Hi Arkadiusz,
On Sat, Oct 26, 2024 at 3:15 PM Arkadiusz Bokowy
<arkadiusz.bokowy@xxxxxxxxx> wrote:
>
> In order to properly synchronize audio/video playback it is required to
> report audio delay to the A2DP source. This commit allows connected
> media application to update the Delay property of the A2DP transport
> which will inform remote source about the playback delay.
>
> The functionality was tested by streaming audio between two hosts
> running BlueZ Bluetooth stack.
> ---
> doc/org.bluez.MediaTransport.rst | 2 +-
> profiles/audio/transport.c | 87 +++++++++++++++++++++++++++++---
> 2 files changed, 82 insertions(+), 7 deletions(-)
>
> diff --git a/doc/org.bluez.MediaTransport.rst b/doc/org.bluez.MediaTransport.rst
> index 5da13b3b5..310a69c6f 100644
> --- a/doc/org.bluez.MediaTransport.rst
> +++ b/doc/org.bluez.MediaTransport.rst
> @@ -125,7 +125,7 @@ uint16 Delay [readwrite, optional]
>
> Transport delay in 1/10 of millisecond.
> This property is available only if the DelayReporting is true and is
> - writeable only when the transport was acquired by the sender.
> + writeable only when the transport corresponds to a sink endpoint.
I don't think we should allow changes to the Delay by any application
since this might introduce problems to the streaming, so Id say this
policy should stay, if you are trying to control this via bluetoothctl
then also acquire the stream via bluetoothctl.
> uint16 Volume [readwrite, optional]
> ```````````````````````````````````
> diff --git a/profiles/audio/transport.c b/profiles/audio/transport.c
> index dd6878427..be34cc899 100644
> --- a/profiles/audio/transport.c
> +++ b/profiles/audio/transport.c
> @@ -116,6 +116,7 @@ struct media_transport_ops {
> void *(*get_stream)(struct media_transport *transport);
> int8_t (*get_volume)(struct media_transport *transport);
> int (*set_volume)(struct media_transport *transport, int8_t level);
> + int (*set_delay)(struct media_transport *transport, uint16_t delay);
> void (*update_links)(const struct media_transport *transport);
> GDestroyNotify destroy;
> };
> @@ -551,6 +552,36 @@ static int transport_a2dp_snk_set_volume(struct media_transport *transport,
> return avrcp_set_volume(transport->device, level, notify);
> }
>
> +static int transport_a2dp_snk_set_delay(struct media_transport *transport,
> + uint16_t delay)
> +{
> + struct a2dp_transport *a2dp = transport->data;
> + struct avdtp_stream *stream;
> +
> + if (a2dp->delay == delay)
> + return 0;
> +
> + if (a2dp->session == NULL) {
> + a2dp->session = a2dp_avdtp_get(transport->device);
> + if (a2dp->session == NULL)
> + return -EIO;
> + }
> +
> + stream = media_transport_get_stream(transport);
> + if (stream == NULL)
> + return -EIO;
> +
> + if (a2dp->watch) {
> + a2dp->delay = delay;
> + g_dbus_emit_property_changed(btd_get_dbus_connection(),
> + transport->path,
> + MEDIA_TRANSPORT_INTERFACE,
> + "Delay");
> + }
> +
> + return avdtp_delay_report(a2dp->session, stream, delay);
> +}
> +
> static void media_owner_exit(DBusConnection *connection, void *user_data)
> {
> struct media_owner *owner = user_data;
> @@ -900,6 +931,47 @@ static gboolean get_delay_report(const GDBusPropertyTable *property,
> return TRUE;
> }
>
> +static int media_transport_set_delay(struct media_transport *transport,
> + uint16_t delay)
> +{
> + DBG("Transport %s delay %d", transport->path, delay);
> +
> + if (transport->ops && transport->ops->set_delay)
> + return transport->ops->set_delay(transport, delay);
> +
> + return 0;
> +}
> +
> +static void set_delay_report(const GDBusPropertyTable *property,
> + DBusMessageIter *iter, GDBusPendingPropertySet id,
> + void *data)
> +{
> + struct media_transport *transport = data;
> + uint16_t arg;
> + int err;
This really needs to check that sender is the owner of the transport.
