“Fish” is a film by Iranian artist Abouzar Soltani, and it’s just premiered at a human rights festival in Eastern Europe. What’s unusual about “Fish” is that it was recorded in detention on the Hungarian-Serbian border, where Soltani and his 10-year-old son Armin have been stuck for almost a year. Soltani made “Fish” inside the detention center as a way to cheer up his son. The BBC’S Nick Thorpe reports.