[FFmpeg-user] videodetect filter? - equivalent to:https://ffmpeg.org/ffmpeg-filters.html#silencedetect

[Paul B Mahol]

On 4/10/16, Mark Hassman <mark at hassman.org> wrote:
>
>> -----Original Message-----
>> From: ffmpeg-user [mailto:ffmpeg-user-bounces at ffmpeg.org] On
>> Behalf Of Paul B Mahol
>> Sent: Sunday, April 03, 2016 11:42 AM
>> To: FFmpeg user questions
>> Subject: Re: [FFmpeg-user] videodetect filter? - equivalent
>> to:https://ffmpeg.org/ffmpeg-filters.html#silencedetect
>>
>> On 4/3/16, Moritz Barsnick <barsnick at gmx.net> wrote:
>> > On Sat, Apr 02, 2016 at 17:02:19 -0400, Mark Hassman wrote:
>> >> Any chance someone knows a set of filters to accomplish the same
>> >> thing for video as:
>> https://ffmpeg.org/ffmpeg-filters.html#silencedetect.. i.e.
>> >> timestamps output for start/end of motion.
>> >
>> > While silence would be more like darkness in video ;-) I
>> get what you
>> > mean:
>> >
>> >> I've looked at:
>> >> http://www.lavrsen.dk/foswiki/bin/view/Motion/WebHome, but already
>> >> transcoding with ffmpeg - hoping to add a simple filter to
>> accomplish the same.
>> >
>> > I too am looking for a filter which can at least imitate simple
>> > features of the tool "motion", as motion only does
>> real-time detection
>> > from input devices. This would mean replicating "motion"'s
>> algorithms
>> > in a filter, or using existing filters.
>> >
>> > I once tried, and had come to the conclusion - from reading
>> the docs -
>> > that the decimate filter might be close to the right thing.
>> While the
>> > docs mention "regular intervals", which wouldn't be
>> appropriate, they
>> > also speak of "threshold for duplicate detection" and "detection of
>> > [small] movements". I have never gotten the decimate filter to work
>> > for anything I needed it for though, which went beyond
>> motion detection.
>> >
>> > For anyone willing to help out, here are the main chaacteristics of
>> > "motion"'s features, some of which may not be feasible
>> within ffmpeg:
>> > - Detection of motion by observing the number of changed pixels from
>> >   one frame to the next, and passing this detected frame on to the
>> >   output. (This could be a percentage or a mean square deviation
>> >   instead, but "motion" doesn't support that.)
>> > - Retaining a configurable amount of images before and after the
>> >   detected event.
>> > - Optionally visually marking the section of the video
>> where the change
>> >   was detected. (This could be in frame metadata instead,
>> but "motion"
>> >   doesn't support that.)
>> >
>> > At least the first point would be nice to have, but I'd rather not
>> > implement such a filter which reinvents the wheel.
>> >
>> > In other words: I too would appreciate a hint as how to use
>> ffmpeg's
>> > filters to achieve this.
>>
>> See singnalstats filter.
>
>
> Thanks for the advice!
>
> Using signalstats YDIF, I'm able to derive what I need. However, I'm unable
> to get the data out of ffmpeg for parsing/eventing.
>
> The drawtext filter has access to all the set_meta values
> (https://ffmpeg.org/pipermail/ffmpeg-cvslog/2014-June/078245.html) -
> injecting the relevant data via graphical overlay works as expected, but I
> can't find a way to push into stdout or ascii file.
>
> Unsuccessfully, i've been looking for another filter capable of accessing
> ffmpeg's internal meta tags to accomplish this. The closest i've found is
> showinfo, but i can't specify which meta tags to use.
>
> I've also tried the scene filter, but it modifies the video - i need only
> reporting.
>
> Note: I'm using ffmpeg - not ffprobe as this is a live encode.. ffmpeg
> doesn't support -show_entries/frame_tags. Is there any way to effectively
> reproduce this with ffmpeg?
>

ffprobe or with ffmpeg and metadata filter.

>
> Does anyone have ideas on this?
> Thanks in advance!
>
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