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• avcodec : Fix invalid uses of ff_codec_open2_recursive()

  26 novembre 2020, par Andreas Rheinhardt

  avcodec : Fix invalid uses of ff_codec_open2_recursive()
  Normally no two codecs with FF_CODEC_CAP_INIT_THREADSAFE unset
  
  can be initialized at the same time : a mutex in avcodec_open2()
  
  ensures this. This implies that one cannot simply open a codec
  
  with a non-threadsafe init-function from the init function of
  
  a codec whose own init function is not threadsafe either as the child
  
  codec couldn't acquire the lock.
  ff_codec_open2_recursive() exists to get around this limitation :
  
  If the init function of the child codec to be initialized is not
  
  thread-safe, the mutex is unlocked, the child is initialized and
  
  the mutex is locked again. This of course has as a prerequisite that
  
  the parent AVCodecContext actually holds the lock, i.e. that the
  
  parent codec's init function is not thread-safe. If it is, then one
  
  can (and has to) just use avcodec_open2() directly (if the child's
  
  init function is not thread-safe, then avcodec_open2() will have to
  
  acquire the mutex itself (and potentially wait for it), so that it is
  
  perfectly fine for an otherwise thread-safe init function to open
  
  a codec with a potentially non-thread-safe init function via
  
  avcodec_open2()).
  Yet several of the users of ff_codec_open2_recursive() have the
  
  FF_CODEC_CAP_INIT_THREADSAFE flag set ; this only worked because
  
  all the child codecs' init functions were thread-safe themselves
  
  so that ff_codec_open2_recursive() didn't touch the mutex at all.
  
  But of course the real solution to this is to directly use
  
  avcodec_open2().
  Reviewed-by : Anton Khirnov <anton@khirnov.net>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/avrndec.c
  • [DH] libavcodec/imm5.c
  • [DH] libavcodec/tdsc.c

• What these FFmpeg APNG encoder prediction methods mean ?

  14 septembre 2021, par Nicke Manarin

  By typing ffmpeg -h encoder=apng, I get this :

  


  APNG encoder AVOptions:&#xA;  -dpi               <int>        E..V..... Set image resolution (in dots per inch) (from 0 to 65536) (default 0)&#xA;  -dpm               <int>        E..V..... Set image resolution (in dots per meter) (from 0 to 65536) (default 0)&#xA;  -pred              <int>        E..V..... Prediction method (from 0 to 5) (default none)&#xA;     none                         E..V.....&#xA;     sub                          E..V.....&#xA;     up                           E..V.....&#xA;     avg                          E..V.....&#xA;     paeth                        E..V.....&#xA;     mixed                        E..V.....&#xA;</int></int></int>

  


  What are the differences among these prediction methods ?

  


  I could not find any documentation on ffmpeg.org or anywhere else.

  


• Send a file and parameters to a OpenFaas Dockerfile function

  29 juillet 2021, par Johannes Klauß

  I have a ffmpeg Dockerfile function that I deploy to my OpenFaaS :

  


  FROM ghcr.io/openfaas/classic-watchdog:0.1.5 as watchdog

FROM jrottenberg/ffmpeg:4.1-alpine

RUN mkdir -p /home/app

COPY --from=watchdog /fwatchdog /usr/bin/fwatchdog
RUN chmod +x /usr/bin/fwatchdog

# Add non root user
RUN addgroup -S app && adduser app -S -G app
RUN chown app /home/app

WORKDIR /home/app

USER app

# Populate example here - i.e. "cat", "sha512sum" or "node index.js"
ENV fprocess="ffmpeg"
# Set to true to see request in function logs
ENV write_debug="false"

EXPOSE 8080

HEALTHCHECK --interval=3s CMD [ -e /tmp/.lock ] || exit 1

CMD ["fwatchdog"]


  


  But I cannot figure out how I would be able to stream a file to the function and give parameters, so that ffmpeg knows about the file and parameter.
I am fairly new to OpenFaaS and maybe this is trivial, but I cannot wrap my head around it.

  


  Any help would be much appreciated.