Widescreen signaling

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

In television technology, widescreen signaling (WSS) 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[edit]

For 625 scan line systems (PAL and SECAM), the signal is placed in line 23. It begins with a run-in code and start code followed by 14 bits of information.[1]

Group 1 (Aspect Ratio)[edit]

b00 b01 b02 b03 Aspect ratio Picture placement Active lines
0 0 0 1 4:3 Full 576
1 0 0 0 14:9 Letterbox centre 504
0 1 0 0 14:9 Letterbox top 504
1 1 0 1 16:9 Letterbox centre 432
0 0 1 0 16:9 Letterbox top 432
1 0 1 1 >16:9 Letterbox deeper than 16:9 <432
0 1 1 1 14:9 Full-height 4:3, framed to be "14:9-safe" 576
1 1 1 0 16:9 Full-height 16:9 (anamorphic) 576

Group 2 (Enhanced Services)[edit]

b04 Mode
0 Camera Mode (interlaced)
1 Movie Mode (progressive scan)
b05 Mode
0 PAL Standard
1 Colour Plus
b06 Mode
0 No Vertical helper
1 Vertical helper present

The above settings are related to PALplus.


b07 Ghost cancellation

Group 3 (Subtitles)[edit]

b08 Mode
0 no subtitles
1 Teletext subtitles
b09 b10 Mode
0 0 No subtitles
1 0 Subtitles inside active image
0 1 Subtitles outside active image
1 1 Reserved

Group 4 (Other)[edit]

b11 Mode
0 No surround sound information
1 Surround sound mode
b12 Mode
0 No copyright asserted or status unknown
1 Copyright asserted
b13 Mode
0 Copying not restricted
1 Copying restricted

NTSC Systems[edit]

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 (including multiformat) recognises them. Accordingly, unless the wide screen is signalled via an alternate means (such as the wide screen discrete signal on SCART connection), the TV has to be manually switched between 4:3 and 16:9.

See also[edit]

References[edit]

  • ETSI EN 300 294 "Television Systems: 625-Line Television Wide Screen Signaling (WSS)"

External links[edit]