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• lavc : Use hardware config information in ff_get_format()

  26 octobre 2017, par Mark Thompson

  lavc : Use hardware config information in ff_get_format()
  This removes the dependency that hardware pixel formats previously had on
  
  AVHWAccel instances, meaning only those which actually do something need
  
  exist after this patch.
  Also updates avcodec_default_get_format() to be able to choose hardware
  
  formats if either a matching device has been supplied or no additional
  
  external configuration is required, and avcodec_get_hw_frames_parameters()
  
  to use the hardware config rather than searching the old hwaccel list.
  

  • [DBH] libavcodec/decode.c
  • [DBH] libavcodec/internal.h

• bash Shell : lost first element data partially

  10 mars 2016, par Sandeep Singh Rana

  Using bash shell :
  I am trying to read a file line by line.
  and every line contains two meaning full file names delimited by "``"

  file:1 image_config.txt

  bbbbb.mp4``thumb/hashdata.gif
  
  bbbbb.mp4``thumb/hashdata2.gif

  Shell Script

  #!/bin/bash
  
  filename="image_config.txt"
  
  
  
  while IFS='' read -r line || [[ -n "$line" ]]; do
  
  
  
  IFS='``' read -r -a array <<< "$line"
  
  if [ "$line" = "" ]; then
  
  echo lineempty
  
  else
  
  
  
  file=${array[0]}
  
  hash=${array[2]}
  
  
  
      echo $file$hash;
  
      output=$(ffmpeg -v warning -ss 2 -t 0.8 -i $file -vf scale=200:-1 -gifflags +transdiff -y $hash);
  
      echo $output;
  
  #    echo ${array[0]}${array[1]}${array[2]}
  
  fi;
  
  
  
  done < "$filename"

  first time executed successfully but when loop executes second time.
  variable file lost bbbbb from bbbbb.mp4
  and following output comes out

  Output :

  user@domain [~/public_html/Videos]$ sh imager.sh 
  
  bbbbb.mp4thumb/hashdata.gif
  
  
  
  .mp4thumb/hashdata2.gif
  
  .mp4: No such file or directory
  
  
  
  lineempty

• Extract frames as images from an RTMP stream in real-time

  7 novembre 2014, par SoftForge

  I am streaming short videos (4 or 5 seconds) encoded in H264 at 15 fps in VGA quality from different clients to a server using RTMP which produced an FLV file. I need to analyse the frames from the video as images as soon as possible so I need the frames to be written as PNG images as they are received.

  Currently I use Wowza to receive the streams and I have tried using the transcoder API to access the individual frames and write them to PNGs. This partially works but there is about a second delay before the transcoder starts processing and when the stream ends Wowza flushes its buffers causing the last second not to get transcoded meaning I can lose the last 25% of the video frames. I have tried to find a workaround but Wowza say that it is not possible to prevent the buffer getting flushed. It is also not the ideal solution because there is a 1 second delay before I start getting frames and I have to re-encode the video when using the transcoder which is computationally expensive and unnecessarily for my needs.

  I have also tried piping a video in real-time to FFmpeg and getting it to produce the PNG images but unfortunately it waits until it receives the entire video before producing the PNG frames.

  How can I extract all of the frames from the stream as close to real-time as possible ? I don’t mind what language or technology is used as long as it can run on a Linux server. I would be happy to use FFmpeg if I can find a way to get it to write the images while it is still receiving the video or even Wowza if I can find a way not to lose frames and not to re-encode.

  Thanks for any help or suggestions.