Crowds outside the Melbourne court cheered shortly after 9.30am when Justice Ferguson announced two of the court's three judges found it was not unreasonable for a Victorian jury in December to find Pell guilty of offences against two boys in 1996.

Justice Ferguson delivered the landmark decision via a livestream link to a world audience against a man who was once the third most senior member of the Catholic Church. Pell was returned to jail shortly before 10am after Justice Ferguson read a summary of the lengthy decision. Pell was sentenced to a maximum six years jail in March.

After reviewing the facts of the case presented to the jury, Justice Ferguson and Justice Christopher Maxwell found "We did not experience a doubt" that the offences had occurred.

The two judges found a former choirboy who was a key prosecution witness against Pell was a "compelling witness, was clearly not a liar and was a witness of truth".

"Throughout his evidence the complainant came across as a person telling the truth. Some things he could remember and many things he could not. His explanations had the ring of truth," Justice Ferguson said.

Justice Mark Weinberg dissented with the majority view and found the complainant's evidence of the second offence was not plausible and there was doubt about the jury decision.

All three judges refused two other appeal grounds by Pell, including that a judge erred in not allowing an animation developed by the Pell side, of St Patrick's Cathedral where the offences occurred, to be put to the jury.

All three judges found the animation presented a "distorted picture" of what occurred because it included the presence of other priests, despite "no evidence of any kind" during the trial to say there were others present apart from Pell and the choirboys.

"It was plainly intended to implant in the minds of the jury that the complainant's account could not have been possible because there were (other) priests present in the area," Justice Ferguson said.

The animation had the potential of misleading or at least confusing the jury and the presiding judge was correct in ruling it could not be shown, the appeal court found.

The three judges also rejected Pell's third appeal ground, that there was a fundamental irregularity in the trial process because he was arraigned - entered his not guilty plea - while the jury was not present in the courtroom.

The three judges refused the appeal because the jury viewed the arraignment from another courtroom via audio-visual link.

Pell was jailed for offences during his time as Archbishop of Melbourne.

He was convicted of orally raping a choirboy, 13, in the sacristy at St Patrick's Cathedral and grabbing a 13-year-old choirboy's genitals in a hallway at the same church two months later.

One of the former choirboys was a key prosecution witness. The other died of an overdose in 2014 without ever complaining that he had been abused.

Pell has always maintained his innocence.

His appeal relied on key arguments outlined during earlier hearings.

Pell's lawyers argued he had an alibi, the attacks could not have happened where and when they did and a priest who could have given contradictory evidence was not interviewed.

His strongest appeal leg was that the jury was unreasonable in reaching the convictions but Justices Ferguson and Maxwell rejected all 13 of the submissions made by Pell's lawyers at appeal, that it was impossible or improbable that he abused the boys inside the cathedral..

The appeal decision comes several weeks after a letter purporting to be from Pell was circulated on social media earlier this month, against Victorian corrective services guidelines.

The letter, dated August 1, was circulated by supporters and said: "My faith in our Lord, like yours, is a source of strength".

"The knowledge that my small suffering can be used for good purposes through being joined to Jesus' suffering gives me purpose and direction," the letter said.

During his sentencing before County Court Chief Justice Peter Kidd Pell was told he was not to be made a scapegoat for any failings or perceived failings of the Catholic Church.

"I am not sitting in judgment of the Catholic religion or the Catholic Church," Judge Kidd said.