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low-latency pulseaudio pipeline using --input-buffer #4

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low-latency pulseaudio pipeline using --input-buffer #4

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29 changes: 28 additions & 1 deletion src/pulseaudio.c
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,10 @@

#include <pulse/simple.h>
#include <pulse/error.h>
#include <pulse/timeval.h>

#define pa_memzero(x,l) (memset((x), 0, (l)))
#define pa_zero(x) (pa_memzero(&(x), sizeof(x)))

typedef struct {
pa_simple *pasp;
Expand All @@ -20,6 +24,13 @@ static int setup(sox_format_t *ft, int is_input)
char *app_str;
char *dev;
pa_sample_spec spec;

/* Pulseaudio will introduce a 250ms buffer if no buffer_attr is set
(https://github.com/pulseaudio/pulseaudio/blob/master/src/pulse/stream.c#L1028)
unless PULSE_LATENCY_MSEC environment variable is set.
Here we override this based on --input-buffer / --buffer command-line arguments
*/
pa_buffer_attr buffer_attr;
int error;

/* TODO: If user specified device of type "server:dev" then
Expand Down Expand Up @@ -62,8 +73,24 @@ static int setup(sox_format_t *ft, int is_input)
spec.rate = ft->signal.rate;
spec.channels = ft->signal.channels;

pa_zero(buffer_attr);
buffer_attr.maxlength = (uint32_t) -1;
buffer_attr.prebuf = (uint32_t) -1;
if (is_input) {
/* If the tlength/fragsize is not set, pulseaudio src/pulse/stream.c will
attempt to use getenv("PULSE_LATENCY_MSEC") and fallback on 250ms what
is likely to happen for the default pulseaudio input (--input-buffer defaults to 0)
ToDo: Add a pacat/parec-like --latency-msec option?
*/
buffer_attr.fragsize = sox_globals.input_bufsiz ? sox_globals.input_bufsiz : -1;
lsx_debug("INPUT cmd buffer size=%zu, pulseaudio buffer size=%u", sox_globals.input_bufsiz, buffer_attr.fragsize);
} else {
buffer_attr.tlength = sox_globals.bufsiz ? sox_globals.bufsiz : -1;
lsx_debug("OUTPUT cmd buffer size=%zu, pulseaudio buffer size=%u", sox_globals.bufsiz, buffer_attr.tlength);
}

pa->pasp = pa_simple_new(server, "SoX", dir, dev, app_str, &spec,
NULL, NULL, &error);
NULL, &buffer_attr, &error);

if (pa->pasp == NULL)
{
Expand Down