[FFmpeg-devel] [CLT2018] FFmpeg at Chemnitzer Linux-Tage

Alexander Strasser eclipse7 at gmx.net
Sun Mar 18 02:35:18 EET 2018

On 2018-03-13 20:08 +0100, Thilo Borgmann wrote:
> Am 13.03.18 um 19:52 schrieb Paul B Mahol:
> > On 3/13/18, Thilo Borgmann <thilo.borgmann at mail.de> wrote:
> >> Hi,
> >>
> >>> once again, FFmpeg has been accepted for CLT 2018 in Chemnitz, Germany!
> >>> This "Chemnitzer Linux Tage" will take place on 10th and 11th of March.
> >>> You can find more details on their homepage:
> >>>
> >>> https://chemnitzer.linux-tage.de/2018/en/
> >>>
> >>> Thus once again, we will man a booth with our staff and are happily
> >>> waiting for
> >>> our users to get in touch with us! If you're a developer and want to help
> >>> us or
> >>> just want to visit and check in at our booth, please let us know.
> >>
> >> we've returned from the CLT. This year has been the 20th anniversary of the
> >> CLT - so they'd put some additional effort into it to make it even a better
> >> pleasure for all the exhibitors. Most notably in terms of an updated
> >> Saturday dinner :)
> >>
> >> We presented our usual demo using motion vector overlay to attract people
> >> and Thomas and Alexander created a very nice new demo for visualization
> >> filters, command-line expressions and video output, randomly altered. We
> >> again had a lot of users coming by and Gerion also gave a workshop on
> >> command-line based filtering.
> > 
> > Which filter where used?
> Alexander knows about the complete list, maybe he can answer to that in particular.

Demo 1:
ffmpeg -loglevel quiet -framerate 15 -video_size 640x480 -i /dev/video0 -q:v 2 -mbd 2 -g 600 -f m4v -r 8 - |
  ffplay -f m4v -loglevel quiet                \
    -flags2 +export_mvs -i -                   \
    -vf codecview=mv=pf+bf+bb:mvt=fp+bp,hflip

This is a traditional demo we show since the first time in Chemnitz.
It's totally great to get visitors to stay for a while and most often
ask a question or two.

Demo 2:
ffmpeg -stream_loop -1 -i media/Sintel.2010.720p.mkv \
  -lavfi "[0:a]showwaves=mode=line:scale=log:size=1200x240[waves] ;
          [0:v]setpts=PTS-STARTPTS,split[a][b] ; [a]histogram[hist] ;
          [b]pad=iw+256:ih+240[padded] ;
          [padded][hist]overlay=W-w:0[x] ;
          [x][waves]overlay=0:H-h" -an ...

This needed lots of fifos filters inserted in the past, but works fine
without them using recent FFmpeg.

Demo 3:
ffmpeg -re -stream_loop -1 -framerate 1/3 -start_number 1 -i media/P-%d.JPG -vf '
' -an ...

This builds on the idea of a demo Stefano once prepared for Linux-Tag
in Berlin.

It will slowly loop through a bunch of pictures applying the filters on
them. In the background I am periodically randomly turning on/off the
filters hue, noise, negate, and curves from another process using ZMQ.

It also shows the original and filtered picture side by side, so
visitors can spot the differences.

I think a lot more can be added here, the question though will be
how much value it really adds and if it would then need some other
means to mix and match those filters instead of the stupid method I
used so far.

I also planned a 4th demo, but I wasn't satisfied with the results so
I dropped it after investing a few hours.

> > From older cases, they were not enough covered, causing users asking for filters
> > which are already available.

Thilo mostly replied to this one (see below). Though if you have any
particular filters in mind, that people are often asking for, but that
are already implemented, please tell me. I will try my best to get the
word out.

OT: Thank you Paul for adding and improving so many filters. I
really appreciate your work and enjoy seeing filtering in FFmpeg
getting richer and more mature.

> Hmm.. I had not heard such comments or not to a high enough extend so that this problem has made it into my memory. Just don't forget about two aspects here, first, the complete list of filters is not what we aim to show, but to give some examples to get people talking to us and asking questions (so a question if we also have filter XY would be a good result of the demo), and second, not all filters are presentable - most people seeing the demo have untrained eyes looking at it and therefore a hardly recognizable filter might result in their thought of what the hell we are doing at all there... and that thought is to be avoided by a demo :)
> However, if you (or anyone) wants a particular thing to be included in our demos, just give that remark early enough and we will happily include it. We would like to have even more ideas next time!



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