Australian Communications and Media Authority chair Nerida O'Loughlin told a Senate estimates hearing the authority had discretion on whether or not to find broadcasters in breach.

"Overall, we felt they had behaved incredibly responsibly," Ms O'Loughlin said.

"I would just like to clarify that the fact that we didn't choose to make breaches does not mean we didn't take the footage incredibly seriously."

Australian Brenton Tarrant, 49, has pleaded not guilty to 51 counts of murder, 40 counts of attempted murder and one charge of terrorism in relation to the shootings in March, which the gunman streamed live on Facebook as he targeted mosques.

Broadcasters used excerpts of this footage, as well as footage of victims, in their news bulletins.

The authority's deputy chair Creina Chapman said no broadcaster ever showed someone being shot, with the ABC not using the shooter's footage at all.

Ms Chapman said she'd like broadcasters to review their policies in light of the 24 news cycle.

"I think it's safe to say there's always areas of grey ... and the conclusion at the end of the day was the broadcasters did not cross the line," Ms Chapman said.

Ms O'Loughlin said the authority reviewed more than 200 hours of broadcast footage from the day of the shooting on Friday, March 15 until the following Monday.

She said they instead decided to engage with broadcasters directly to review where internal codes of practice had stood up and where they could be improved.

Australian Associated Press