Lists

Open Menu Close Menu

Terms and Conditions
Lists hosted on this site
Email the Postmaster
Tips for posting to public mailing lists

Re: AVAudioPlayerNode - Mix between schedule buffers and segments

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: AVAudioPlayerNode - Mix between schedule buffers and segments

Subject: Re: AVAudioPlayerNode - Mix between schedule buffers and segments
From: Vincent CARLIER <email@hidden>
Date: Mon, 03 Apr 2017 14:44:35 +0200

More details on the way I compute positions in audio files :

First I get the file processing format. Next, for each start/end of audio sections in my file, I compute a frame position like so:

position = AVAudioFramePosition(time * format.sampleRate)

where time is a value in seconds.

Now I will break my audio sections in 3 parts :

[.buffer ] - [ segment ] - [ buffer ]

Start and end buffers are of length 1024, and I allocate them with that size.

Then I compute a frame start position for the segment : segmentStart = sectionStartPosition + 1024

I do the same for the end frame position of the segment : segmentEnd = sectionEndPosition - 1024

I deduce the length in frames of the segment being : AVAudioFrameCount(segmentEnd - segmentStart)

Is that right ?

2017-03-31 9:04 GMT+02:00 Vincent CARLIER <email@hidden>:

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.

 _______________________________________________
Do not post admin requests to the list. They will be ignored.
Coreaudio-api mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:

This email sent to email@hidden

Index(es):
- Date
- Thread