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+# PSn00bSDK MDEC library
+
+This is a fully open source reimplementation of the official SDK's "data
+compression" library. This library is made up of two parts, the MDEC API and
+functions to decompress Huffman-encoded bitstreams (.BS files, or frames in
+.STR files) into data to be fed to the MDEC. FMV playback is not part of this
+library (nor the official one) per se, but can implemented by using these APIs
+alongside some code to stream data from the CD drive.
+
+**Currently only version 1 and 2 bitstreams are supported**.
+
+## MDEC API
+
+The MDEC data input/output API is almost identical to the official one, with
+only two minor differences:
+
+- `DecDCTPutEnv()` takes a second argument specifying whether the MDEC shall be
+  put into monochrome or color mode (the original API only supported color).
+- A `DecDCTinRaw()` function was added for easier feeding of headerless data
+  buffers to the MDEC. This function does not affect how `DecDCTin()` works.
+
+## Decompression API
+
+The following functions are currently provided:
+
+- `DecDCTvlcStart()`, `DecDCTvlcContinue()`: a decompressor implementation that
+  uses a small (<1 KB) lookup table and leverages the GTE, written in assembly.
+  `DecDCTvlcCopyTable()` can optionally be called to temporarily move the table
+  to the scratchpad region to improve decompression speed.
+- `DecDCTvlcStart2()`, `DecDCTvlcContinue2()`: a different implementation using
+  a large (34 KB) lookup table in main RAM, written in C. The table must be
+  decompressed ahead of time using `DecDCTvlcBuild()`, but can be deallocated
+  when no longer needed.
+- `DecDCTvlc()`, `DecDCTvlc2()`: wrappers around the functions listed above,
+  for compatibility with the Sony SDK. Using them is not recommended.
+
+## SPU ADPCM encoding API
+
+The Sony library has functions that can be used to convert raw 16-bit PCM audio
+data to SPU ADPCM. These are currently unimplemented due to their limited
+usefulness, but might be added at some point.