Re: [9fans] A prick into the wasps' nest ;-)

[Bruce Ellis <brucee@chunder.com>]

i get really annoyed with badly mastered dvds, let alone
crap players that are worse than VHS.  i get agitated by
a dropped frame, particularly an I frame, and will return
the DVD as faulty if it happens in the "good bits".  yeah
i have 100Hz component which does more video formats than
i have the ITUs for.  even worse are the DVDs that slip
lip-sync 'cause they are badly mastered.  when the lips
and the voice get 2 frames apart i give up.  remarkable
that i can master a DVD-R from DV - at a high bit rate and
get no such problems.  this has little to do with real-time,
but ... the reason i added edf to the ps2 inferno kernel
was so the double buffering was in sync with the retrace
and the IDCT dmas were in time for the buffer.  i think
the linux guys are still working on it and are happy with
5 fps, 'cause it's a start ...

brucee

Nigel Roles wrote:
>>factors involved.  if we assume that TV is 26 (iirc) frames/second
>>there is phosphor persistance on the the screen (let's forget about
>>LCD's) and (iirc) there's retinal persistance.  so, dropping a
>>few frames  doesn't really matter.  oh yeah, it's interleaved as well.
>>
>>they may not even be watching when the frames are dropped.
>>
> 
> 
> Even if I softly drop a few words here and there, this is still
> recognisably rubbish.
> 
> The frame rate is 25Hz for PAL, or 30Hz for NTSC (29.97 for pedants).
> SECAM is also 25 Hz.
> 
> There is some persistance (sic), but the human eye/brain
> is extremely sensitive to missing frames, or disturbed frame timing,
> so it is arguable that persistence makes a timing error worse.
> You only have to watch a someone walk across the shot on a decent
> DVD player and then compare it will your typical soft decoder on
> a Windows laptop to know that seeing all the fields at the right
> time is a really important.
> 
> Interleaving only helps reduce apparent flicker. Each field represents
> a different point in time, so missing a field, or replacing one
> with a copy of the previous one is ruinous. Swap the fields and
> everything looks furry. 100Hz TVs don't just
> display each field twice; they have a DSP in there to
> sort out the motion compensation and synthesise the missing fields.
> My 100Hz TV still screws up on fast scrolling credits (horizontal
> and vertical).
> 
> Stick to what you know, Boyd.
> Except the guns; it's really, really tedious.
> 
> 
>