sRAW and mRAW store subsampled YCbCr in a lossless-JPEG frame cut into slices of whole MCUs. Reuse the subsampled lossless decoder added for Sony M/S ARW with Canon's per-component sequential prediction, re-chop the stream into image planes, and convert to linear white-balanced RGB with chroma gains measured per file against the camera's own IFD2 RGB. Render cache version 17.