Context: In addition, recording and reproducing an HDTV signal was a significant technical challenge in the early years of HDTV (Sony HDVS). Japan remained the only country with successful public broadcasting of analog HDTV, with seven broadcasters sharing a single channel.

Question: How many broadcasters did Japan have sharing a single channel?
Answer: seven

Question: Which country had successful public analog HDTV broadcasting?
Answer: Japan

Question: What was particularly challenging in the early years of HDTV?
Answer: recording and reproducing an HDTV signal

Question: What accomplishment in early HDTV did Japan have?
Answer: the only country with successful public broadcasting of analog HDTV

Question:  How many broadcasters did Japan have sharing a multi channel?
Answer: Unanswerable

Question:  Which country had successful public analog SDTV broadcasting?
Answer: Unanswerable

Question:  What was particularly challenging in the early years of SDTV?
Answer: Unanswerable

Question: What accomplishment in early SDTV did Japan have?
Answer: Unanswerable