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• Generating videos with cv2 not working on ubuntu server

  1er mars 2023, par Cosmo

  I'm trying to generate a video from a series of jpg on an aws ubuntu instance. The video generation goes fine but when I download the video and try to play it I get this error from windows :

  


  We can't open output.mp4. This may be because the file type is unsupported, the file extension is incorrect or the file is
corrupt.
0xC00D36C4


  


  When I run the code on my windows machine I don't get the error and the video plays fine (code below) :

  


  import cv2
import os

path = 'out_frames/'
out_video_name = 'output.avi'

pre_imgs = os.listdir(path)
# print(pre_imgs)
img = []

for i in pre_imgs:
    i = path+i
    # print(i)
    img.append(i)


size = (1000,1000)
# print(size)

video = cv2.VideoWriter('output.mp4', cv2.VideoWriter_fourcc(*'mp4v'), 24, size) #output video name, fourcc, fps, size

for i in range(len(img)):
    video.write(cv2.imread(img[i]))
    print('frame ', i+1, ' of ', len(img))

video.release()
print('Video made! Return to previous page to download')



  


  I've tried :

  


  

  • Using different encoders

  


  • reinstalling opencv - sudo pip install opencv-contrib-python

  


  • reinstalling ffmpeg - sudo apt-get install ffmpeg

  


  • installing these libraries - sudo apt-get install libx264-dev sudo apt-get install libx265-dev libnuma-dev

  


  • experimented outputting .avi's instead of .mp4's

  


  


  Edit :
This doesn't solve my problem but may help understanding it. I tried converting the 'broken' mp4's to an avi using a website and windows is able to play this avi with 1 caveat being the video is choppy (almost like the frames are missorderd ?)
note - when I generate the video files using the code on windows there's no choppy effect.

  


  I'm at a loss.
Thanks in advance :)

  


• Create fragmented MP4 from MP3

  25 octobre 2020, par Stefan Falk

  I am trying to convert an MP3 file to a fragmented MP4 like this :

  


  ffmpeg -i input.mp3 -strict experimental -acodec aac -b:a 256k -f mp4 \
       -movflags faststart+frag_keyframe+empty_moov+separate_moof output.mp4 


  


  However, using Bento4 I can see that there is just one giant mdat object instead of a series of those :

  


  [ftyp] size=8+24
  major_brand = isom
  minor_version = 200
  compatible_brand = isom
  compatible_brand = iso2
  compatible_brand = iso6
  compatible_brand = mp41
[moov] size=8+701
  ...
[moof] size=8+62364
  ...
[mdat] size=8+5794679
[mfra] size=8+59
  [tfra] size=12+31, version=1
    track_ID = 1
    length_size_of_traf_num = 0
    length_size_of_trun_num = 0
    length_size_of_sample_num = 0
  [mfro] size=12+4
    mfra_size = 67


  


  I think what I want is this :

  


  

  


  (source)

  


  But I can't seem to be able to get this from ffmpeg.

  


  I found some other options here like

  


  $ ffmpeg -h muxer=ismv&#xA;...&#xA;-frag_duration     <int>   E.... Maximum fragment duration&#xA;-min_frag_duration <int>   E.... Minimum fragment duration&#xA;-frag_size         <int>   E.... Maximum fragment size&#xA;</int></int></int>

  


  but playing around with these didn't change the output.

  


  How can I create fragments of a specific sice e.g. 5 seconds each ?

  


• ffmpeg options that work with Chrome

  21 avril 2015, par James

  I am trying to find the magic options that make mp4 work in Chrome. I think my videos were working, but don’t seem to any more after Chrome updated.

  Chrome, Version 41.0.2272.101 (Windows)

  I tried some other machines and found some of the videos worked on older versions, and my Mac seems to still work on the latest Chrome.

  I am using the ffmpeg options to convert from png series,

  ffmpeg -framerate 10 -i dance%02d.png  -r 10 -pix_fmt yuv420p dance.mp4

  Some videos work, some don’t, some work some of the time, or stop half way through.

  I tried various other options like,

  ffmpeg -start_number 16 -framerate 10 -i dance%02d.png -r 10 -an -s hd720 \
  
  -vcodec libx264 -pix_fmt yuv420p -preset slow -profile:v baseline \
  
  -movflags faststart -y dance.mp4

  but this just seemed to make things worse.

  here is one of the videos,
  http://www.botlibre.com/media/a786625.mp4

  and another one,
  http://www.botlibre.com/media/a812450.mp4

  Firefox seems to work no problem, on any version, grey background though.
  IE works fine, white background.
  Safari works, grey background.

  Another thing, they videos used to have white background on older Chrome version, but now are grey, except on Mac still white.

  and one more thing. Webm format works, but anyone know the option to remove transparency ? I’m using,

  ffmpeg -i dance%02d.png  -r 10 -c:v libvpx -crf 10 -b:v 512k -c:a libvorbis dance.webm

  just want a solid white background.