belcampo wrote:
Oliver Seitz wrote:
My feeling is that the full frame caching is certainly more general and
probably easier to implement, and would mean consistent behaviour
regardless of source. People will scream about the massive memory
footprint, but it seems like a reasonable application of RAM to me.
I've thought about that, but the method lacks of inflexibility. You then
can only step back to frames you've recently played. I think if there
is a
feature for stepping back one frame it should do that, regardless if the
part was played before. If the cache of decoded frames has to be extended
backwards you get almost the behavior of VirtualDub, just a bit more
complex and memory consuming.
I am quite unfamiliar with video file formats. Is it true that frames are
accessed via some sort of "linked list" and is therefore difficult to
find
the start of a certain frame? Implementing a cache storing the entry
points of every frame may help. If not the file position but the
length of
each frame is stored, 32bit should suffice. 1MB of cache would hold
enough
frame lengths for 2.5 hours of video. This "extended index" could be
generated on request by command line switch.
Sorry, I'm dreaming ;-)
AAASSSS FFFFAAAAAARRRRRR AAAAAASSSSS IIIIIII KKKKKNNNNNOOOOOOWWWWWW !!!
I-Frames/Key-Frames are 'a whole picture' following frames are more or
less 'former-frame plus/minus the difference'.
following frames are calculated from those origin and differences. So
stepping forward is rather simple, it is 'normal'play at non-standard
speed.
Going back is difficult in the sense you have to calculate several
frames plus/minus the differences to 'know' how that former frame has
looked.
Greets,
Kiste
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In PAL-land we have I-frame/Key-frame every 12th frame. The max you need
to enable back-stepping is the info of 12frames at DVD-quality that
needs ((9000kb/25)*12)/8 about .54MB of memory. There will some more for
overhead but you won't need that much "I think".
PS. I only have a small head with no so much brains in it.
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