Widescreen signaling
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In television technology, widescreen signaling (WSS) is a digital metadata 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 to switch to the correct display mode.
PAL and SECAM[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 | 0 | - | - | - |
| 0 | 0 | 0 | 1 | 4:3 | Full | 576 |
| 0 | 0 | 1 | 0 | 16:9 | Letterbox top | 432 |
| 0 | 0 | 1 | 1 | - | - | - |
| 0 | 1 | 0 | 0 | 14:9 | Letterbox top | 504 |
| 0 | 1 | 0 | 1 | - | - | - |
| 0 | 1 | 1 | 0 | - | - | - |
| 0 | 1 | 1 | 1 | 14:9 | Full-height 4:3, framed to be "14:9-safe" | 576 |
| 1 | 0 | 0 | 0 | 14:9 | Letterbox centre | 504 |
| 1 | 0 | 0 | 1 | - | - | - |
| 1 | 0 | 1 | 0 | - | - | - |
| 1 | 0 | 1 | 1 | >16:9 | Letterbox deeper than 16:9 | <432 |
| 1 | 1 | 0 | 0 | - | - | - |
| 1 | 1 | 0 | 1 | 16:9 | Letterbox centre | 432 |
| 1 | 1 | 1 | 0 | 16:9 | Full-height 16:9 (anamorphic) | 576 |
| 1 | 1 | 1 | 1 | - | - | - |
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[edit]
525 line systems made a provision using pulses for signaling widescreen and some other parameters in a similar manner to PAL and SECAM. Players output them and NTSC compatible TVs (including multiformat) recognize them.
See also[edit]
References[edit]
- ETSI EN 300 294 "Television Systems: 625-Line Television Wide Screen Signaling (WSS)"
External links[edit]
- Renesas AN9716, Widescreen Signaling (WSS) covering 625 lines and 525 lines standard.