Constant MAX_CHUNK_SIZE 

pub const MAX_CHUNK_SIZE: u32 = _; // 16_777_216u32

Largest chunk size ChunkAssembler::set_chunk_size/ChunkWriter::set_chunk_size will adopt from a Set Chunk Size protocol control message (§5.4.1): 16 MiB. The wire field is a 31-bit value (up to ~2 GiB), but no real publisher/player needs a chunk size anywhere near that — a single chunk this large would already hold many seconds of encoded audio/video — so this is a defensive ceiling, not a spec limit: values above it are clamped down rather than rejected, matching the existing floor-of-1 behaviour for values below it.