"People thought I was drunk, on drugs, losing it," Smith said on the video. "I'm not losing it, America. I'm fine, happy."
"When I go out on stage, I always work it. I work the crowds," she said.
Last week, prosecutors showed the jury footage from the telecast, in which Smith's slurred speech raised questions about possible drug use.
Birkhead previously testified about his concerns that Smith was taking too many prescription drugs on a regular basis. He says she suffered a seizure the night before the show and was almost too sick to go on, but that he didn't see her take any drugs that night.
Smith's attorney and boyfriend, Howard K. Stern, and doctors Sandeep Kapoor and Khristine Eroshevich have pleaded not guilty to conspiring to provide Smith with large doses of pain killers and other medications. They are not accused in her 2007 death from a drug overdose.
The Associated Press contributed to this report.
