Switching to Part-Time TV Channel Causes Long Timeout (1 Viewer)

CyberSimian

Test Group
  • Team MediaPortal
  • June 10, 2013
    2,849
    1,771
    Southampton
    Home Country
    United Kingdom United Kingdom
    In the UK we have a number of DVB-T and DVB-T2 channels which are part time, that is, they broadcast for only part of each day. During the times when they are not broadcasting, their bandwidth in the MUX is used by another part-time channel. This morning I tried to start live TV on the part-time channel which I had been watching last night, but which was not broadcasting this morning (I did not realise this until afterwards). I then had a very long wait, during which it seemed that MP had got stuck, but it did eventually timeout.

    I compared MP with the behaviour of my Humax PVR:

    (1) On the Humax, tuning from one active DVB-T2 channel to another active DVB-T2 channel takes 4 seconds.

    Tuning from one active DVB-T2 channel to an inactive DVB-T2 channel takes 10 seconds. After this period, the Humax displays a panel indicating when that channel is on-air (so this must be obtained from the broadcast data stream in some way).

    (2) On my HTPC using MP with TBS 6284 tuner cards, tuning from one active DVB-T2 channel to another active DVB-T2 channel takes 4 to 5 seconds (so similar to the Humax).

    Tuning from one active DVB-T2 channel to an inactive DVB-T2 channel takes 140 seconds, after which the screen shows "Unable to start time shifting; no video detected". During this period MP is unresponsive, so it is not possible to tune to a different channel until the timeout expires.

    Is it not possible for MP to detect quickly that a channel is not currently broadcasting, even though the MUX containing that channel is being received with normal signal strength? Are there any TV Server settings that could reduce this timeout? Thanks.

    I am using MP 1.9.0 pre, with aMPed skin, on 32-bit Vista.

    -- from CyberSimian in the UK
     

    mm1352000

    Retired Team Member
  • Premium Supporter
  • September 1, 2008
    21,577
    8,224
    Home Country
    New Zealand New Zealand
    Hello

    Tuning from one active DVB-T2 channel to an inactive DVB-T2 channel takes 140 seconds, after which the screen shows "Unable to start time shifting; no video detected". During this period MP is unresponsive, so it is not possible to tune to a different channel until the timeout expires.
    Are there any TV Server settings that could reduce this timeout?

    The quoted timeout (140 seconds) is extreme. It is trivial to reduce this significantly by configuration.

    140 seconds = 10 second [PMT timeout] x 2 [retry with PAT lookup] x 7 [tuners]

    You can reduce all 3 of those factors.

    PMT timeout can usually be set to 3 or even 2 seconds quite safely. That alone takes you from 140 down to 42 or 28 seconds.
    http://wiki.team-mediaportal.com/1_...n/TV-Server_Configuration/06_General#Scan_Tab

    If you set the PMT PID on all your tuning details to 0 or enable the "always use PAT lookup" debug option then you get rid of the PAT lookup retry. You're now down to 21 or 14 seconds.

    Finally, you can also specify the number of tuners for TV Server to try before giving up ("maximum free cards to try"):
    http://wiki.team-mediaportal.com/1_...ation/TV-Server_Configuration/08_Timeshifting
    http://wiki.team-mediaportal.com/1_...V-Server_Configuration/07_Recording#Recording

    The ultimate timeout result depends on how many tuners you want TV Server to try. Obviously if you set the limit to 1 you go as low as 3 or 2 seconds.

    Is it not possible for MP to detect quickly that a channel is not currently broadcasting, even though the MUX containing that channel is being received with normal signal strength?
    Yes... and TVE 3.5 (MP2 native TV) already does that.

    Regards,
    mm
     

    CyberSimian

    Test Group
  • Team MediaPortal
  • June 10, 2013
    2,849
    1,771
    Southampton
    Home Country
    United Kingdom United Kingdom
    The quoted timeout (140 seconds) is extreme. It is trivial to reduce this significantly by configuration.
    140 seconds = 10 second [PMT timeout] x 2 [retry with PAT lookup] x 7 [tuners]
    You can reduce all 3 of those factors.
    Excellent! My HTPC is recording a programme at the moment, but I will try adjusting those settings as soon as it has finished. Thank you.

    -- from CyberSimian in the UK
     

    Users who are viewing this thread

    Top Bottom