26 Jul
2017
26 Jul
'17
2:35 a.m.
On 26.07.2017 08:58, Yuri wrote:
jack_set_buffer_size limits frame size to the powers
of 2.
The Opus codec (http://opus-codec.org/) doesn't like such frame sizes.
It defines frame sizes in milliseconds, and allows 5 ms, 10 ms, 20 ms,
25 ms, ... which in case of 48,000 sample rate are never a power of two.
It seems like Jack shouldn't be so strict in limiting frame rates to
the powers of 2.
How to solve this problem?
Hi.
Which exact version of jack are you using?
afaik this depends on the driver and soundcard used.
I just tried here with latest jack2 using alsa hdmi output, I can use
1024 buffer size as usual, but also a few non-power-of-2 values as well.
falktx@falkTX-PC:~$ jack_bufsize
buffer size = 1024 sample rate = 48000
falktx@falkTX-PC:~$ jack_bufsize 1000
jack_set_buffer_size(): Unknown error -1
falktx@falkTX-PC:~$ jack_bufsize 800
falktx@falkTX-PC:~$ jack_bufsize 802
jack_set_buffer_size(): Unknown error -1
falktx@falkTX-PC:~$ jack_bufsize 870
jack_set_buffer_size(): Unknown error -1
falktx@falkTX-PC:~$ jack_bufsize 880
So some of those buffer sizes work, some do not.
GUIs usually show only power of 2 values because they're safer to use (I
mean, more likely to actually work).
Also some jack applications sadly were made with the expectation that
power-of-2 buffer sizes will be used...
But for such cases the application can return an error on start and
during the jack-buffersize-callback, to force jack to be under
power-of-2 sizes.
Anyway, at least in latest jack2 this is not a problem.
Not sure about jack1, but I believe the same is true.