, so the parser has to know where it stopped. Hard-coding a length is the classic FLAC bug: it works on every small file (frame number < 128, standard block size and rate) and fails the moment a stream runs past frame 127. THE PARTITION SPLIT IS UNEVEN. Residuals are Rice-coded in 2^order partitions, and the FIRST partition is short by the predictor order because those samples are warm-up, already carried literally. Every later partition is full width. Splitting evenly decodes without error and desyncs the bitstream by exactly `order` samples. genealogy_id: flac_format_spec_frame lineage_id: nx_flac_frame_v1 license_tier: ORIGINAL