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+# Improved JPEG decoder implementation
+
+This subdirectory contains a JPEG decoder implementation that is API and ABI
+compatible with libjpeg62.
+
+*NOTE*: This is still a work in progress, currently only API functions called
+from libjxl's benchmark_xl tool are implemented.
+
+To decompress an ```input.jpg``` file with this new library:
+
+```
+(from the libjxl root directory)
+$ ./ci.sh opt
+$ LD_PRELOAD=./build/libjpeg.so.62 ./build/tools/benchmark_xl --input input.jpg --codec=jpeg --decode_only --save_decompressed --output_dir .
+```
+
+The decompressed file will be saved as ```input.jpg.jpeg.png```.
+
+To benchmark the jpeg encoding-decoding round-trip on an ```input.png``` with
+the new library, first build a statically linked ```cjpeg-static``` binary,
+which is found in ```$PATH```, and then run:
+
+```
+(from the libjxl root directory)
+$ ./ci.sh opt
+$ LD_PRELOAD=./build/libjpeg.so.62 ./build/tools/benchmark_xl --input input.png --codec=jpeg:cjpeg-static:q90
+```
+