Ayden Devereux, 26, operated the camera and could be heard encouraging the other offenders during a 17-minute recording of the incident at St Clair.
“More, next, next, next, next,” he said at one point.
The sentencing judge, Chris Hoy, described the offending as vile and revolting and said Devereux showed “no regard whatsoever” for the victim.
“It was gravely humiliating conduct,” he said.
The footage was uncovered when officers were investigating completely unrelated acts of graffiti two days later.
“These revolting acts may never have seen the light of day,” Judge Hoy said during sentencing.
‘She’ll do us one by one’
The court heard although Devereux did not touch the victim, his commentary suggested he was increasingly enthusiastic about what was happening.
“She’ll do us one by one,” Devereux said during the recording.
“The victim is motionless,” Judge Hoy said.
Two years after the gang rape and after seeing the video, apparently for the first time, Devereux decided to plead guilty.
He told a psychologist: “It’s shit. Wish I’d done something to stop it.”
The judge accepted there was no evidence Devereux knew of the victim’s intellectual impairment.
Devereux pleaded guilty to two counts of sexual intercourse without consent in company — an offence which carries a maximum term of 20 years.
He will spend at least five years in jail.
A juvenile was previously sentenced to at least three years in jail for his part in the gang rape, after himself pleading guilty.