Need a easy filter sample. e.g. Create a thumbnail image every X seconds of the video

[swordry]

In FFmpeg wiki: https://trac.ffmpeg.org/wiki/Create%20a%20thumbnail%20image%20every%20X%20seconds%20of%20the%20video
we use cmd:
fmpeg -i input.flv -ss 00:00:14.435 -vframes 1 out.png
We get one picture in Specified time
ffmpeg -i input.flv -vf fps=1 out%d.png
then get lots of images. One picture per second.

How to use PyAV to achived the same goal ? Does anybody make a demo? Thanks.

BTW: by use cmd:
ffmpeg -i input.flv-r 1 -y -f image2 -s 240*320 pc%3d.jpg
use '-r' arg seems to be the same purpose， Which method is more efficient ?

[jb-alvarado]

I think you can do it more simple:

import av

count = 0
container = av.open('test_clips/test.mp4', 'r')

for packet in container.demux():
    if packet.stream.type == 'video':
        for frame in packet.decode():
            if count % 25 == 0:
                frame.to_image().save('%04d.png' % count)
            count += 1

[nishant-ever]

@jb-alvarado unless I'm misreading the code, it seems to select every frame divisible by 25 yielding frames 0, 25, 50, .... But it doesn't give a frame rate of 1 fps. Do you know if we can achieve this using the fps filter especially when the input video can have any frame rate? Thanks!

[jb-alvarado]

When you want to have images as output you can use two methods:

1. before you use the modulo operator you read the fps from input file and use this as a modulo.
2. you use the fps filter, this one drops all other frames

When you want a video output the second method is better, but you have to look here in the issues and examples for a proper way to use filters in PyAV. My knowledge about PyAV is not so deep.

Here I have try one time to change the fps, but as I remember there was some issues, and of course the queue and pipe to ffplay is not necessary.

[nishant-ever]

Thanks @jb-alvarado for a quick response. Unfortunately there are no examples for using filters. I've also asked a question in the Gitter channel for the project. Your solution here does give me some ideas but my problem is a little more complicated since I'm doing filtering on a video stream as opposed to a file on the disk. I'll see if I can come up with something. Thanks again!