DVB: avoid unnecessary tuning when already tuned to the target transponder

[Pekka Jääskeläinen <pekka.jaaskelainen@…>]

The tuner logic could check if there's a tuner already tuned to a transponder in which the target channel's PID is and avoid unnecessary retuning this way.

This could be a good way to speedup the somewhat slow channel change. I suppose Changeset 6657 is aiming towards this, am I right? I could help implementing/testing it. If there's something I could do, please tell.

[John Pullan <john.pullan@…>]

I believe it already does this. (tested with dvb-t in UK)

[pekka.jaaskelainen@…]

Since when? It takes about 3-5 secs to change to a channel (even if it's on same transponder), and has taken as long since I started using MythTV. It shouldn't take that long AFAIK in case no tuning is necessary.

I'm using DVB-C in Finland.

[John Pullan <john.pullan@…>]

Well I put some debug in, and as far as I can tell the code just checks to make sure it doesn't have to change transponder and then backs out (dvbchannel.cpp, TuneTransport and TuneOFDM).

Of course there could be some issue with dvb-C.

(Not getting confused with the prebuffering delay ?)

[anonymous]

Of course it can be the prebuffering. Still it feels too long. How long it is taking for you?

I try checking the methods you pointed out.

[anonymous]

Initial tuning to BBC 1

2005-07-25 22:18:39.256 DVB#0 Status: LOCK. 2005-07-25 22:18:39.256 DVB#0 Multiplex Locked 2005-07-25 22:18:40.380 DVB#0 Successfully tuned to channel 1. 2005-07-25 22:18:41.381 DVB#0 WARNING - No data from card in 1 second. 2005-07-25 22:18:41.401 DVB#0 Data read from DMX - This is for debugging with transform.c

2.2 Seconds

Change to BBC 2 (same multiplex)

2005-07-25 22:19:04.017 DVB#0 Multiplex Locked 2005-07-25 22:19:05.601 DVB#0 Successfully tuned to channel 2. 2005-07-25 22:19:05.627 DVB#0 Data read from DMX - This is for debugging with transform.c

1.5 Seconds

Change to ITV 1, (different multiplex)

2005-07-25 22:19:34.237 DVB#0 DVB signal c8c8 | snr 2d2d | ber 1fffe | unc 0 2005-07-25 22:19:34.543 DVB#0 Status: LOCK. 2005-07-25 22:19:34.544 DVB#0 Multiplex Locked 2005-07-25 22:19:35.426 DVB#0 Successfully tuned to channel 3. 2005-07-25 22:19:36.428 DVB#0 WARNING - No data from card in 1 second. 2005-07-25 22:19:36.447 DVB#0 Data read from DMX - This is for debugging with transform.c

2.2 seconds

[pekka.jaaskelainen@…]

Thanks. Are those also "perceived times", that is, the time from channel change command to actually be able to watch the new channel? If yes, then it's much faster for you, it seems.

[Isaac Richards]

This should have been marked invalid once it was obvious that this already happened.