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• Can OpenCV decode H264 - MPEG-4 AVC (part 10)

  15 avril 2015, par Sergiy

  I am trying to use OpenCV (python bindings) to connect to a UDP multicast and recover individual received frames for post-processing.

  I can connect to my multicast via VLC, and VLC displays the broadcast with no issues at all. VLC reports that the codec it uses for decoding is H264 - MPEG-4 AVC (part 10).

  When I try to decode using OpenCV, I do see my video stream, but many frames appear fragmented. The frames appear as if the last line of pixels just got repeated to fill in the rest of the image (sometimes 75% or more of the whole image). OpenCV reports decoding errors (error while decoding MB ...., bytestream ).

  Is there any way to force OpenCV to use whatever codec VLC is using ? I tried to specify the specific codec to use in my code for OpenCV but it seems to have no effect.

  The code I am using is below :

  import numpy as np
  
  import cv2
  
  from cv2 import cv
  
  
  
  cap = cv2.VideoCapture()
  
  cap.set(cv.CV_CAP_PROP_FOURCC, cv.CV_FOURCC('A','V','C','1')) 
  
  cwi=cap.open(r'myurlandport')
  
  
  
  counter = 0
  
  
  
  while(cap.isOpened()):
  
  
  
      ret, frame = cap.read()
  
  
  
  
  
      counter += 1
  
  
  
      if counter % 30 == 0:
  
          cv2.imshow('frame', frame)
  
          if cv2.waitKey(1) & 0xFF == ord('q'):
  
              break
  
  
  
  cap.release()
  
  cv2.destroyAllWindows()

• How to add the timestamp as a part of the generated image file name in ffmpeg

  2 novembre 2015, par Sen

  I am trying to extract png images from a video using ffmpeg and add the timestamp as a part of the generated image file name.

  Please see the below command I am using for the same

  ffmpeg -vcodec mpeg2video -f mpegts -i test_movie.ts -f image2 -vf "drawtext=fontfile=/Library/Fonts/Tahoma.ttf: timecode='$(date +%H\\:%M\\:%S).00': r=30: x=(w-tw)/2: y=h-(2*lh): fontcolor=white: box=1: boxcolor=0x00000000@1" -vsync vfr -pattern_type glob ./compare_multiple_$(gdate +%H\_%M\_%S_%3N).png

  But this is not appending the filename properly. It gives an error as shown below :

  [image2 @ 0x7ff01301f600] Could not get frame filename number 2 from
  pattern ’./compare_multiple_10_09_58_490.png’ (either set updatefirst
  or use a pattern like %03d within the filename pattern)
  av_interleaved_write_frame() : Invalid argument frame= 10 fps=0.0
  q=-0.0 Lsize=N/A time=00:00:00.12 bitrate=N/A video:1047kB audio:0kB
  subtitle:0kB other streams:0kB global headers:0kB muxing overhead :
  unknown Conversion failed !

• avfilter/x86/vf_maskedmerge : Clear upper part of width

  23 décembre 2015, par Michael Niedermayer

  avfilter/x86/vf_maskedmerge : Clear upper part of width
  Fixes crash
  
  Fixes : Ticket5055
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavfilter/x86/vf_maskedmerge.asm