Widescreen signaling

Widescreen signaling

In television technology, widescreen signaling (WSS) is a digital stream embedded in the 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.

Contents

  • PAL and SECAM Systems 1
    • Group 1 (Aspect Ratio) 1.1
    • Group 2 (Enhanced Services) 1.2
    • Group 3 (Subtitles) 1.3
    • Group 4 (Other) 1.4
  • NTSC Systems 2
    • Word 0 2.1
    • Word 1 2.2
    • Word 2 2.3
  • See also 3
  • References 4
  • External links 5

PAL and SECAM Systems

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)

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)

b04 Mode
0 Camera Mode
1 Movie Mode
b05 Mode
0 PAL Standard
1 Colour Plus
b06 Mode
0 No Vertical helper
1 Vertical helper present
b07 Ghost cancellation

Group 3 (Subtitles)

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)

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

525 scan line systems (PAL-M and NTSC) put the WSS data in lines 20 and 283. A start code consisting of the bits "10" is used, followed by 14 bits of information.

Word 0

b0 Aspect Ratio
0 4:3
1 16:9
b1 Mode
0 Normal
1 Letterbox

b2-b5 all have the value "0".

Word 1

b6-b9 are reserved and all have the value "0".

Word 2

b10-b13 are reserved and all have the value "0".

See also

References

  1. ^ http://www.divitec.ses/default/files/microvideo_wss-dec.pdf
  • ETSI EN 300 294 "Television Systems: 625-Line Television Wide Screen Signaling (WSS)"

External links

  • PDF of WSS standard
  • PDF of WSS in 625 lines and 525 lines standard