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  • Created a black frame movie using ffmpeg

    28 juillet 2015, par Yunxiao Jia

    ffmpeg -i "data%04d_Projection_z_temperature_density.png" -r 47 -b 14M Projection_test_movie.mp4

    This is the command i have used, the output seems fine, but when I open it with realplayer, it just plain back. Need Help, thank you !

  • Use FFMPEG to Merge many frames into one video ?

    14 novembre 2015, par SpoiledTechie.com

    With a project I am working on, I am taking one video, extracting frames from within the middle, from 00:55:00 to 00:57:25. After I extract these images, I am modifying them via code and I then need to compile these images back into a video. To finish it off, I will then merge the video back into the original video.

    Ive already pulled the frames from the video, modified them, but now I need to merge them back together into a video.

    I used this question to check the format, but I am not getting the correct output.

    http://superuser.com/questions/563570/use-ffmpeg-for-video-to-frames-then-frames-to-video-with-original-sound

    Here is my current input to FFMPEG :

    -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj0.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj1.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj2.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj3.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj4.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj5.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj6.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj7.Bmp" -r 24.97 -i "C:\Users\scott\AppData\Local\Temp\iOs91azj8.Bmp" -an -r 24.97 "C:\Users\scott\AppData\Local\Temp\ewELJdA8.mp4"

    EDIT

    My current output gives me a video that doesn’t play. So for some reason, the merging of frames isn’t the correct format and FFMPEG isn’t giving me a reasonal output to work with.

    How do I merge frames together into a video ?

  • video processing on android using ndk with ffmpeg and opencv is very slow

    22 septembre 2017, par Zhiqiang Li

    I’m doing some video processing on android using ndk.

    What I’m doing now is decode the video using ffmpeg, grab the frame, convert it to opencv mat, then overlay some images on it, then convert it back to avframe, encode it back to a video.

    But it’s very slow ! It takes about 50 seconds to process a 480*480 video with 15 fps.

    I tried to do this using opengl es, reading the result image using glReadPixels, but from what I understand, glReadPixels doesn’t really work on some devices. So I had to give it up.

    As I understand, I have some very expensive operations in my current workflow,

    1. covert a AVFrame from yuv to bgr color space, then convert to opencv mat
    2. overlay a mat on another mat
    3. covert a opencv mat to AVFrame, then convert the frame from bgr to yuv space, then encode it into a video.

    So, are there ways to improve my current workflow ?

    I’m adding multithread feature, but only devices with multicore cup can benefit from that.