[lgwebos] channel number not always updated in case you switch between sources

[lolodomo]

If you use only the tuner source of your LG TV, the channel channel is updated as expected when your TV channel is changed.
But after switiching between sources and then coming back to the TV tuner, it can happen that the channel channel is no more updated.
I am not yet sure whether the trigger of the problem is the TV source not being the TV tuner when the binding is started.

[lolodomo]

I finally found how to reproduce this bug. It happens if I switch to HDMI3 and then come back to TV tuner. Note that I have no device connected to HDMI3.
Here are the logs:

18:44:58.200 [INFO ] [smarthome.event.ItemStateChangedEvent] - TvApplication changed from com.webos.app.hdmi3 to com.webos.app.livetv
18:44:58.211 [DEBUG] [g.lgwebos.internal.BaseChannelHandler] - LauncherApplication received: org.openhab.binding.lgwebos.internal.handler.core.LaunchSession@cf4382.
18:44:58.267 [TRACE] [ebos.internal.handler.LGWebOSTVSocket] - Message [in]: {"type":"response","id":3,"payload":{"subscribed":true,"appId":"com.webos.app.livetv","returnValue":true,"windowId":"","processId":""}}
18:44:58.277 [DEBUG] [webos.internal.handler.LGWebOSHandler] - postUpdate channelId appLauncher state com.webos.app.livetv
18:44:58.301 [TRACE] [ebos.internal.handler.LGWebOSTVSocket] - Message [out]: {"type":"unsubscribe","id":11}
18:44:58.313 [DEBUG] [g.lgwebos.internal.BaseChannelHandler] - Unsubscribed org.openhab.binding.lgwebos.internal.TVControlChannel on Thing: lgwebos:WebOSTV:tv
18:44:58.323 [TRACE] [ebos.internal.handler.LGWebOSTVSocket] - Message [out]: {"type":"subscribe","id":16,"uri":"ssap://tv/getCurrentChannel"}
18:44:58.335 [DEBUG] [g.lgwebos.internal.BaseChannelHandler] - Subscribed org.openhab.binding.lgwebos.internal.TVControlChannel on Thing: lgwebos:WebOSTV:tv
18:44:58.425 [TRACE] [ebos.internal.handler.LGWebOSTVSocket] - Message [in]: {"type":"response","id":16,"payload":{"returnValue":true}}
18:44:58.433 [INFO ] [ing.lgwebos.internal.TVControlChannel] - retrieving channel: ChannelInfo [channelId=null, channelNumber=null, channelName=null, channelType=null].

As you can see, the subscribe message is leading to an answer that does not include the expected channel information (values are null) and without the field subscribed in the payload.
Then if I change the channel with my remote control, no message is received and so of course the channel is not updated.

Here are the logs when it works:

18:42:05.325 [TRACE] [ebos.internal.handler.LGWebOSTVSocket] - Message [out]: {"type":"subscribe","id":11,"uri":"ssap://tv/getCurrentChannel"}
18:42:05.336 [DEBUG] [g.lgwebos.internal.BaseChannelHandler] - Subscribed org.openhab.binding.lgwebos.internal.TVControlChannel on Thing: lgwebos:WebOSTV:tv
18:42:05.444 [TRACE] [ebos.internal.handler.LGWebOSTVSocket] - Message [in]: {"type":"response","id":11,"payload":{"subscribed":true,"channelId":"1_25_15_15_2_515_8442","physicalNumber":25,"isScrambled":false,"channelTypeName":"Terrestrial Digital TV","isLocked":false,"dualChannel":{"dualChannelId":null,"dualChannelTypeName":null,"dualChannelTypeId":null,"dualChannelNumber":null},"isChannelChanged":false,"channelModeName":"Terrestrial","channelNumber":"15","isFineTuned":false,"channelTypeId":1,"isDescrambled":false,"isReplaceChannel":false,"isSkipped":false,"isHEVCChannel":false,"hybridtvType":null,"isInvisible":false,"favoriteGroup":null,"channelName":"BFM TV","channelModeId":0,"signalChannelId":"2_515_8442"}}

It looks like we could check whether the field subscribed is present and equal to true in the response. If not, we could implement a retry mechanism ?

If I switch to HDMI4 which is connected to a device and then again to the TV tuner, the problem is solved (the subscription is working).

[lolodomo]

@sprehn : WDYT about a retry mechanism for the subscriptions ?

Do you think it could be due to the subscription being requested too early after switching to tuner ? We could wait a little before requesting it in this case ?

[sprehn]

we could try it with a delay, it seems like a bug in webos to me. I did not get this to work for my setup, even with the recent fix provide. It only works when I start the tv on the tuner, even without delay.

[lolodomo]

I just tried again and now it work well !
But I think we should at least check the content of the subscription command response.

[lolodomo]

There is apparently no response to the unsubscribe request.
One idea: the unsubscribe and the subscribe rerquests are sent in a short sequence (around 20 ms).
Maybe we should add a little sleep in removeAnySubscription after the call to unsubscribe ?