Per-frame entity and playerState blocks are compressed with LZ4
when svdemo_compress is set (default: 1). The block format writes
[original_size][compressed_size][data] — compressed_size=0 means
uncompressed. Playback auto-detects based on header flags.
Demo format bumped to version 2 with SVDEMO_FLAG_COMPRESSED flag.
Version 1 (uncompressed) demos are no longer compatible.
Uses the lz4.c/lz4.h library already in the server code directory.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>