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bluez5: sco-io: send keepalive TX data if sink is not feeding it

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When using LC3-24kHz, remote device drops connection after a few seconds
if there is no sink playback.  Avoid this by sending silence, one TX
packet for each RX packet, if sink hasn't been feeding data within a
timeout.
This commit is contained in:
Pauli Virtanen 2025-09-27 11:55:32 +03:00 • committed by Wim Taymans
parent 3f9ae1ee10
commit 2248807835
1 changed files with 85 additions and 2 deletions
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87
spa/plugins/bluez5/sco-io.c
View file

@ -15,6 +15,7 @@
#include <spa/utils/list.h>
#include <spa/utils/keys.h>
#include <spa/utils/names.h>
#include <spa/utils/cleanup.h>
#include <spa/monitor/device.h>
#include <spa/node/node.h>
@ -51,6 +52,8 @@ SPA_LOG_TOPIC_DEFINE_STATIC(log_topic, "spa.bluez5.sco-io");
*/
#define MAX_MTU 1024
#define KEEPALIVE_NSEC (500 * SPA_NSEC_PER_MSEC)
struct spa_bt_sco_io {
uint8_t read_buffer[MAX_MTU];
@ -72,8 +75,57 @@ struct spa_bt_sco_io {
int (*source_cb)(void *userdata, uint8_t *data, int size, uint64_t rx_time);
void *source_userdata;
const struct media_codec *codec;
void *codec_data;
uint64_t last_tx_time;
uint64_t last_rx_time;
uint16_t keepalive_seqnum;
bool keepalive;
};
static void keepalive_send(struct spa_bt_sco_io *io)
{
static const uint8_t zeros[2048];
uint8_t buf[MAX_MTU];
int res, need_flush = 0;
size_t size;
if (io->codec->id == SPA_BLUETOOTH_AUDIO_CODEC_CVSD) {
/* Doesn't have fixed block size; TX same amount as RX instead */
size = SPA_MIN(sizeof(buf), io->read_size);
memset(buf, 0, size);
goto send;
}
size = res = io->codec->start_encode(io->codec_data, buf, sizeof(buf), ++io->keepalive_seqnum,
io->last_rx_time / SPA_NSEC_PER_USEC);
if (res < 0)
return;
do {
size_t encoded;
res = io->codec->encode(io->codec_data, zeros, sizeof(zeros),
SPA_PTROFF(buf, size, void), sizeof(buf) - size,
&encoded, &need_flush);
if (res < 0)
return;
size += encoded;
if (size >= sizeof(buf))
return;
} while (!need_flush);
send:
if (!io->keepalive)
spa_bt_sco_io_write_start(io);
io->keepalive = false;
spa_bt_sco_io_write(io, buf, size);
io->keepalive = true;
}
static void sco_io_on_ready(struct spa_source *source)
{
@ -107,6 +159,9 @@ static void sco_io_on_ready(struct spa_source *source)
}
io->read_size = res;
io->last_rx_time = rx_time;
if (!io->last_tx_time)
io->last_tx_time = rx_time;
if (io->source_cb) {
int res;
@ -115,6 +170,13 @@ static void sco_io_on_ready(struct spa_source *source)
io->source_cb = NULL;
}
}
/* If sink has not supplied packets for some time, for each RX packet send
* same amount of silence to keep the connection alive. Some devices (with
* LC3-24kHZ) require this and it doesn't hurt for others.
*/
if (io->last_tx_time + KEEPALIVE_NSEC < io->last_rx_time || io->keepalive)
keepalive_send(io);
}
read_done:
@ -157,11 +219,19 @@ int spa_bt_sco_io_write(struct spa_bt_sco_io *io, const uint8_t *buf, size_t siz
size_t packet_size;
int res;
io->last_tx_time = io->last_rx_time;
if (io->read_size == 0) {
/* The proper write packet size is not known yet */
return 0;
}
if (io->keepalive) {
/* Transition from keepalive to sink-fed data */
io->write_size = 0;
io->keepalive = false;
}
packet_size = SPA_MIN(SPA_MIN(io->write_mtu, io->read_size), sizeof(io->write_buffer));
if (io->write_size >= packet_size) {
@ -213,7 +283,8 @@ void spa_bt_sco_io_write_start(struct spa_bt_sco_io *io)
struct spa_bt_sco_io *spa_bt_sco_io_create(struct spa_bt_transport *transport, struct spa_loop *data_loop,
struct spa_system *data_system, struct spa_log *log)
{
struct spa_bt_sco_io *io;
spa_autofree struct spa_bt_sco_io *io = NULL;
struct spa_audio_info format = { 0 };
spa_log_topic_init(log, &log_topic);
@ -245,6 +316,15 @@ struct spa_bt_sco_io *spa_bt_sco_io_create(struct spa_bt_transport *transport, s
}
}
io->codec = transport->media_codec;
if (io->codec->validate_config(io->codec, 0, NULL, 0, &format) < 0)
return NULL;
io->codec_data = io->codec->init(io->codec, 0, NULL, 0, &format, NULL, transport->write_mtu);
if (!io->codec_data)
return NULL;
spa_log_debug(io->log, "%p: initial packet size:%d", io, (int)io->read_size);
spa_bt_recvmsg_init(&io->recv, io->fd, io->data_system, io->log);
@ -257,7 +337,7 @@ struct spa_bt_sco_io *spa_bt_sco_io_create(struct spa_bt_transport *transport, s
io->source.rmask = 0;
spa_loop_add_source(io->data_loop, &io->source);
return io;
return spa_steal_ptr(io);
}
static int do_remove_source(struct spa_loop *loop,
@ -279,6 +359,7 @@ void spa_bt_sco_io_destroy(struct spa_bt_sco_io *io)
{
spa_log_debug(io->log, "%p: destroy", io);
spa_loop_locked(io->data_loop, do_remove_source, 0, NULL, 0, io);
io->codec->deinit(io->codec_data);
free(io);
}
@ -290,4 +371,6 @@ void spa_bt_sco_io_set_source_cb(struct spa_bt_sco_io *io, int (*source_cb)(void
{
io->source_cb = source_cb;
io->source_userdata = userdata;
io->last_rx_time = 0;
io->last_tx_time = 0;
}