Distribution links are those used to transport the video signal from the final production centres (end of the contribution chain) to the final head-ends that will carry out the Broadcasting through the different media to the final users.
It is therefore considered that the video signal will not undergo further encoding and, consequently, the encoding applied in this stretch is much more aggressive, with the purpose of achieving a significant reduction of the bandwidth required for its Broadcasting.
Although this encoding is not recommended for Multi-Generation processes (as described in the Contribution section), it maintains suitable quality levels for their viewing by the final user. Apart from the significant bit rate reduction, and taking advantage of the characteristics of the human visual perception system, which is less sensitive to colour than it is to luminance, the encoding profiles used are 4:2:0. These profiles reduce part of the colour information, allowing to reduce the bandwidth required for their encoding and broadcasting.
Another distinguishing point of the distribution link is that in this part of the chain it is necessary to insert additional service information to be broadcasted in the so-called digital multiplex, such as the DVB/ATSC/ISDB, teletext, AFD signalling, etc.
The table on the right shows the case of the broadcasting network for DTTV.
Sapec offers Encoding and Decoding devices with 4:2:0 profiles, both for MPEG-2 and H.264 encoding.