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• How to save frame from VOB with correct size ?

  18 mars 2017, par Paulo Barretto

  I am saving single frames from a vob file with ffmpeg.

  ffprobe shows for my vob file :

  Stream #0:1[0x1e0] : Video : mpeg2video (Main), yuv420p(tv), 720x480
  [SAR 8:9 DAR 4:3], Closed Captions, 3750 kb/s, 29.97 fps, 29.97 tbr,
  90k tbn, 59.94 tbc

  My command line is

  ffmpeg -i File1.vob -ss 10 -q:v 2 -vframes 1 -an -sn frame10s.jpg

  My jpeg files are being saved with 720x480, horizontally stretched. How can I make them be saved with correct display ratio 640x480 ?

• Read, process and save video and audio with FFMPEG

  3 mai 2017, par sysseon

  I want to open a video resource with ffmpeg on Python, get the read frames from the pipe, modify them (e.g. put the timestamp with OpenCV) and write the result to an output video file. I also want to save the audio source with no changes.

  My code (with no audio and two processes) :

  import subprocess as sp
  
  import numpy as np
  
  # import time
  
  # import cv2
  
  
  
  FFMPEG_BIN = "C:/ffmpeg/bin/ffmpeg.exe"
  
  INPUT_VID = 'input.avi'
  
  res = [320, 240]
  
  
  
  command_in = [FFMPEG_BIN,
  
                '-y',  # (optional) overwrite output file if it exists
  
                '-i', INPUT_VID,
  
                '-f', 'image2pipe',  # image2pipe or rawvideo?
  
                '-pix_fmt', 'bgr24',
  
                '-vcodec', 'rawvideo',
  
                '-']
  
  
  
  command_out = [FFMPEG_BIN,
  
                 '-y',  # (optional) overwrite output file if it exists
  
                 '-f', 'rawvideo',
  
                 '-vcodec', 'rawvideo',
  
                 '-s', '320x240',
  
                 '-pix_fmt', 'bgr24',
  
                 '-r', '25',
  
                 '-i', '-',
  
                 # '-i', INPUT_VID,    # Audio
  
                 '-vcodec', 'mpeg4',
  
                 'output.mp4']
  
  
  
  pipe_in = sp.Popen(command_in, stdout=sp.PIPE, stderr=sp.PIPE)
  
  pipe_out = sp.Popen(command_out, stdin=sp.PIPE, stderr=sp.PIPE)
  
  
  
  while True:
  
      # Read 320*240*3 bytes (= 1 frame)
  
      raw_image = pipe_in.stdout.read(res[0] * res[1] * 3)
  
      # Transform the byte read into a numpy array
  
      image = np.fromstring(raw_image, dtype=np.uint8)
  
      image = image.reshape((res[1], res[0], 3))
  
      # Draw some text in the image
  
      # draw_text(image)
  
  
  
      # Show the image with OpenCV (not working, gray image, why?)
  
      # cv2.imshow("VIDEO", image)
  
  
  
      # Write image to output process
  
      pipe_out.stdin.write(image.tostring())
  
  
  
  print 'done'
  
  pipe_in.kill()
  
  pipe_out.kill()

  1. Could it be done with just a process ? (Read the input from a file,
     put it in the input pipe, get the image, process it, and put it in
     the output pipe to be saved into a video file)
  2. How can I save the audio ? In this example, I could use ’-i
     INPUT_VID’ in the second process to get the audio channel, but my
     source will be a RTSP, and I don’t want to create a connection for
     each process. Could I put video+audio in the pipe and rescue and
     separate it with numpy ? How ?
  3. I use a loop to process the frames and wait until I get an error.
     How can I check if all frames are already read ?
  4. Not important, but if I try to show the images with OpenCV
     (cv2.imshow(...)), I only see a gray screen. Why ?

• Save the stream to mp4 files

  5 mai 2012, par Ruslan Sharipov

  How can I keep the flow (protocol rtsp, codec h264) in file (container mp4) ? That is, on input an endless stream (with CCTV camera), and the output files in mp4 format size of 5-10 minutes of recording time.

  OS : debian, ubuntu
  Software : vlc, ffmpeg (avconv)

  Currently this scheme is used :

  cvlc rtsp://admin:admin@10.1.1.1:554/ch1-s1 --sout=file/ts:stream.ts
  
  ffmpeg -i stream.ts -vcodec copy -f mp4 stream.mp4

  But it can not record video continuously (between restarts vlc is a loss of about 10 seconds of live video)