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• How to read short (16bits) integers from an unsigned char (8bits) buffer

  28 août 2013, par Alba Malaga

  As in the title I need to read short integers from a char buffer

  The buffer

  uint8_t *data[AV_NUM_DATA_POINTERS]

  which is a field of the AVFrame frame structure, is filled by a call to the ffmpeg function

  avcodec_decode_audio4(avctx,frame,got_frame_ptr,avpkt)

  But, I need to read this buffer as a buffer of signed 16 bits integers because this is the sample format indicated by the codec context
  avctx->sample_fmt==AV_SAMPLE_FMT_S16

  I tried to do this using a memcpy but I have not succeeded to get reasonable values so then I tried to use a union struct as suggested on some related questions here in StackOverflow. My code is as follows :
  union CharToStruct
  uint8_t myCharArray[2] ;
  short value ;
  presentSound ;

   audioRet=avcodec_decode_audio4(avctx,frame,got_frame_ptr,avpkt);
  
   if(got_frame_ptr){
  
       audioRet=audioRet/2;
  
       int b=0;
  
       for(int i=0;idata[0][2*i+1];
  
           presentSound.myCharArray[1]=frame->data[0][2*i]
  
           dbuf[((i-b)/2)*8+inc-è>mLeft+b]=info->presentSound.value;//the reason of the offset by 8 here is because I will be writing the result to a multichannel device
  
   }

  With this, the values are reasonable, but when I write this to a device using portaudio, I get just clicking noise. Am I doing the conversion in a wrong way ? Can you help me maybe with some better way to do this reading ?

  Thank you very much for your help

  Alba

• Issue with ffmpeg ubuntu

  12 octobre 2017, par Rahul Agnihotri

  I am getting below given error while trying to use ffmpeg :

  video:45kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead : unknown

  The command i am executing is as follows :
  sudo ffmpeg -i /home/agnihotri/Downloads/1.mp4 -vf fps=1/600 /home/agnihotri/positive/img%03d.jpg

  My objective to extract or save a image every 10 seconds...however it only works for initial 30 seconds and then gives the error or issue.

  Thanks in advance.

  Rahul Agnihotri

• 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.