The two environment variables:
WSJT_RX_AUDIO_BUFFER_FRAMES
WSJT_TX_AUDIO_BUFFER_FRAMES
each can be defined to an integer number which will be used as the
suggested audio buffer size for Rx and Tx respectively. Not setting
the variable or setting it to zero or less will cause the default
buffer size to be used, which should be a good choice for most, if not
all, systems.
WSJT_TX_AUDIO_BUFFER_FRAMES takes the following values:
-1 - use Qt/system default
0 - use 200 mS (WSJT-X default)
+ve integer - value is number of frames at 48 kHz
-1 is likely to be a good choice on Windows and may macOS. 0 has
proven to be good on Windows. On Linux 0 may be OK but we need to try
other values.
The value is only a hint, the actual value used along with the period
size (the size of each chunk of samples requested by the system) is
printed in an info level diagnostic message at the start of each
transmission.
where possible audio devices that disappear are not forgotten until
the user selects another device, this should allow temporarily missing
devices or forgetting to switch on devices before starting WSJT-X to
be handled more cleanly. If all else fails, visiting the Settings
dialog and clicking OK should get things going again. Note that we
still do not have a reliable way of detecting failed audio out
devices, in that case selecting another device and then returning to
the original should work.
Enumerating audio devices is expensive and on Linux may take many
seconds per device. To avoid lengthy blocking behaviour until it is
absolutely necessary, audio devices are not enumerated until one of
the "Settings->Audio" device drop-down lists is opened. Elsewhere when
devices must be discovered the enumeration stops as soon as the
configured device is discovered. A status bar message is posted when
audio devices are being enumerated as a reminder that the UI may block
while this is happening.
The message box warning about unaccounted-for input audio samples now
only triggers when >5 seconds of audio appears to be missing or over
provided. Hopefully this will make the warning less annoying for those
that are using audio sources with high and/or variable latencies. A
status bar message is still posted for any amount of audio input
samples unaccounted for >1/5 second, this message appearing a lot
should be considered as notification that there is a problem with the
audio sub-system, system load is too high, or time synchronization is
stepping the PC clock rather than adjusting the frequency to maintain
monotonic clock ticks.
Enumerating audio devices with QAudioDeviceInfo::availableDevices()
takes a long time on Linux with pulseaudio. This change only
enumerates up to the selected device when configuring and only
enumerates the whole list when the Settings->Audio tab is current.
This change also warns with a message box when Tx is started with no
audio output device configured.
Fixed buffer sizes are used. Rx use s 3456 x 1st downsample rate x 5
audio frames of buffer space. On Windows this means that each
chunk (periodSize()) delivered from the audio stream is our initial
DSP processing chunk size, thus matching audio buffer latency exactly
with WSJT-X's own front end latency. This should result in optimal
resilience to high system loads that might starve the soundcard ADC of
buffers to fill and case dropped audio frames.
For Tx a buffer sufficient for 1 s of audio is used at present, on
Windows the period size will be set to 1/40 of that which gives
reasonably low latency and plenty of resilience to high system loads
that might starve the soundcard DAC of audio frames to render. Note
that a 1 s buffer will make the "Pwr" slider slow to respond, we may
have to reduce the Tx audio buffer size if this is seen as a problem.
This enforces an audio input device in the settings dialog since we
can't do anything without an input device. A nil audio output device
is allowed with a warning.
Adjusting these may help with audio drop-outs, particularly on slower
CPU systems or heavily loaded systems. Smaller buffer sizes leave less
margin for process interruptions, larger sizes waste resources that
could impact other processes.
