[linux-dvb] Re: replay control in general

[Matthias Weingart <matthias@pentax.boerde.de>]

On Fri, Jul 27, 2001 at 09:44:27AM +0200, Klaus Schmidinger wrote:
> Stefan Huelswitt wrote:
> > 
> > On 26 Jul 2001 Matthias Weingart <matthias@pentax.boerde.de> wrote:
> > 
> > > A nice feature - 2x,3x times slower replay - if we make it
> > > slower, we also should think to make it faster too (skip some I-frames).
> > 
> > >> What if vdr would display every I-frame 4 times -> would give 3x speed;
> > >> 2 times -> 6 speed.
> > >
> > > This is another question: Does vdr play that I frames
> > > (1) with a certain (say 25fps) speed or
> > > (2) only as fast as it can?
> > 
> > As I see from the source, vdr is delivering the
> > i-frames as fast as possible, but I don't at which speed the
> > driver display them.
> 
> Yes, VDR delivers the I-frames to the driver at full speed.

And with this you have maybe different replay speeds at different fast
computers? Or does the decoder decode it with a certain clock: one picture
every 40ms? If yes, we just need to set that decoder clock to 80ms. And one
key on the remote just change that clock, the other code in VDR can remain
unchanged. Let me take some looks in the doc ...
Maybe VIDEO_SLOWMOTION can do that. From the doc:
"int ioctl(int fd, int request = VIDEO_SLOWMOTION, int nFrames);
 This ioctl call asks the Video Device to repeat decoding frames N number of
 times." 
Let the decoder play it several times, not VDR :-) But I have no
idea whether it works with play_iframe.

btw. the slowmotion command of vdr can be slower too, currently Klaus send a
"2" to the driver, higher numbers (slower replay) should possible also.

VDR have 4 replay modes: backward,  normal play, and fast (iframe only
play). This modes differ in how the data are sent to the driver. Now apply
VIDEO_SLOWMOTION with different nFrames to each of this modes, and you have
more speed levels in each mode.

M.


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