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• Input seeking for frame at specified timestamp with Py-AV

  9 décembre 2019, par neonScarecrow

  I have a project already using Py-AV and am trying to replicate a specific ffmpeg command. The goal is to get a frame roughly around the specified timestamp.

  Here’s the ffmpeg commmand :
  https://trac.ffmpeg.org/wiki/Seeking

  ffmpeg -ss 14 -i https://some_url.mp4 -frames:v 1 frame_at_14_seconds.jpg

  Here’s my code :

      #return one frame around 14 seconds into the movie
  
      target_sec = 14 
  
      container = av.open('https://some_url.mp4', 'r')
  
      container.streams.video[0].thread_type = 'AUTO'
  
      video_stream = next(s for s in container.streams if s.type == 'video')
  
      time_base = float(video_stream.time_base)
  
      target_timestamp = int(target_sec / time_base) + video_stream.start_time
  
      video_stream.seek(target_timestamp)
  
      for frame in container.decode(video_stream):
  
          frame.to_image().save('frame_at_14_seconds.jpg')
  
          break

  Additionally, I have found any documentation about this, but does anyone know if either command (ffmpeg/av.open) is downloading the entire file to a tmp file behind the scenes. I’m looking for a less memory-intensive way to read a frame for every second in an up to 60 second video.

• Video Analysis using .dav file in python

  2 mars 2023, par FRECEENA FRANCIS

  I have tried the following code :

  


  #!/usr/bin/python

print ("Converting all of the .dav files in this current directory into .mp4 files using ffmpeg")
import os
from subprocess import call
import ffmpeg as ffmpeg

files = [f for f in os.listdir('.') if os.path.isfile(f)]
for f in files:
    ext = f.split(".")[-1]
    if ext == "dav" or ext == "DAV":
        mp4Name = f.replace("dav", "mp4")
        print("Converting: " + f)
        ffmpeg ,'-y', '-i', f, "-vcodec", "libx264", "-crf", "24", mp4Name

        print("Converted: " + f)


  


  Got the output as below without no error :

  


  Converting all of the .dav files in this current directory into .mp4 files using ffmpeg
Converting: file.dav
Converted: file.dav


  


  But am stuck here as am new to this. what to do next for further analysis for example fire in video.

  


• How to repair a raw H.264 stream using FFmpeg

  13 janvier 2020, par Chris Kennedy

  I apologize if I start rambling or seem incoherent.

  Preface : My house caught on fire last week.

  I have been trying to get the footage off my security camera system (Zmodo, don’t ever buy this crap) to share with the fire marshal and my insurance. I can’t get it off the "proper" way because the box doesn’t detect any drive or any file system I throw at it, and none of their viewing apps (for Android or Windows) allow video downloads.

  I was able to get the files directly from the system’s hard drive, but they’re (of course) messed up in such a way that I can’t just open up VLC (or even Zmodo’s own viewing software !) and view them. I have spent several hours scouring the web for various ways to run it through FFmpeg to see if it can repair the file, but I’ve had no luck so far and my mind is already stretched thin with everything else.

  This is the output from ffprobe :

  ffprobe version 4.2.1 Copyright (c) 2007-2019 the FFmpeg developers
  
    built with gcc 9.1.1 (GCC) 20190807
  
    configuration: --enable-gpl --enable-version3 --enable-sdl2 --enable-fontconfig --enable-gnutls --enable-iconv --enable-libass --enable-libdav1d --enable-libbluray --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-libopus --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libtheora --enable-libtwolame --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libzimg --enable-lzma --enable-zlib --enable-gmp --enable-libvidstab --enable-libvorbis --enable-libvo-amrwbenc --enable-libmysofa --enable-libspeex --enable-libxvid --enable-libaom --enable-libmfx --enable-amf --enable-ffnvcodec --enable-cuvid --enable-d3d11va --enable-nvenc --enable-nvdec --enable-dxva2 --enable-avisynth --enable-libopenmpt
  
    libavutil      56. 31.100 / 56. 31.100
  
    libavcodec     58. 54.100 / 58. 54.100
  
    libavformat    58. 29.100 / 58. 29.100
  
    libavdevice    58.  8.100 / 58.  8.100
  
    libavfilter     7. 57.100 /  7. 57.100
  
    libswscale      5.  5.100 /  5.  5.100
  
    libswresample   3.  5.100 /  3.  5.100
  
    libpostproc    55.  5.100 / 55.  5.100
  
  [h264 @ 000002479ee1c180] Format h264 detected only with low score of 1, misdetection possible!

  Then this repeats several dozen times :

      Last message repeated 1 times
  
  [h264 @ 000002479ee1de40] decode_slice_header error
  
  [h264 @ 000002479ee1de40] no frame!
  
  [h264 @ 000002479ee1de40] non-existing PPS 0 referenced

  And it finishes off with this :

  [h264 @ 000002479ee1c180] Could not find codec parameters for stream 0 (Video: h264, none): unspecified size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, h264, from '.\recfile_-200102-130000-135959-00001100.264':
  
    Duration: N/A, bitrate: N/A
  
      Stream #0:0: Video: h264, none, 25 fps, 25 tbr, 1200k tbn, 50 tbc

  I have tried several options with ffmpeg, including force_key_frames, setting the analyzeduration and probesize options to max_int, tried a -c copy, forcibly specified x264, tried to force a specific resolution (which it should all be standard HD video), and several others that I can’t recall at the moment.

  The video files are also accompanied by a .IDX file, but I haven’t figured out how important they are if they are at all to the video file.

  I can provide links to the smallest video and its associated IDX if needed, but if anyone can think of anything else to try on these files I’d greatly appreciate it.