Writing an mp4 video using python opencv

Question

I want to capture video from a webcam and save it to an mp4 file using opencv  I found example code on stackoverflow  below  that works great  The only hitch is that I m trying to save it as mp4  not avi  Part of what I don t get is that the  XVID  argument passed to the FOURCC writer is supposed to be  I think  an mp4 codec  from this link   If I change the filename to  output mp4  it tells me that the tag is invalid  so I have to believe that the XVID codec is actually making an avi file  Is this a stupid question  How do I write to an mp4    I have found links showing how to convert an avi to an mp4 after the fact but that seems inefficient  Seems like I should be able to do it during the initial write   import numpy as np import cv2  cap   cv2 VideoCapture 0     Define the codec and create VideoWriter object fourcc   cv2 cv CV FOURCC   XVID   out   cv2 VideoWriter  output avi  fourcc  20 0   640 480    while cap isOpened         ret  frame   cap read       if ret  True          frame   cv2 flip frame 0             write the flipped frame         out write frame           cv2 imshow  frame  frame          if cv2 waitKey 1   amp  0xFF    ord  q                break     else          break    Release everything if job is finished cap release   out release   cv2 destroyAllWindows

User · Answer

This worked for me   self  name   name     mp4  self  cap   VideoCapture 0  self  fourcc   VideoWriter fourcc   MP4V   self  out   VideoWriter self  name  self  fourcc  20 0   640 480

User · Answer

What worked for me was to make sure the input  frame  size is equal to output video s size  in this case   680  480      http   answers opencv org question 27902 how-to-record-video-using-opencv-and-python   Here is my working code  Mac OSX Sierra 10 12 6    cap   cv2 VideoCapture 0  cap set 3 640  cap set 4 480   fourcc   cv2 VideoWriter fourcc   MP4V   out   cv2 VideoWriter  output mp4   fourcc  20 0   640 480    while True       ret  frame   cap read       out write frame      cv2 imshow  frame   frame      c   cv2 waitKey 1      if c  amp  0xFF    ord  q            break  cap release   out release   cv2 destroyAllWindows     Note  I installed openh264 as suggested by  10SecTom but I m not sure if that was relevant to the problem   Just in case   brew install openh264

User · Answer

The problem such as OpenCV  FFMPEG  tag 0x5634504d  MP4V  is not supported with codec id 13 and format  mp4   MP4  MPEG-4 Part 14   OpenCV  FFMPEG  fallback to use tag 0x00000020         maybe that your output video size is not the same as original video  You can look over the frame size of video first

User · Answer

fourcc   cv2 VideoWriter fourcc   mp4v     mp4v  returns no errors unlike  MP4V  which is defined inside fourcc  for the error  OpenCV  FFMPEG  tag 0x5634504d  MP4V  is not supported with codec id 13 and format  mp4   MP4  MPEG-4 Part 14   OpenCV  FFMPEG  fallback to use tag 0x00000020

User · Answer

There are some things to change in your code    Change the name of your output to  output mp4   change to  mp4  I had the the same issues that people have in the comments  so I changed the fourcc to 0x7634706d  out   cv2 VideoWriter  output mp4  0x7634706d   20 0   640 480

User · Answer

just change the codec to  quot DIVX quot   This codec works with all formats  fourcc   cv2 VideoWriter fourcc   DIVX    i hope this works for you

