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• How to create a video out of frames without saving it to disk using python ?

  6 septembre 2022, par brenodacosta

  I have a function that returns a frame as result. I wanted to know how to make a video out of a for-loop with this function without saving every frame and then creating the video.

  


  What I have from now is something similar to :

  


  import cv2
out = cv2.VideoWriter('video.mp4',cv2.VideoWriter_fourcc(*'DIVX'), 14.25,(500,258))
for frame in frames:
    img_result = MyImageTreatmentFunction(frame) # returns a numpy array image
    out.write(img_result)
out.release()


  


  Then the video will be created as video.mp4 and I can access it on memory. I'm asking myself if there's a way to have this video in a variable that I can easily convert to bytes later. My purpose for that is to send the video via HTTP post.

  


  I've looked on ffmpeg-python and opencv but I didn't find anything that applies to my case.

  


• Web Based Playback of iOS Videos with Orientation Flag

  3 mars 2012, par shanee

  We just recently created an iPhone app for one of our system that allows users to upload picture and video content to our services. The last major hitch we are running into is how to handle videos that are uploaded in an orientation other than Horizontal Right. Apparently if your playback system does not account for the orientation flag sent with the video then it will play upside down or sideways.

  The correct approach appears to be that the playback system should take the orientation flag into account just prior to playback. This is the way Apple handles it directly on the device as well as through Quicktime.

  SO my first hope is that someone is aware of a web based (HTML5 or Flash) player that is capable of rotating a video during playback based on either the video orientation metadata or based on a passed flag (we already have the necessary flag available in the DB if we need to just pass it manually). If you know of any such player then PLEASE SHARE !

  If you aren't aware of such a player, then has anyone had any luck rotating their videos using FFMPEG or MEncoder ? We did a few hours of testing last week and weren't able to get any decent results from the two heavy hitters mentioned there.

  Failing ALL OF THAT, is it possible to have the iPhone upload a video or image in a specified direction ?

  Any of the three will work for me, but I would prefer to do whatever is standard (if one exists).

  Any help is much appreciated !

• Relocated ffmpeg example files fail

  17 novembre 2020, par CT99

  I'm trying to use some ffmpeg calls in my own program, the basis of which I'm editing the ffmpeg example program remuxing.c. I'm trying to use some of the ffmpeg calls in my own program.

  


  I'm running Ubuntu 18.04.5 on a generic Linux box.

  


  To help better understand what I've done and where I've having problems, I'll out line what I've done and what is not working.

  


  Steps I've successfully completed :

  


  — I've have downloaded the ffmpeg code base and example files

  


  — Next I did a './configure', then 'make', then 'make install' and 'make examples' to make the libraries and examples

  


  — I tested some of the examples and they ran fine from the default install directory

  


  — specifically, when I test remuxing.c in the original ffmpeg downloaded dir — compile and run — it works fine

  


      ./remuxing /data/iphone-h264.m4v /tmp/test15.ts


  


  — this creates a .ts output file that I can test and is readable by vlc

  


  Having ensured that I correctly compiled and tested ffmpeg source and its example files, I next move to working my own program based on the example remuxing.c

  


  — I copied the original remuxing.c into my own test directory structure

  


  — I make it by running this to link in the required ffmpeg libraries (I think)

  


      cc -DLINUX -o remuxing remuxing.c -I ../ffmpeg/libavformat -lavformat -I ../ffmpeg/libavcodec -lavcodec -I ../ffmpeg/libswresample -lswresample -I ../ffmpeg/libavutil -lavutil -lpthread -lm


  


  — however when I try to generate a test16.ts file (to know it is different from the one I created before) I get an error :

  


      ./remuxing /data/iphone-h264.m4v /tmp/test16.ts
    Could not open input file '/data/iphone-h264.m4v’ Error occurred: Invalid data found when processing input


  


  This is the exact same video file the same program converted from the installed doc/examples directory.

  


  QUESTION — why is this happening — what am I doing wrong ?

  


  I guess I may not be properly linking in the ffmpeg libraries ?? — but I'm not sure what I'm doing wrong.

  


  I can also post my makefiles if that would help.

  


  Would be most appreciative for any help — thank you in advance.