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fsphil / hacktv

Analogue TV transmitter for the HackRF
GNU General Public License v3.0
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WSS tag is erroneously overlayed over image scrambled with Videocrypt #45

Closed Zcooger closed 5 years ago

Zcooger commented 5 years ago

WSS tag is stationary. Additionaly it is placed on wrong line since single line buffer is applied and in result it should land higher. I bet aspect ratio switch is working until the video is scrambled. After decoding WSS tag may be displaced and messed by the decoder so I suggest to:

  1. Overlay WSS tag first.
  2. Scramble the image.

Command I used: hacktv -m pal -t uint8 -o ebu_vc.bin --videocrypt free --wss auto ebu75.avi

ebu_vc

fsphil commented 5 years ago

No, this is the correct behaviour. Videocrypt decoders do not modify line 23.

fsphil commented 5 years ago

Normally videocrypt encoders will place the scrambled version of line 24 on line 23. hacktv doesn't do this in order to preserve the WSS signal. The result of this is that the WSS will actually appear twice in the descrambled output, an untouched version on line 23 and a 'descrambled' version on line 24.

Zcooger commented 5 years ago

Ok, thanks for clarification.