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Welcome to the bgbtech_misc wiki!

Mostly still familiarizing myself with all this.

BTIC1x Family Codecs:

• BTIC1G
  • Older/Simpler byte-oriented low-complexity incremental codec.
  • Main use case is streaming video from robots.
    • It is more intended for low complexity rather than bitrate or quality.
    • It is mostly intended for incremental video streaming from ARM-based robot controllers.
• BTIC1H
  • Intended as a reasonably low-complexity image/video codec for fast encode/decode.
  • It isn't intended for the best possible bitrate or image quality.
    • It was originally mostly intended as a replacement for BTIC1G in the same basic use-case.
    • However, the design seems to also work passably for screen-capture and other things.
• BTIC4B
  • Similar in premise to BTIC1H, but uses 8x8 blocks.
  • This reduces per-block overhead, allowing for higher speeds than BTIC1H.
    • May achieve speeds high enough for 4K decoding in a single CPU thread on a modern CPU.
    • In some cases may also achieve high enough throughput to encode 4K in faster than real time (multithread).
• BTIC5A
  • Experimental "extra lightweight" codec (byte-based).
  • Conceptually Similar in premise to MS-CRAM, but gets better compression.
  • Uses a dynamic index-color palette.
  • Optional LZ post-compressor stage (RP2).
• BTIC5B
  • Intended to improve quality over BTIC5A, while still being fairly lightweight.
    • Replaces the palette with differential encodings within the RGB555 space.
  • Still uses a byte-oriented design, but switches over to using a pattern table and differential endpoints.
  • Intent is to be usable for video playback on a 50MHz BJX2 core or similar.
    • This was a problem for 1H and 4B, which were a bit heavyweight for this.
    • Single-threaded decode speeds on my PC can reach into Gpx/s territory.
  • Optional LZ post-compressor stage (RP2 or ULZ).

BTAC Audio Codecs

• BTAC1C
  • Modified MS-IMA-ADPCM
  • Generally fairly effective.
  • Adds predictive filters to allow improved audio quality.
  • Adds a joint-stereo mode to allow stereo at lower bitrates than normal ADPCM.
• BTAC2B
  • Possible fancier design (update: never did anything with this).

Data Compression:

• BTLZA / BTLZH
  • An extended form of Deflate supporting larger windows and matches.
  • It is a backwards-compatible binary superset of Deflate.
  • It was intended as a compromise between Deflate and LZMA.
    • Speed closer to Deflate, but compression closer to LZMA.
    • Thus far mostly used in Huffman only mode (BTLZH).
    • Conceptually, which term is used depends on whether or not AC is used.
• FeLZ32
  • Speed oriented DWORD-based LZ77 format.
  • Can have a faster decode speed than LZ4 at the expense of worse compression.
  • The cost to compression depends a bit on payload, generally with binary formats faring better.
  • Intended mostly for use-cases where encode/decode needs to happen quickly.
• BtRP2
  • RP2 is a simple Byte-Oriented LZ77 format.
  • It is able to (typically) get slightly better compression at similar decode speeds if compared with LZ4.
• TKuLZ
  • Intended to be a relatively simple and fast Huffman coded LZ77 variant.
  • It aims to be simpler and faster to decode than Deflate based designs.
  • It limits symbols to 12 bits, which is good for speed at a slight cost to compression.