How to render a specific audio unit in a AUGraph

I setup an AUGraph which contains several audio unit.

I know that when I call AUGraphStart() the graph starts the rendering of all the audio unit. But I would like to be able to start the rendering of one specific AUFilePlayer.

Is it possible?

UPDATE

I saw in comment that my question lacked of details. I have the current setup for my AUGraph:

AUFilePlayer -> AUMixer -> AUOutput

I setup the AUFilePlayer with a specific AudioFileID.

When I start the graph I would like just to "start" the graph without having any sound. And later I would like to do something like: AUFilePlayer.Play() to start making sounds.

I don't know if it's possible...

UPDATE: workaround found

I think I found a workaround for this. See my answer for my details.

Solution

I found the following workaround:

When I setup my AUFilePlayer I set the value mFramesToPlay of the ScheduledAudioFileRegion struct to:

ScheduledAudioFileRegion audio_file_region;
/*... init values...*/
audio_file_region_.mFramesToPlay = 0;

instead of

audio_file_region_.mFramesToPlay = number_of_frames_for_the_audio_file;

That way when I start the graph, the AUFilePlayer doesn't play any sound.

Then I have a methods Play() where I set the right frames to play for the mFramesToPlay field.

I don't know if it's a good way to do this but it does its job.