Hello all,
I'm writing an application where I should play parts of audio files. Each audio file contains audio data for a separate track.
These parts are sections with a begin time and a end time, and I'm trying to play those parts in the order I choose.
So for example, imagine I have 4 sections :
A - B - C - D
and I activate B and D, I want to play, B, then D, then B again, then D, etc..
To make smooth 'jumps" in playback I think it's important to fade in/out start/end sections buffers.
So, I have a basic AVAudioEngine setup, with AVAudioPlayerNode, and a mixer.
For each audio section, I cache some information :
- a buffer for the first samples in the section (which I fade in manually)
- a tuple for the AVAudioFramePosition, and AVAudioFrameCount of a middle segment
- a buffer for the end samples in the audio section (which I fade out manually)
now, when I schedule a section for playing, I say the AVAudioPlayerNode :
- schedule the start buffer (scheduleBuffer(_:completionHandler:) no option)
- schedule the middle segment (scheduleSegment(_:startingFrame:frameCount:at:completionHandler:))
- finally schedule the end buffer (scheduleBuffer(_:completionHandler:) no option)
all at "time" nil.
The problem here is I can hear clic, and crappy sounds at audio sections boundaries and I can't see where I'm doing wrong.
My first idea was the fades I do manually (basically multiplying sample values by a volume factor), but same result without doing that.
I thought I didn't schedule in time, but scheduling sections in advance, A - B - C for example beforehand has the same result.
I then tried different frame position computations, with audio format settings, same result.
So I'm out of ideas here, and perhaps I didn't get the schedule mechanism right.
Can anyone confirm I can mix scheduling buffers and segments in AVAudioPlayerNode ? or should I schedule only buffers or segments ?
I can confirm that scheduling only segments works, playback is perfectly fine.