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  • Writing frames from camera using skvideo.io.FFmpegWriter

    28 juin 2018, par Liam Deacon

    I’m trying to finely control the video encoding of camera image frames captured on the fly using skvideo.io.FFmpegWriter and cv2.VideoCapture, e.g.

    from skvideo import io
    
import cv2
    

    
fps = 60
    
stream = cv2.VideoCapture(0)                    # 0 is for /dev/video0
    
print("fps: {}".format(stream.set(cv2.CAP_PROP_FPS, fps)))
    

    
stream.set(cv2.CAP_PROP_FRAME_WIDTH, 1920)
    
stream.set(cv2.CAP_PROP_FRAME_HEIGHT, 1080)
    
print("bit_depth: {}".format(stream.set(cv2.CAP_PROP_FORMAT, cv2.CV_8U)))
    

    
video = io.FFmpegWriter('/tmp/test_ffmpeg.avi', 
    
            inputdict={'-r': fps, '-width': 1920, '-height': 1080},
    
            outputdict={'-r': fps, '-vcodec': 'libx264', '-pix_fmt': 'h264'}
    
)
    

    
try:
    
    for i in range(fps*10):  # 10s of video
    
        ret, frame = stream.read()
    
        video.writeFrame(frame)
    
finally:
    
    stream.release()
    

    
try:
    
    video.close()
    
except:
    
    pass

    However, I get the following exception (in Jupyter notebook) :

    ---------------------------------------------------------------------------
    
TypeError                                 Traceback (most recent call last)
    

    
 in <module>()
    
     18     while range(fps*10):
    
     19         ret, frame = stream.read()
    
---> 20         video.writeFrame(frame)
    
     21 except BaseException as err:
    
     22     raise err
    

    
/usr/local/lib/python3.6/site-packages/skvideo/io/ffmpeg.py in writeFrame(self, im)
    
    446         T, M, N, C = vid.shape
    
    447         if not self.warmStarted:
    
--> 448             self._warmStart(M, N, C)
    
    449 
    
    450         # Ensure that ndarray image is in uint8
    

    
/usr/local/lib/python3.6/site-packages/skvideo/io/ffmpeg.py in _warmStart(self, M, N, C)
    
    412         cmd = [_FFMPEG_PATH + "/" + _FFMPEG_APPLICATION, "-y"] + iargs + ["-i", "-"] + oargs + [self._filename]
    
    413 
    
--> 414         self._cmd = " ".join(cmd)
    
    415 
    
    416         # Launch process
    

    
TypeError: sequence item 3: expected str instance, int found
    
</module>

    Changing this to video.writeFrame(frame.tostring()) results in ValueError: Improper data input, leaving me stumped.

    How should I go about writing each frame (as returned by OpenCV) to my FFmpegWriter instance ?

    EDIT

    The code works fine if I remove inputdict and outputdict from the io.FFmpegWriter call, however this defeats the purpose for me as I need fine control over the video encoding (I am experimenting with lossless/near-lossless compression of the raw video captured from the camera and trying to establish the best compromise in terms of compression vs fidelity for my needs).

  • How to display live web camera video into video player using ffmpeg

    30 octobre 2013, par Akash Langhani

    I want to use live camera video and play same time in a video player, means record and play parallel, can ffmpeg perform this, if yes then how.

  • Revision 6724 : On ajoute la CSS privée plus quelques éléments de CSS pour la gestion des ...

    27 juin 2012, par kent1 — Log

    On ajoute la CSS privée plus quelques éléments de CSS pour la gestion des plugins
    On utilise #PRODUIRE sur cette CSS pour la générer en statique
    Amélioration du formulaire de gestion des langues
    On ajoute un lien vers la page de gestion des plugins dans la notice des plugins

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