Morgan Tsvangirai, Mugabe's only opponent in the vote, had already withdrawn from the poll citing a campaign of violence and intimidation against workers of his Movement for Democratic Change (MDC) by activists of the ruling Zanu-PF.
The video, which Yuda shot for The Guardian newspaper, is thought to be the first concrete evidence of actual vote fraud.
The footage shot inside the jail showed Yuda and his co-workers filling out ballots in favour of Mugabe on the election day while Zanu-PF supporters watched.
He also filmed Tendai Biti, the deputy MDC leader, being kept in chains while being held on treason charges.
Yuda also filmed voters at a Zanu-PF rally being told they should pretend to be illiterate so that their ballots could be marked in favour of Mugabe.
Yuda fled Zimbabwe after filming the video and is now hiding in a secret location.
The video emerged a day after Mugabe ruled out the prospect of talks with the MDC unless they acknowledge his victory in the one-man run-off.
Mugabe said on Friday that Tsvangirai should not "delude" himself into thinking the result of the poll could be expunged from the record books.
|Mugabe told his supporters that he would maintain a grip on the presidency [AFP]
"I am the president of the Republic of Zimbabwe and that is the reality," he told about 4,000 supporters who had gathered at Harare airport to welcome him back from an African Union (AU) summit in Egypt.
"Everybody has to accept that if they want to dialogue. If they agree on that, and we are satisfied, then we shall go into dialogue and listen to them by way of ideas, but those votes can never be thrown away."
The MDC has rejected Mugabe's demands as "unrealistic preconditions".
The run-off vote has been dubbed a "sham" both by the opposition and much of the international community.
Mugabe escaped serious censure from his peers at this week's AU summit, which instead ended with calls for the formation of a national unity government.
But Botswana has urged its neighbours not to recognise Mugabe's re-election and reiterated calls for Zimbabwe to be suspended from SADC, a regional bloc of 14 southern Africa nations.