Re: [xine-devel] demux_ts - rate calculation

[<br...@it...>]

Hi Dischi,

    From dm...@sa... Wed Oct 26 02:54:44 2005
    ...
    Bruce Janson wrote:
    >     I too had similar problems playing DVB-T streams: the rate
    > that xine assumed for the stream appeared to be (very) wrong and
    > so rendered both xine_get_pos_length() and xine_play() inaccurate.
    > Eventually, I arrived at the following two-step workaround:
    >
    >     - In the main loop of the UI thread, periodically execute
    >
    >       	xine_get_pos_length(stream, (int *)0, &xine_time, (int *)0);
    > 	gettimeofday(&actual_time, (void *)0);
    
    What happens if you play at double speed?
    ...

It turns out that xine_get_pos_length()'s inaccuracy varies
with playing speed (Perhaps you suspected that this would
be so? :-)), but calculation of the correction factor adjusts
accordingly.

    >     - Now, when we want to jump to a new location -- "p" -- in
    >       our file/stream we can execute a binary search based on
    >       the pair:
    >
    >         xine_play(stream, 0, p);
    >         xine_get_pos_length_corrected(stream, (int *)0, &xine_time, (int *)0);
    >
    >       By comparing the achieved location (returned in xine_time)
    >       with the desired location (specified in p) we can derive a
    >       second correction factor for xine_play() and finally, a new
    >       function:
    >
    >         xine_play_corrected(stream, 0, p);
    >
    > Fortunately, both of these correction factors appear to be simple
    > linear multipliers of the arguments (or results) of the primitive
    > functions so, once calculated they remain useful for the rest of
    > the stream/file.
    
    A patch would be nice. Right now, seeking in dvb-t streams is very
    wrong and seeking in mpeg streams without pck header isn't working at
    all. 
    ...

The above workaround (kludge) is implemented entirely in
a test UI frontend.  I'm not yet familiar enough with the
libxine internals to know where such a patch should go
within that library, let alone whether it would be an
appropriate solution to the problem.

Regards,
bruce.