On 10/17/23 13:10, Ethan White wrote:
Hi,
How do I inform Bluez of my a2dp transport delay? The media-api
document shows a Delay property for the MediaTransport1 interface but
attempts at writing this property yield the following error:
org.freedesktop.DBus.Error.PropertyReadOnly: Property 'Delay' is not
writable
Reviewing profiles/audio/transport.c a2dp_properties (Bluez 5.70) I find
that the delay property does not have a set function:
line 846: { "Delay", "q", get_delay_reporting, NULL,
delay_reporting_exists },
What am I missing here? How an I supposed to inform the a2dp source of
my playback delay? Thanks for any help.
Regards,
Ethan
I'm currently using org.bluez.Media1 RegisterEndpoint to expose my a2dp
sink to a2dp sources. I use org.bluez.MediaTransport1 Acquire to get
the transport. I can write the 'Volume' property of
org.bluez.MediaTransport1 to change the audio source volume. However,
writing to the 'Delay' property of the org.bluez.MediaTransport1
interface yields only errors as this property appears to be read-only
despite bluez/docs/media-api.rst showing this property to be read/write.
When using busctl from the host running my a2dp sink to inspect the
transport I get a dash '-' in place of a numerical value:
host:~$ busctl introspect org.bluez
/org/bluez/hci0/dev_xx_xx_xx_xx_xx_xx/fd0
NAME TYPE SIGNATURE RESULT/VALUE
FLAGS
org.bluez.MediaTransport1 interface - -
-
.Acquire method - hqq
-
.Release method - -
-
.TryAcquire method - hqq
-
.Codec property y 2
emits-change
.Configuration property ay 6 128 1 4 131
232 0 emits-change
.Delay property q -
emits-change
.Device property o
"/org/bluez/hci0/dev_E8_78_65_F2_14_24" emits-change
.State property s "active"
emits-change
.UUID property s
"0000110b-0000-1000-8000-00805f9b34fb" emits-change
.Volume property q 64
emits-change writable
org.freedesktop.DBus.Introspectable interface - -
-
.Introspect method - s
-
org.freedesktop.DBus.Properties interface - -
-
.Get method ss v
-
.GetAll method s a{sv}
-
.Set method ssv -
-
.PropertiesChanged signal sa{sv}as -
-
Does Bluez allow an a2dp sink to report its playback delay to the a2dp
source via the org.bluez.MediaTransport1 Delay property? Is there some
other way to communicate this delay back to the audio source for proper
lip-sync with video?
Regards,
Ethan
