I Tried "Mali GPU Texture Compression Tool" for converrting my images from jpeg to etc1.
I Use the Following Params to achieve Pefect results with Jpeg Texture
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_NEAREST);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_NEAREST);
I user Follwoing Params with Etc1
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S,GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T,GL_CLAMP_TO_EDGE);
If it looks ok in the tool then it must be the way you're specifying the data. What is the format, RGB565? How many bits per pixel? Are you specifying that the texture is ETC compressed or is it still expecting uncompressed data? For example you should switch to calling glCompressedTexImage2D, with the internal format of ETC1_RGB8_OES if it's RGB888 data.
Thanks,
Chris