Reconstructing an image is usually based on a repetition of a key indicator, such as the beginning of the brightness of the sky. It then proceeds to lining up these indicators and all that follows until the indicator repeats.
Television being such a basic concept, presumably familiar to all developing species, a computer algorithm should be available on all space traveling vessels to enable a quick reconstruction ability to any discovery of a “video signal”, indicated by the structure of the signal, (Sky-Earth/Sky-Earth/Sky-Earth/ ...)
I always wondered about that on Star Trek. “Captain, I’ve got a visual ...”
Establishing a scale, in other words. "Sky" is a poor reference -- especially at night but consider dusk or dawn where it's in the middle of range of light-to-dark.
My experience of digital camera photos (esp. "RAW" photos, similar to film negatives) often starts with the range the camera acquired. THEN you process to full bright, full black, and the treatment of the range between. (I'm not going into HDR here...)
And yes, "I have a visual" indicates a preference for a traditional pixel-by-pixel (or equivalent analog) signal wth scan-line and frame delimiters. Not sure how that works under compression schemes...