Analog TV Receiver

The analog TV receiver app currently supports wideband amplitude-modulated PAL only. This signal used to be widely adopted for television broadcasts. The picture is assumed to be 625-line x 768-width interlaced but app reduces the image size to 52-line x 128-width to reduce processing overhead and to fit on the PortaPack screen. The resulting 52x128 image is then stretched to 104-line x 128-width for improved proportions, and multiple frames are displayed on top of one another in lieu of de-interlacing (i.e. the first image may be just the odd lines, the second may be the even lines, and repeat).

The app does not yet support sync signals detection, so frames may be misaligned both horizontally and vertically and will tend to drift over time. The picture can temporarily be aligned left/right by moving focus down to the screen area and turning the encoder dial to adjust the offset.

The app only shows black and white images (color images are received but are displayed in black and white).

It is important to manually adjust the amplification settings for improved picture contrast, since this is an amplitude-modulated signal and an automatic gain control is not yet implemented in software.

This app does not yet support NTSC, or SSTV.

References:

https://www.youtube.com/watch?v=VxBReLPbfZc

https://blog.csdn.net/shukebeta008/article/details/104741355