FFMpegWriter input and output dict format about scikit-video HOT 11 CLOSED

Until today we don't have a simple documentation for outputdict from FFmpegWriter. Is one of the most important things on this lib. How can I define how to write an video? Nowhere with explanations? A single example?

from scikit-video.

Ah good catch. I will have to update the documentation about FFmpegWriter. I'm in the process of writing more example-based documentation. You can see the current progress (with dict examples for I/O) here:

http://www.scikit-video.org/dev/examples.html

from scikit-video.

Hey guys. Check this code :

from skvideo.io import VideoWriter
import numpy
writer = VideoWriter(filename, frameSize=(w, h))
writer.open()
while True:
.......
writer.write("some random video frame- from iteration process")
.......
writer.release()

It does output a video file, however the quality of it is very poor beyond the first keyframe. Your skvideo documentation states that FFmpegWriter should be used for more customisation of parameters, however that does not exist.

http://www.scikit-video.org/dev/examples.html this link does not provide an example of video file written to disk frame by frame.

What's wrong with this thread? Why is there such bad quality of output? Why is there such bad quality of documentation?

Why is there no proper way to write video in Python, in 2016? :)

from scikit-video.

Ah! I did forget to add an example on the webpage regarding high-quality h264 encodes.

If you want to output a good quality video (frame by frame), you can start from the below example which uses the libx264 codec with bitrate set to 30MBps which encodes random noise:

import skvideo.io
import skvideo.measure
import numpy as np


outputfile = "test.mp4"
outputdata = np.random.random(size=(30, 480, 640, 3)) * 255
outputdata = outputdata.astype(np.uint8)

# start the FFmpeg writing subprocess with following parameters
writer = skvideo.io.FFmpegWriter(outputfile, outputdict={
    '-vcodec': 'libx264', '-b': '30000000'
})

for i in range(30):
    writer.writeFrame(outputdata[i])
writer.close()

inputdata = skvideo.io.vread(outputfile)

# test each frame's SSIM score
mSSIM = 0
for i in range(30):
    mSSIM += skvideo.measure.ssim(np.mean(inputdata[i], axis=2), np.mean(outputdata[i], axis=2))
mSSIM /= 30.0

print mSSIM

You can play with the coding parameters and see how it is reflected in the measured mean SSIM value. BTW, the flags in the outputdict are passed directly to FFmpeg through the CLI.

Perhaps there is a better, more generic way to write high quality video as h264, rather than explicitly using a dictionary of parameters. I think the current approach is flexible although currently poorly documented.

from scikit-video.

I have now added this to the dev branch of the website

from scikit-video.

It would be awesome if you could state somewhere whether it's possible to grab frames from a webcam? Have not been able to find any documentation on that in the latest release, and had no luck with ffmpegreader so far..

from scikit-video.

from scikit-video.

Hi,
Thanks for the nice package!
I am working with skvideo and trying to output a video but while the code above (high quality video) runs and produces a video file, the created video is not being able to be read by Window media player/ seems to not have any frames. Do you know what is causing the problem and how could I fix this?

from scikit-video.

Is the file size larger than 0? You can try playing it with VLC

from scikit-video.

Hi, I downloaded VLC and it works perfectly! Thank you.

from scikit-video.

Examples: http://www.scikit-video.org/stable/examples.html

If you want to go beyond this, you can check out the documentation for ffmpeg's output flags.

from scikit-video.