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• avconv : from multiple png to movie not exporting correctly

  13 avril 2016, par abhra

  I am trying to generate a mp4 movie from a set of pngs using avconv on my debian8 system. The mp4 file its generating basically looping over the first figure for some time. Here is the command I am using

  avconv -r 10 -start_number 8 -i images_%06d.png -b:v 1000k -vf scale=640 :-1 test.mp4

  Output is

  avconv version 11.6-6:11.6-1 deb8u1, Copyright (c) 2000-2014 the Libav developers built on Mar 2 2016 23:00:02 with gcc 4.9.2
  (Debian 4.9.2-10) Input #0, image2, from ’images_%06d.png’ :
  Duration : 00:00:16.00, start : 0.000000, bitrate : N/A
  Stream #0.0 : Video : png, rgb24, 2400x1801, 25 fps, 25 tbn File ’test.mp4’ already exists. Overwrite ? [y/N] y [scale @ 0x820c60] The
  ::flags= option syntax is deprecated. Use either
  : : or w=:h=:flags=. [libx264 @ 0x837760]
  using cpu capabilities : MMX2 SSE2Fast SSSE3 SSE4.2 AVX AVX2 FMA3 LZCNT
  BMI2 [libx264 @ 0x837760] profile High, level 2.2 [libx264 @ 0x837760]
  264 - core 142 r2431 a5831aa - H.264/MPEG-4 AVC codec - Copyleft
  2003-2014 - http://www.videolan.org/x264.html - options : cabac=1 ref=3
  deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00
  mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0
  deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=12
  lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0
  bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1
  b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250
  keyint_min=10 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr
  mbtree=1 bitrate=1000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4
  ip_ratio=1.40 aq=1:1.00 Output #0, mp4, to ’test.mp4’ : Metadata :
  encoder : Lavf56.1.0
  Stream #0.0 : Video : libx264, yuv420p, 640x480, q=-1—1, 1000 kb/s, 10 fps, 10 tbn, 10 tbc
  Metadata :
  encoder : Lavc56.1.0 libx264 Stream mapping : Stream #0:0 -> #0:0 (png (native) -> h264 (libx264)) Press ctrl-c to stop encoding frame= 17 fps= 0 q=0.0 size= 0kB time=10000000000.00
  bitrate= 0.0kbitframe= 34 fps= 32 q=0.0 size= 0kB
  time=10000000000.00 bitrate= 0.0kbitframe= 51 fps= 32 q=0.0 size=
  0kB time=10000000000.00 bitrate= 0.0kbitframe= 393 fps= 32 q=0.0
  Lsize= 139kB time=39.00 bitrate= 29.2kbits/s video:132kB
  audio:0kB other streams:0kB global headers:0kB muxing overhead :
  5.284794% [libx264 @ 0x837760] frame I:2 Avg QP : 3.69 size : 51320 [libx264 @ 0x837760] frame P:99 Avg QP : 0.32 size : 242 [libx264
  @ 0x837760] frame B:292 Avg QP : 0.15 size : 26 [libx264 @
  0x837760] consecutive B-frames : 0.8% 0.5% 0.0% 98.7% [libx264 @
  0x837760] mb I I16..4 : 45.5% 19.2% 35.3% [libx264 @ 0x837760] mb P
  I16..4 : 0.0% 0.0% 0.0% P16..4 : 0.9% 0.0% 0.0% 0.0% 0.0%
  skip:99.0% [libx264 @ 0x837760] mb B I16..4 : 0.0% 0.0% 0.0%
  B16..8 : 0.2% 0.0% 0.0% direct : 0.0% skip:99.8% L0:22.3% L1:77.7%
  BI : 0.0% [libx264 @ 0x837760] final ratefactor : -21.09 [libx264 @
  0x837760] 8x8 transform intra:18.9% inter:41.7% [libx264 @ 0x837760]
  coded y,uvDC,uvAC intra : 34.1% 0.0% 0.0% inter : 0.1% 0.0% 0.0%
  [libx264 @ 0x837760] i16 v,h,dc,p : 81% 14% 5% 0% [libx264 @
  0x837760] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu : 49% 14% 36% 0% 0% 0% 0%
  0% 0% [libx264 @ 0x837760] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu : 36% 28% 19%
  3% 3% 2% 4% 2% 3% [libx264 @ 0x837760] i8c dc,h,v,p : 100% 0% 0%
  0% [libx264 @ 0x837760] Weighted P-Frames : Y:0.0% UV:0.0% [libx264 @
  0x837760] ref P L0 : 99.3% 0.0% 0.6% 0.1% [libx264 @ 0x837760] ref B
  L0 : 4.2% 95.8% [libx264 @ 0x837760] ref B L1 : 99.8% 0.2% [libx264 @
  0x837760] kb/s:27.34

