Recherche avancée

Sur d’autres sites (14594)

• Lossless trim and crop of MJPEG video

  28 avril 2021, par prouast

  I am working on a project where I need to trim and crop MJPEG videos without any re-encoding. I have working code that accomplishes this by exporting the relevant frames as JPEGs, cropping them individually, and then joining them back together into an MJPEG.

  


  However, this seems quite inefficient and slow. I am looking for pointers how to improve this approach. For example, would it be possible to store the JPEGs in-memory ?

  


  import ffmpeg
import os
import shutil
import subprocess

def lossless_trim_and_crop(path, output_path, start, end, x, y, width, height, fps):
  # Trim the video in time and export all individual jpeg with ffmpeg + mjpeg2jpeg
  jpeg_folder = os.path.splitext(output_path)[0]
  jpeg_path = os.path.join(jpeg_folder, "frame_%03d.jpg")
  stream = ffmpeg.input(path, ss=start/fps, t=(end-start)/fps)
  stream = ffmpeg.output(stream, jpeg_path, vcodec='copy', **{'bsf:v': 'mjpeg2jpeg'})
  stream.run(quiet=True)
  # Crop all individual jpeg with jpegtran
  for filename in os.listdir(jpeg_folder):
    filepath = os.path.join(jpeg_folder, filename)
    out_filepath = os.path.splitext(filepath)[0] + "_c.jpg"
    subprocess.call(
      "jpegtran -perfect -crop {}x{}+{}+{} -outfile {} {}".format(
        width, height, x, y, out_filepath, filepath), shell=True)
    os.remove(filepath)
  # Join individual jpg back together
  cropped_jpeg_path = os.path.join(jpeg_folder, "frame_%03d_c.jpg")
  stream = ffmpeg.input(cropped_jpeg_path, framerate=fps)
  stream = ffmpeg.output(stream, output_path, vcodec='copy')
  stream.run(quiet=True)
  # Delete jpeg directory
  shutil.rmtree(jpeg_folder)


  


• AE per frame rendering FFMPEG forming to video

  9 février 2018, par Deckard Cain

  I’m trying to setup an automated per frame rendering system using After Effects and FFMPEG. The idea here is that my slave nodes (running AE), will generate the frames and save them immediately to a Samba share (this way I can team multiple slaves together to tackle the same project file and we aren’t writing an 8GB AVI file, then compressing and deleting it when we could just render 300MB of frames and form it).

  The database and Samba share are running on FreeBSD. This machine will then take those frames and use FFMPEG to combine them into an MP4 video.

  The issue that I’m running into, is that when I render out the After Effects project file directly to an AVI file (one slave, no individual frame rendering), the video length is 1:31. When I render out the exact same project file into individual frames, then run it through FFMPEG to combine and compress them, the output is 1:49.

  I have tried a billion different things to make the length of the video the same, but can’t seem to make it so :/

  aerender.exe -mp -project %PROJECTFILE% -comp %COMPOSITION% -output [########].jpg

  ^Keep in mind, there may be 99999999 frames, or as little as 1 that needs to be rendered (if we need to re-render a specific section because of an asset change)

  ffmpeg -nostdin -i %FRAMELOCATION% -c:v libx264 -preset veryfast -an -y outputVideo.mp4

• How to stack several videos using ffmpeg ?

  13 juillet 2019, par John

  I have four cameras that are recording videos and wand to stack all videos into one video file. The final video must be a 2x2 grid.

  

  THE HARD PART is that sometimes cameras are not recording simultaneously.

  Here you can see one situation of how cameras are recording :

  Camera 1 timeline: |recording....................................|
  
  Camera 2 timeline: |stopped....|recording........................|
  
  Camera 3 timeline: |recording.........|stopped....|recording.....|
  
  Camera 4 timeline: |recording..................|stopped..........|

  Explanation :

  • Camera 1 is recording all time.
  • Camera 2 is starting recording later.
  • Camera 3 is recording, then stopped a period of time, then again recording.
  • Camera 4 is recording a period of time, then stopped.

  In the final video I want to synchronize each video by timestamps.

  If a camera is stopped a period of time then at its position must be a black portion.

  How can I do this ?