pjmedia mem player has too slow frame time

KM
Kenneth Mathis
Thu, Sep 3, 2020 7:44 PM

Hi all

I am trying to create a mem player and capture to handle some PCMA data.
Now I got the capture working completely fine but not the playback.
The reason appears to be that the frame time is different between the two
despite a similar setup.
I measured ~20ms for capture and ~40ms for playback. Shouldn't the playback
also be 20ms?
Audio characteristics are:
Clock Rate: 8kHz
Samples per frame: 160
Bits per sample: 16
Channels: Mono (1)
Frame Time: (Samples per frame / Clock Rate) * 1'000 = 20mS
Now halving the samples per frame on the playback also half the frame time
but only half of the time.
Thus one time it's 20ms the next it's 40ms and the next it's 20ms again and
so on.
Also I have a certain amount of samples I need to get rid of so lowering
the number of samples doesn't really work here without choppy audio.
The code I used to create the ports and determine the frame times:
https://pastebin.com/U1Ju9csB
Is this a known issue or am I missing something? I would appreciate any
help.

Thanks and best regards
Kenneth Mathis

Hi all I am trying to create a mem player and capture to handle some PCMA data. Now I got the capture working completely fine but not the playback. The reason appears to be that the frame time is different between the two despite a similar setup. I measured ~20ms for capture and ~40ms for playback. Shouldn't the playback also be 20ms? Audio characteristics are: Clock Rate: 8kHz Samples per frame: 160 Bits per sample: 16 Channels: Mono (1) Frame Time: (Samples per frame / Clock Rate) * 1'000 = 20mS Now halving the samples per frame on the playback also half the frame time but only half of the time. Thus one time it's 20ms the next it's 40ms and the next it's 20ms again and so on. Also I have a certain amount of samples I need to get rid of so lowering the number of samples doesn't really work here without choppy audio. The code I used to create the ports and determine the frame times: https://pastebin.com/U1Ju9csB Is this a known issue or am I missing something? I would appreciate any help. Thanks and best regards Kenneth Mathis