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• avcodec/apng : Dispose previous frame properly

  7 juin 2015, par Donny Yang

  avcodec/apng : Dispose previous frame properly
  The spec specifies the dispose operation as how the current (i.e., currently
  
  being rendered) frame should be disposed when the next frame is blended onto it
  This is contrary to ffmpeg’s current behaviour of interpreting the dispose
  
  operation as how the previous (i.e., already rendered) frame should be disposed
  This patch fixes ffmpeg’s behaviour to match those of the spec, which involved
  
  a rewrite of the blending function
  Signed-off-by : Donny Yang <work@kota.moe>
  
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/pngdec.c

• ffmpeg C API (libswscale) : Scale a frame into an output frame with given width/height preserving aspect ratio, fill out the rest with transparency

  12 juin 2015, par nik4emniy

  Note : I need to use ffmpeg’s C API in my project.
  Input : video(let’s say,first frame)/image, output_width, output_height
  Output : PNG image with output_width/output_height.

  What I’ve done so far :

  a) decoded a frame from input into frame1

  b) sws_scale frame1 with needed context (output_width, output_height) into frame2

  c) initialized AVCodec CODEC_ID_PNG

  d) encoded frame2 into initialized AVPacket

  e) wrote AVPacket’s data into file

  So I have a working cycle that produces a PNG image, but it doesn’t save the aspect ratio (obviously).
  What I want to achieve is do the same thing preserving aspect ratio (which would change the frame2’s width||height), but then "centring" that image and filling out the "empty" parts with tranparent layer in the final PNG.

  Does anyone have an idea on how this can be achieved ?
  Again, I need to use C API, not command line.

• nested loop in bash shell

  17 juin 2015, par Tareq Suheimat

  I want to stream video using ffserver and then receive and download it using ffmpeg but first I want to add some noise to the link using netem and the wanted noise will be Bit error,so for the transmitter side there’s no problem the problem is at the receiver side
  so the first loop must contain the percentage numbers of the bit error like 0.2 0.4 0.6 0.8 and do the following command :

  tc qdisc change dev eth0 root netem corrupt 0.1%

  then for each one of the bit error values must repeat it for 10 times and for each try I must download the received video using the following command :

  ffmpeg -i rtsp://localhost:7654/test1-rtsp.mpg -acodec copy -vcodec copy output.mp4 

  so later I end up with too many videos to compare them later.

  please people help me it’s urgent !!!

  tell now I have this scratched code but I don’t know how to compile it together

  for i in {0.2 0.4 0.6 0.8}
  
  do
  
      tc qdisc change dev eth0 root netem corrupt ${i}%
  
  
  
      #(must repeat for each i the ffmpeg download command 10 times)
  
  
  
      #The download command
  
      for x in {1..N}
  
      do
  
          ffmpeg -i rtsp://localhost:7654/test-rtsp.mpg -acodec copy -vcodec copy tested${x}.mp4
  
      done