[vdr] Re: Slowmotion

[s.huelswitt@gmx.de (Stefan Huelswitt)]

On 03 Jun 2004 Klaus Schmidinger <Klaus.Schmidinger@cadsoft.de> wrote:
> Christian Gmeiner wrote:
>> > > i have here a question again :) If i press pause in replay mode and
>> press then forward or backward this function is called:
>> > >
>> > >   virtual void TrickSpeed(int Speed);
>> > >        ///< Sets the device into a mode where replay is done slower.
>> > >        ///< Every single frame shall then be displayed the given number
>> of
>> > >        ///< times.
>> > >
>> > > I am correct?
>> > >
>> > > Now i want to know what values Speed can have.
>> >
>> > int cDvbPlayer::Speeds[] = { 0, -2, -4, -8, 1, 2, 4, 12, 0 };
[...]
>> 
>> TrickSpeed is only called for slowmotion or is it also called for fast
>> forward. I think it is not only for
>> slowmotion, because of the high numbers in Speeds (-8, 12).
> 
> From the comment:
> 
>       ///< Sets the device into a mode where replay is done slower.
>       ///< Every single frame shall then be displayed the given number of
>       ///< times.
> 
> This means that it will only be called for slow motion ("Sets the device
> into a mode where replay is done _slower_") and that higher numbers mean
> slower replay (ok, maybe the name "Speed" is badly chosen...).

The argument of cDevice::TrickSpeed and cDvbPlayer::Speeds[] are not
directly related.

The argument for cDevice::TrickSpeed (which AFAIK can be 0-63) is
calculated inside cDvbPlayer::TrickSpeed. In the Speeds[] array
mit middle 1 is for normal replay, negatives for slowmotion and
positives for fast forward (as a real speed indicator).

For calculating the real calling argument for cDevice::TrickSpeed
you have to take into account that in fast forward, fast rewind
and rewind slow motion only I-frames are played. Assuming that
there is an I-frame every 12th frame, the calling argument is
-value*12 for negative values (slowmotion) and 12/value for
positive values (fast forward/rewind).

Regards.

-- 
Stefan Huelswitt
s.huelswitt@gmx.de  | http://www.muempf.de/