  I have also tried

  cat *.png | avconv -f image2pipe -i - -b:v 1000k -vf scale=640 :-1 test2.mp4

  output shows

  avconv version 11.6-6:11.6-1 deb8u1, Copyright (c) 2000-2014 the Libav developers built on Mar 2 2016 23:00:02 with gcc 4.9.2
  (Debian 4.9.2-10) Codec AVOption b (set bitrate (in bits/s)) specified
  for output file #0 (test2.mp4) has not been used for any stream. The
  most likely reason is either wrong type (e.g. a video option with no
  video streams) or that it is a private option of some encoder which
  was not actually used for any stream. Output #0, image2pipe, to
  ’test2.mp4’ : Output file #0 does not contain any stream

  When getting frames fromtest.mp4

  avconv -i test.mp4 -r 30 -f image2 %04d.png

  I found 1000 or more copies of the images_000001.png.

  Would you please help, whether I have made any mistake in commands ? Or am I missing some codec options ? Thanks for the help.

• JavaCV grab frame method delays and returns old frames

  27 janvier 2019, par Null Pointer

  I’m trying to create a video player in Java using JavaCV and its FFmpegFrameGrabber class. Simply, Inside a loop, I use

  .grab() to get a frame and then paint it on a panel

  Problem is, player gets delayed. For example, after 30 seconds passes, in video only 20 seconds passes.

  Source is ok. Other players can play the stream normally. Problem is possibly the long printing time.

  What I do not understand is that : "why does .grab() method brings me a frame from 10 seconds ago ?" Shouldn’t it just grab the frame which is being streamed at the moment ?

  (Sorry for not providing a working code, it’s all over different huge classes)

  I use the following grabber options (selected by some other colleague) :

  grabber.setImageHeight(480);
  
  grabber.setImageWidth(640);
  
  grabber.setOption("reconnect", "1");
  
  grabber.setOption("reconnect_at_eof", "1");
  
  grabber.setOption("reconnect_streamed", "1");
  
  grabber.setOption("reconnect_delay_max", "2");
  
  grabber.setOption("preset", "veryfast");
  
  grabber.setOption("probesize", "192");
  
  grabber.setOption("tune", "zerolatency");
  
  grabber.setFrameRate(30.0);
  
  grabber.setOption("buffer_size", "" + this.bufferSize);
  
  grabber.setOption("max_delay", "500000");
  
  grabber.setOption("stimeout", String.valueOf(6000000));
  
  grabber.setOption("loglevel", "quiet");
  
  grabber.start();

  Thanks

• OpenCV returns an Empty Frame on video.read

  20 mars 2019, par Ikechukwu Anude

  Below is the relevant code

  import cv2 as cv
  
  import numpy as np
  
  
  
  video = cv.VideoCapture(0) #tells obj to use built in camera\
  
  
  
  #create a face cascade object 
  
  face_cascade  = 
  
  cv.CascadeClassifier(r"C:\Users\xxxxxxx\AppData\Roaming\Python\Python36\site- 
  
  packages\cv2\data\haarcascade_frontalcatface.xml")
  
  
  
  a = 1
  
  #create loop to display a video
  
  while True:
  
      a = a + 1
  
      check, frame = video.read()
  
      print(frame)
  
  
  
      #converts to a gray scale img
  
      gray = cv.cvtColor(frame, cv.COLOR_BGR2GRAY)
  
  
  
      #create the faces
  
      faces = face_cascade.detectMultiScale(gray, scaleFactor=1.5, minNeighbors=5)
  
  
  
      for(x, y, w, h) in faces:
  
          print(x, y, w, h)
  
  
  
      #show the image
  
      cv.imshow('capturing', gray)
  
  
  
      key = cv.waitKey(1) #gen a new frame every 1ms
  
  
  
      if key == ord('q'): #once you enter 'q' the loop will be exited
  
          break
  
  
  
  print(a) #this will print the number of frames
  
  
  
  #captures the first frame
  
  video.release() #end the web cam
  
  
  
  #destroys the windows when you are not defined
  
  cv.destroyAllWindows()

  The code displays a video captured from my webcam camera. Despite that, OpevCV doesn’t seem to be processing any frames as all the frames look like this

   [[0 0 0]
  
    [0 0 0]
  
    [0 0 0]
  
    ...
  
    [0 0 0]
  
    [0 0 0]
  
    [0 0 0]]]

  which I assume means that they are empty.

  This I believe is preventing the algorithm from being able to detect my face in the frame. I have a feeling that the issue lies in the ffmpeg codec, but I’m not entirely sure how to proceed even if that is the case.

  OS : Windows 10
  Language : Python

  Why is the frame empty and how can I get OpenCV to detect my face in the frame ?