The codec owns the erasure math for both ends: protect_video_frame and
protect_audio_block on the producer, recover_video_block and
recover_audio_block on the consumer. Each block is systematic Reed-Solomon
over GF(2^8) (reed-solomon-erasure 6, default features), named on every
parity record by the scheme id rs-gf256-v1. Any <= m erasures recover
exactly; more report BeyondRepair. Video frames split into ceil(n/16)
near-equal blocks with m = max(2, ceil(k/4)); audio is 4+2. A frame's
records come back in send order, rotating one record from each block so a
burst lands as one loss per block.
Deleted first: gamecult.media_video_parity_shard.v2 and its XOR-stripe
validator, and the reliable "audio" channel (profile entry, send-options
arm, constant, tests). Audio now rides "media" with parity.
Added: gamecult.media_video_parity_shard.v3 (block geometry, scheme id,
shard length), gamecult.media_audio_parity_shard.v1, the AudioParity wire
variant with validation, and the parity record key now names the block.
Every shard is bounded at MEDIA_FEC_MAX_SHARD_PAYLOAD_BYTES (720) so its
wrapped record fits MEDIA_FEC_MAX_WIRE_BYTES (1431), measured with
identifiers of up to 32 bytes.
Tests pin: exhaustive recovery for every shipped (k, m) and 4+2, m+1
refusal, known-answer parity bytes for both paths, the datagram bound on
every record kind, send order, deadline carriage and decoder validation.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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