> + if (dbus_message_iter_get_arg_type(iter) != DBUS_TYPE_UINT16) {
> + g_dbus_pending_property_error(id,
> + ERROR_INTERFACE ".InvalidArguments",
> + "Expected UINT16");
> + return;
> + }
> +
> + dbus_message_iter_get_basic(iter, &arg);
> +
> + err = media_transport_set_delay(transport, arg);
> + if (err) {
> + error("Unable to set delay: %s (%d)", strerror(-err), err);
> + g_dbus_pending_property_error(id,
> + ERROR_INTERFACE ".Failed",
> + "Internal error %s (%d)",
> + strerror(-err), err);
> + return;
> + }
> +
> + g_dbus_pending_property_success(id);
> +}
> +
> static gboolean volume_exists(const GDBusPropertyTable *property, void *data)
> {
> struct media_transport *transport = data;
> @@ -1036,7 +1108,7 @@ static const GDBusPropertyTable transport_a2dp_properties[] = {
> { "Configuration", "ay", get_configuration },
> { "State", "s", get_state },
> { "DelayReporting", "b", get_delay_reporting },
> - { "Delay", "q", get_delay_report, NULL, delay_reporting_exists },
> + { "Delay", "q", get_delay_report, set_delay_report, delay_reporting_exists },
> { "Volume", "q", get_volume, set_volume, volume_exists },
> { "Endpoint", "o", get_endpoint, NULL, endpoint_exists,
> G_DBUS_PROPERTY_FLAG_EXPERIMENTAL },
> @@ -2196,7 +2268,7 @@ static void *transport_asha_init(struct media_transport *transport, void *data)
>
> #define TRANSPORT_OPS(_uuid, _props, _set_owner, _remove_owner, _init, \
> _resume, _suspend, _cancel, _set_state, _get_stream, \
> - _get_volume, _set_volume, _update_links, _destroy) \
> + _get_volume, _set_volume, _set_delay, _update_links, _destroy) \
> { \
> .uuid = _uuid, \
> .properties = _props, \
> @@ -2210,16 +2282,17 @@ static void *transport_asha_init(struct media_transport *transport, void *data)
> .get_stream = _get_stream, \
> .get_volume = _get_volume, \
> .set_volume = _set_volume, \
> + .set_delay = _set_delay, \
> .update_links = _update_links, \
> .destroy = _destroy \
> }
>
> -#define A2DP_OPS(_uuid, _init, _set_volume, _destroy) \
> +#define A2DP_OPS(_uuid, _init, _set_volume, _set_delay, _destroy) \
> TRANSPORT_OPS(_uuid, transport_a2dp_properties, NULL, NULL, _init, \
> transport_a2dp_resume, transport_a2dp_suspend, \
> transport_a2dp_cancel, NULL, \
> transport_a2dp_get_stream, transport_a2dp_get_volume, \
> - _set_volume, NULL, _destroy)
> + _set_volume, _set_delay, NULL, _destroy)
>
> #define BAP_OPS(_uuid, _props, _set_owner, _remove_owner, _update_links, \
> _set_state) \
> @@ -2227,7 +2300,7 @@ static void *transport_asha_init(struct media_transport *transport, void *data)
> transport_bap_init, \
> transport_bap_resume, transport_bap_suspend, \
> transport_bap_cancel, _set_state, \
> - transport_bap_get_stream, NULL, NULL, _update_links, \
> + transport_bap_get_stream, NULL, NULL, NULL, _update_links, \
> transport_bap_destroy)
>
> #define BAP_UC_OPS(_uuid) \
> @@ -2245,14 +2318,16 @@ static void *transport_asha_init(struct media_transport *transport, void *data)
> transport_asha_resume, transport_asha_suspend, \
> transport_asha_cancel, NULL, NULL, \
> transport_asha_get_volume, transport_asha_set_volume, \
> - NULL, NULL)
> + NULL, NULL, NULL)
>
> static const struct media_transport_ops transport_ops[] = {
> A2DP_OPS(A2DP_SOURCE_UUID, transport_a2dp_src_init,
> transport_a2dp_src_set_volume,
> + NULL,
> transport_a2dp_src_destroy),
> A2DP_OPS(A2DP_SINK_UUID, transport_a2dp_snk_init,
> transport_a2dp_snk_set_volume,
> + transport_a2dp_snk_set_delay,
> transport_a2dp_snk_destroy),
> BAP_UC_OPS(PAC_SOURCE_UUID),
> BAP_UC_OPS(PAC_SINK_UUID),
> --
> 2.39.5
>
>
--
Luiz Augusto von Dentz
