Widescreen signaling


In television technology, widescreen signaling is a digital stream embedded in the analog TV signal describing qualities of the broadcast, in particular the intended aspect ratio of the image. This can be used by a widescreen TV or other device to switch to the correct display mode.

PAL and SECAM Systems

For 625 scan line systems, the signal is placed in line 23. It begins with a run-in code and start code followed by 14 bits of information.

Group 1 (Aspect Ratio)

Group 2 (Enhanced Services)

The above settings are related to PALplus.

Group 3 (Subtitles)

b09b10Mode
00No subtitles
10Subtitles inside active image
01Subtitles outside active image
11Reserved

Group 4 (Other)

b12Mode
0No copyright asserted or status unknown
1Copyright asserted

NTSC Systems

525 line systems made a provision using pulses for signalling wide screen and some other parameters in a similar manner to PAL and SECAM. However, no video player generates them and no NTSC compatible TV recognises them. Accordingly, unless the wide screen is signalled via an alternate means, the TV has to be manually switched between 4:3 and 16:9.