[vdr] channel-change-prediction, doable? stupid idea?

Udo Richter udo_richter at gmx.de
Fri Jan 23 14:55:03 CET 2009


On 21.01.2009 19:33, Gerald Dachs wrote:
> Assumed I have 2 free Tuners and I zapp through the channels of one
> tuner. Would it be possible to tune the 2. tuner to the same time to
> the after next channel in change direction, so that for the next
> channel change in the same direction it would be possible to
> channge to the 2. tuner instead of changing the channels of
> the 1. tuner

Channel switching delay is caused by two delays: First, the time to tune 
and lock the new transponder, second, the time till the next compressed 
stream starting point (I-Frame or audio syncword) is reached. This 
second time can be up to a second by its own.

To get instant switching, you would have to also decode the second 
stream in the background, so that the current frame is available the 
moment it is needed. Or you can buffer the last GOP of the stream and go 
back to that point on channel switch. You would have to ring-buffer up 
to one complete GOP permanently in memory to keep the delay from there on.

Both things are tricky to implement, require work on the output devices, 
and are probably not worth the effort.


Cheers,

Udo



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