[XviD-devel] decoding without output

[Michael Militzer]

Hi,

in your example you want to fast-forward to arbitrary frames in the
stream and not just search keyframe by keyframe. In this case, the frame
you intend to jump to can have dependencies on all previous frames since
the past keyframe.

Therefore, to decode and display such arbitrary frame all frames starting
from the most recent keyframe need be parsed (and fully reconstructed). It
is theoretically possible to skip the reconstruction part of B-frames that
are not supposed to be displayed but this option is not yet implemented
in the Xvid decoder.

What you can do is to make sure that the decoder does not perform any
unneeded tasks on frames you won't display. So you should make sure that
no colorspace conversion is performed on such frames (use XVID_CSP_INTERNAL)
and that postprocessing is disabled.

Regards,
Michael


Quoting Stephan Assmus <superstippi at gmx.de>:

> Hi all,
>
> is there a way to decode the stream in order to advance the decoder state
> to a certain picture as fast as possible while skipping any decoding steps
> not necessary for that? I want to know this for seeking. Assuming this
> situation:
>
>      Keyframe A                            Keyframe B
> .....|.....................................|..............
>            *1                    *2
>
> I have decoded and displayed all frames since keyframe A until position 1.
> Now I want to get to position 2 as fast as possible without displaying
> anything. So anything that the decoder would do to display pictures can be
> skipped, while anything it needs to do and keep track of to finally start
> outputting frames again from position 2 should be done.
>
> Can I put the decoder into such a "fast forward" mode?
>
> Best regards,
> -Stephan
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>