Im either being particularly stupid today or this is not a
sufficient explanation for me to fully understand.
How is continuous different from "continuously incrementing the
frame counter?"
When I hit play in quicktime I imagine someplace there is a
timer. This timer looks at the QTUnit timebase and figures out how
often it has to decompress the audio/video/timecode etc track. (right?)
Are you saying the asynchronous playback will pre-fetch or
pre-decompress outside of the timer ? like some sort of thread analogy,
and pre-store the decoded frames in ram to be fed to QT Player when the
timer indicates that said frame is needed? And that this is more
efficient because its outside of some main run loop or something?
Obviously by manually incrementing the playhead one cant do
this (meaning the pre-fetching)? So is the timebase 'just in time'
decoding? and this is what QC does?
Is this what you mean by asynchronous vs time based?
Forgive me for being .. um. dense (long day). Feel free to speak
to me like im 5 years old (no, im serious, I really am curious and dont
mind if you feel like you are patronizing me or anything - id rather
know).
Just curious - although ive got the feeling Ive answered my own
question here.
Ive cc'ed the QC list for their amusement.
On Jul 13, 2007, at 7:49 PM, Pierre-Olivier Latour wrote:
Here's an analogy: open a movie in QT
Player, then play it:
1 - either by press right arrow key
repetitively, or dragging the playhead, etc...
2 - either by pressing play
QC does #1 for reasons explained before
and for some codecs, some movie sizes and a whole bunch of factors,
this may not be as efficient as #2
On Jul 13, 2007, at 4:40 PM, Roger Bolton
wrote:
On 14 Jul 2007, at 00:31,
Pierre-Olivier Latour wrote:
There's no doc that I know of or
anything: it's just common sense: if the movie is stepped
frame-by-frame like QC does because it tracks the patch time, it's just
less efficient as playing it straight in a "continuous" way which
allows pre-fetching of the data, async decompression and whatnot.
I'm not really understanding you here. Quicktime also tracks timecode
and plays frame by frame, otherwise it would play faster than realtime
and lose sync. The whole
point of quicktime is that a 25 fps clip will never play faster than
25fps. Quicktime also
needs to keep multiple tracks in sync, eg quicktime can have more than
one audio track, so it has to have its own internal counter which is
telling it when to play each frame.
How is this different to the way that QC handles it?
From my own experience QC can play back
HD in realtime and efficiently, I don't really see a performance
difference between QC and QT player.
Roger
CoreMelt
v
a d e //
abstrakt.vade.info
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