E-MAC is 16:9 version of C-MAC

C-MAC

C-MAC is the variant approved by the European Broadcasting Union for satellite transmissions. The digital information is modulated using 2-4PSK , a variation of quadrature PSK where only two of the phaser angles are used....

. Originally E-MAC was designed for 15:9 pictures, it later adopted the 16:9 aspect ratio. The format is backwards compatible with C-MAC. It embeds additional information in field blanking and line blanking signals. E-MAC has a lower data capacity because of this methodology. The format includes a 'steering' signal to indicate to the 16:9 receiver the location of the 4:3 picture information. E-MAC receivers then stitch

Image stitching

Image stitching or photo stitching is the process of combining multiple photographic images with overlapping fields of view to produce a segmented panorama or high-resolution image. Commonly performed through the use of computer software, most approaches to image stitching require nearly exact...

 the 4:3 and "helper" widescreen

Widescreen

Widescreen images are a variety of aspect ratios used in film, television and computer screens. In film, a widescreen film is any film image with a width-to-height aspect ratio greater than the standard 1.37:1 Academy aspect ratio provided by 35mm film....

data into a seamless 16:9 picture.