[FFmpeg-devel] [PATCH v1] avfilter/vf_freezedetect: add metadata lavfi.freezedetect.mafd

[Limin Wang]

On Wed, Oct 23, 2019 at 02:32:54PM +0200, Marton Balint wrote:
> 
> 
> On Wed, 23 Oct 2019, Limin Wang wrote:
> 
> >
> >
> >ping, it's another approach to discard frozen frame, please comments.
> >
> >
> >On Thu, Oct 10, 2019 at 11:48:40AM +0800, lance.lmwang at gmail.com wrote:
> >>From: Limin Wang <lance.lmwang at gmail.com>
> >>
> >>As suggested by Paul to support frozen frames discard, please refer to:
> >>https://patchwork.ffmpeg.org/patch/15423/
> >>
> >>You can tested with below commands:
> >>
> >>./ffmpeg  -f lavfi -i "smptebars=duration=5:size=1280x720:rate=30,freezedetect,metadata=mode=select:key=lavfi.freezedetect.mafd:value=0.01:function=greater"  -f null -
> >>frame=    1 fps=0.0 q=-0.0 Lsize=N/A time=00:00:00.03 bitrate=N/A speed=2.14x
> >>
> >>Signed-off-by: Limin Wang <lance.lmwang at gmail.com>
> >>---
> >> doc/filters.texi              | 9 +++++++++
> >> libavfilter/vf_freezedetect.c | 7 +++++++
> >> 2 files changed, 16 insertions(+)
> >>
> >>diff --git a/doc/filters.texi b/doc/filters.texi
> >>index 55a8ebae56..cfc10c8479 100644
> >>--- a/doc/filters.texi
> >>+++ b/doc/filters.texi
> >>@@ -10800,6 +10800,15 @@ timestamp of the first frame of the freeze. The
> >> @code{lavfi.freezedetect.freeze_end} metadata keys are set on the first frame
> >> after the freeze.
> >>
> >>+The @code{lavfi.freezedetect.mafd} metadata key is set for all frames except the
> >>+first reference frame. You can use it to drop frozen frames by metadata select
> >>+mode. Note that in this way the first few frozen frames(the detection interval)
> >>+are dropped also. An example is as follows:
> >>+ at example
> >>+freezedetect,metadata=mode=select:key=lavfi.freezedetect.mafd:value=0.001:function=greater
> >>+ at end example
> 
> No, this is not what this is. This way you drop in the detection
> interval even if no freeze is detected. So this approach is only
> slightly different to selecting a very small (less than a frame)
> detection interval.

If one frame is detected as frozen frame, it'll be dropped. The freezedetect.mafd will be
the mafd between the next frame with the first frozen frame, if it's frozen frame(<threeshold),
still, it'll be continued drop. So we may think it's not frozen frame if only one frame mafd
less than the threshold, so you need set the threshold very small to avoid misdetecting.
With detection interval, you can't avoid misdetect still if the threshold isn't good choose.


> 
> So I don't see the point of this patch.
> 
> Regards,
> Marton
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