VP8EncStartAlpha  516 3rdparty/libwebp/enc/vp8enci.h int VP8EncStartAlpha(VP8Encoder* const enc);    // start alpha coding process
VP8EncStartAlpha  389 3rdparty/libwebp/enc/webpenc.c     ok = ok && VP8EncStartAlpha(enc);   // possibly done in parallel