Function decode_and_recommit 

fn decode_and_recommit<T: NodeType>(
    view: ViewNumber,
    common: &AvidmGf2Common,
    shares: &[AvidmGf2Share],
    payload_commitment: &VidCommitment2,
    metadata: &<<T as NodeType>::BlockPayload as BlockPayload<T>>::Metadata,
) -> Option<Vec<u8>>

Decode shares and return the payload bytes only if they re-commit to payload_commitment. Recovery alone does not bind the decoded bytes to the commitment: a Byzantine disperser can commit to a non-codeword, and a bad share poisons the erasure decoding.