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• OpenCV VideoWriter produces "can't find starting number" error

  5 avril 2020, par user3325139

  I am trying to write 16-bit grayscale video using the FFV1 codec and opencv.ImageWriter on Windows 10

  



  Here is my code :

  



  import numpy as np
import cv2, pdb

print(cv2.getBuildInformation())

def to8(img):
    return (img/256).astype('uint8')

cap = cv2.VideoCapture(0+cv2.CAP_DSHOW)
cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('Y','1','6',' '))
cap.set(cv2.CAP_PROP_CONVERT_RGB, False)

out = cv2.VideoWriter('out.avi', cv2.VideoWriter_fourcc('F','F','V','1'), cap.get(cv2.CAP_PROP_FPS), (int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)),int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))))

while True:
    ret, frame = cap.read()
    frame = cv2.normalize(frame,None,0,65535,cv2.NORM_MINMAX)

    cv2.imshow('Video',to8(frame))
    out.write(frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break
cap.release()
out.release()
cv2.destroyAllWindows()


  



  And here is my error :

  



  [ERROR:0] global C:\projects\opencv-python\opencv\modules\videoio\src\cap.cpp (415) cv::VideoWriter::open VIDEOIO(CV_IMAGES): raised OpenCV exception:

OpenCV(4.2.0) C:\projects\opencv-python\opencv\modules\videoio\src\cap_images.cpp:253: error: (-5:Bad argument) CAP_IMAGES: can't find starting number (in the name of file): out.avi in function 'cv::icvExtractPattern'


  



  I am running this script from a command window with admin privileges. I've tried both making sure the output file does and does not exist before running.

  



  My OpenCV build information is here : https://pastebin.com/whtF6ixG

  



  Thanks !

  



  EDIT :
Based on Rotem's suggestion, instead of using VideoWriter I piped directly to FFMPEG using ffmpeg-python :

  



  import numpy as np
import cv2, pdb
import ffmpeg

def to8(img):
    return (img/256).astype('uint8')

cap = cv2.VideoCapture(0+cv2.CAP_DSHOW)
cap.set(cv2.CAP_PROP_FOURCC, cv2.VideoWriter_fourcc('Y','1','6',' '))
cap.set(cv2.CAP_PROP_CONVERT_RGB, False)

ff_proc = (
    ffmpeg
    .input('pipe:',format='rawvideo',pix_fmt='gray16le',s='%sx%s'%(int(cap.get(cv2.CAP_PROP_FRAME_WIDTH)),int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))),r='60')
    .output('out3.avi',vcodec='ffv1',an=None)
    .run_async(pipe_stdin=True)
)

while True:
    ret, frame = cap.read()

    cv2.imshow('Video',to8(frame))
    ff_proc.stdin.write(frame)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

out.terminate()
cap.release()
cv2.destroyAllWindows()


  


• libavcodec/libx264 : fix reference frame computation based on level

  16 avril 2020, par Josh Brewster

  libavcodec/libx264 : fix reference frame computation based on level
  The current implementation allows passing levels to libavcodec as
  
  integers (such as "31" instead of "3.1").
  However, in this case, the maximum reference frame value per level was
  
  ignored because libavcodec converted the string to 310 instead of 31.
  Since libx264 has correctly parsed the level to int
  
  (x4->params.i_level_idc), we should rely on this value instead of
  
  attempting to parse the level string on our own.
  Signed-off-by : Josh Brewster <josh.brewster@protonmail.com>
  
  Signed-off-by : Josh de Kock <josh@itanimul.li>
  

  • [DH] libavcodec/libx264.c

• avformat/matroskaenc : Move adding SeekEntry into end_ebml_master_crc32()

  27 avril 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Move adding SeekEntry into end_ebml_master_crc32()
  Up until now, SeekEntries were already added before
  
  start_ebml_master_crc32() was even called and before we were actually
  
  sure that we really write the element the SeekHead references : After
  
  all, we might also error out later ; and given that the allocations
  
  implicit in dynamic buffers should be checked, end_ebml_master_crc32()
  
  will eventually have to return errors itself, so that it is the right
  
  place to add SeekHead entries.
  The earlier behaviour is of course a remnant of the time in which
  
  start_ebml_master_crc32() really did output something, so that the
  
  position before start_ebml_master_crc32() needed to be recorded.
  
  Erroring out later is also not as dangerous as it seems because in
  
  this case no SeekHead will be written (if it happened when writing
  
  the header, the whole muxing process would abort ; if it happened
  
  when writing the trailer (when writing chapters not available initially),
  
  writing the trailer would be aborted and no SeekHead containing the
  
  bogus chapter entry would be written).
  This commit does not change the way the SeekEntries are added for those
  
  elements that are output preliminarily ; this is so because the SeekHead
  
  is written before those elements are finally output and doing it
  
  otherwise would increase the amount of seeks.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c