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If you know your platform doesn't support BC7 or it's not necessary, be sure to set BASISD_SUPPORT_BC7=0. The tables for the mode 6 transcoder are very large (they bloat the compiled WebAssembly transcoder by around 400-500k). We'll probably be removing the mode 6 transcoder in a future update.
+The ATC format (which achieves nearly the same quality as BC1/BC3) is for Adreno mobile devices only, and most of these devices probably support one of the newer texture formats. On many platforms/devices/API's you can disable it.
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### Quick Basis file details
Internally, Basis files are composed of a non-uniform texture array of one or more 2D ETC1S texture "slices". ETC1S is a simple subset of the ETC1 texture format popular on Android. ETC1S has no block flips, no 4x2 or 2x4 subblocks, and each block only uses 555 base colors. ETC1S is still 100% standard ETC1, so transcoding to ETC1 or the color block of ETC2 is a no-op. We chose ETC1S because it has the very valuable property that it can be quickly transcoded to almost any other GPU texture format at very high quality using only simple per-block operations with small 1D lookup tables. Transcoding ETC1S to BC1 usually only introduces around .3 dB Y PSNR quality loss, with less loss for ETC1S->BC7. Transcoding to PVRTC1 involves only simple block level operations to compute the endpoints, and simple per-pixel scalar operations to compute the modulation values.
