bluetooth: Amend writeout to send more initial frames

When bluetooth transport has both both sink and source, pulseaudio would
synchronize writing out frames with reading frames from peer to make fair
schedule of reads and writes. Pulseaudio allows two blocks of data to be sent to
peer before synchronizing writes with reads just in case that peer implements
similar write schedule.

It could happen that first blocks are still missed by peer, which would cause
pulseaudio writes to stall waiting for first frames from peer.

Fix this by allowing more data frames out until data from peer is actually
received.

Closes: https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/issues/1424
Part-of: <https://gitlab.freedesktop.org/pulseaudio/pulseaudio/-/merge_requests/777>

1 files changed, 8 insertions, 2 deletions

diff --git a/src/modules/bluetooth/module-bluez5-device.c b/src/modules/bluetooth/module-bluez5-device.c
index ab1bc098e..dc6809ce5 100644
--- a/src/modules/bluetooth/module-bluez5-device.c
+++ b/src/modules/bluetooth/module-bluez5-device.c
@@ -1549,8 +1549,8 @@ static void thread_func(void *userdata) {
                     writable = true;
 
                 /* If we have a source, we let the source determine the timing
-                 * for the sink */
-                if (have_source) {
+                 * for the sink unless peer has not sent any data yet */
+                if (have_source && u->read_index > 0) {
 
                     /* If the stream is writable, send some data if necessary */
                     if (writable) {
@@ -1663,6 +1663,12 @@ static void thread_func(void *userdata) {
                             goto fail;
 
                         if (result) {
+                            if (have_source && u->read_index <= 0) {
+                                /* We have a source but peer has not sent any data yet, log this */
+                                if (pa_log_ratelimit(PA_LOG_DEBUG))
+                                    pa_log_debug("Still no data received from source, sent one more block to sink");
+                            }
+
                             writable = false;
                             have_written = true;
                         }