User · Answer

This is the default code given to save a video captured by camera  import numpy as np import cv2  cap   cv2 VideoCapture 0     Define the codec and create VideoWriter object fourcc   cv2 VideoWriter fourcc   XVID   out   cv2 VideoWriter  output avi  fourcc  20 0   640 480    while cap isOpened         ret  frame   cap read       if ret  True          frame   cv2 flip frame 0             write the flipped frame         out write frame           cv2 imshow  frame  frame          if cv2 waitKey 1   amp  0xFF    ord  q                break     else          break    Release everything if job is finished cap release   out release   cv2 destroyAllWindows     For about two minutes of a clip captured that FULL HD  Using  cap   cv2 VideoCapture 0 cv2 CAP DSHOW  cap set 3 1920  cap set 4 1080  out   cv2 VideoWriter  output avi  fourcc  20 0   1920 1080     The file saved was more than 150MB  Then had to use ffmpeg to reduce the size of the file saved  between 30MB to 60MB based on the quality of the video that is required changed using crf lower the crf better the quality of the video and larger the file size generated  You can also change the format avi mp4 mkv etc  Then i found ffmpeg-python   Here a code to save numpy array of each frame as video using ffmpeg-python  import numpy as np import cv2 import ffmpeg  def save video cap saving file name fps 33 0        while cap isOpened            ret  frame   cap read           if ret              i width i height   frame shape 1  frame shape 0              break      process         ffmpeg          input  pipe   format  rawvideo   pix fmt  rgb24  s    x    format i width i height            output saved video file name pix fmt  yuv420p  vcodec  libx264  r fps crf 37           overwrite output            run async pipe stdin True             return process  if   name       main          cap   cv2 VideoCapture 0 cv2 CAP DSHOW      cap set 3 1920      cap set 4 1080      saved video file name    output avi      process   save video cap saved video file name       while cap isOpened             ret  frame   cap read           if ret  True              frame   cv2 flip frame 0              process stdin write                  cv2 cvtColor frame  cv2 COLOR BGR2RGB                       astype np uint8                       tobytes                                      cv2 imshow  frame  frame              if cv2 waitKey 1   amp  0xFF    ord  q                    process stdin close                   process wait                   cap release                   cv2 destroyAllWindows                   break         else              process stdin close               process wait               cap release               cv2 destroyAllWindows               break

User · Answer

Anyone who s looking for most convenient and robust way of writing MP4 files with OpenCV or FFmpeg  can see my state-of-the-art VidGear Video-Processing Python library s WriteGear API that works with both OpenCV backend and FFmpeg backend and even supports GPU encoders  Here s an example to encode with H264 encoder in WriteGear with FFmpeg backend    import required libraries from vidgear gears import WriteGear import cv2    define suitable  Codec CRF preset  FFmpeg parameters for writer output params     quot -vcodec quot   quot libx264 quot    quot -crf quot   0   quot -preset quot    quot fast quot      Open suitable video stream  such as webcam on first index i e  0  stream   cv2 VideoCapture 0      Define writer with defined parameters and suitable output filename for e g   Output mp4  writer   WriteGear output filename    Output mp4   logging   True    output params     loop over while True         read frames from stream      grabbed  frame    stream read          check for frame if not grabbed     if not grabbed        break         do something with the frame here        lets convert frame to gray for this example     gray   cv2 cvtColor frame  cv2 COLOR BGR2GRAY         write gray frame to writer     writer write gray         Show output window     cv2 imshow  quot Output Gray Frame quot   gray         check for  q  key if pressed     key   cv2 waitKey 1   amp  0xFF     if key    ord  quot q quot            break    close output window cv2 destroyAllWindows      safely close video stream stream release      safely close writer writer close      Source  https   github com abhiTronix vidgear Docs  https   abhitronix github io vidgear  More FFmpeg backend examples https   abhitronix github io vidgear gears writegear compression usage  OpenCV backend examples  https   abhitronix github io vidgear gears writegear non compression usage

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This worked for me  I added images sort   to keep the sequence order   import cv2 import numpy as np import os  image folder    data-set-race-01  video file    race-01 mp4  image size    160  120  fps   24  images    img for img in os listdir image folder  if img endswith   jpg    images sort    out   cv2 VideoWriter video file  cv2 VideoWriter fourcc   MP4V    fps  image size   img array      for filename in images      img   cv2 imread os path join image folder  filename       img array append img      out write img   out release

User · Answer

For someone whoe still struggle with the problem  According this article I used this sample and it works for me     import numpy as np import cv2  cap   cv2 VideoCapture 0     Define the codec and create VideoWriter object fourcc   cv2 VideoWriter fourcc   X264   out   cv2 VideoWriter  output mp4  fourcc  20 0   640 480    while cap isOpened         ret  frame   cap read       if ret  True          frame   cv2 flip frame 0             write the flipped frame         out write frame           cv2 imshow  frame  frame          if cv2 waitKey 1   amp  0xFF    ord  q                break     else          break    Release everything if job is finished cap release   out release   cv2 destroyAllWindows     So I had to use cv2 VideoWriter fourcc   X264   codec  Tested with OpenCV 3 4 3 compiled from sources

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