It does not support the compression of images with Alpha components, although there are work-arounds for this.
[3] ETC1 takes 4x4 groups of pixel data and compresses each into a single 64-bit word.
[citation needed] Android version 2.2 (Froyo) includes support for ETC1.
The following four EAC codecs are included as mandatory in OpenGL ES 3.0 and OpenGL 4.3: The RGBA and RG11 formats are encoded in 128 bits per 4x4 block, while the rest are encoded in 64 bits per block.
A software utility called ETCPACK for compression and decompression of ETC1/ETC2 textures is available for free download in code form from Ericsson on GitHub.