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• "Undefined reference to `avcodec_alloc_frame" Error when compile and install Opencv on linux

  7 avril 2016, par Kathy Lee

  I am compiling and installing OpenCV using the steps in http://docs.opencv.org/2.4/doc/tutorials/introduction/linux_install/linux_install.html

  But during "making" it, it has error when it reaches 45%. The error message is

  ...
  
  [ 43%] Built target pch_Generate_opencv_video
  
  [ 44%] Built target opencv_video
  
  [ 44%] Built target opencv_perf_video_pch_dephelp
  
  [ 45%] Built target pch_Generate_opencv_perf_video  
  
  Linking CXX executable ../../bin/opencv_perf_video
  
  ../../lib/libopencv_videoio.so.3.1.0: undefined reference to `avcodec_alloc_frame'
  
  ../../lib/libopencv_videoio.so.3.1.0: undefined reference to `avcodec_encode_video'
  
  collect2: error: ld returned 1 exit status
  
  make[2]: *** [bin/opencv_perf_video] Error 1
  
  make[1]: *** [modules/video/CMakeFiles/opencv_perf_video.dir/all] Error 2
  
  make: *** [all] Error 2

  I downloaded and installed the latest version of ffmpeg from https://www.ffmpeg.org/.

  Anyone knows how can I fix the errors ?

  Thank you.

• FFmpeg takes too much time for generating m3u8 files from a mp4 file (166MB)

  3 août 2021, par Angele

  I am using ffmpeg in nodejs to generate 4 different resolutions (360p, 480p, 720p, 1080p).
I use a AWS lambda for each resolution and the last two take too much time.
I convert a mp4 file which has a size of 166MB into .ts files (with all segments associated)
It takes more than 900 seconds, and that's above the limit for a lambda timeout.

  


  Also my goal is to encode mp4 videos of a maximum size of 4go... and it would be to encode within 900 seconds maximum for each resolution.

  


  I used this website to find some parameters : https://docs.peer5.com/guides/production-ready-hls-vod/

  


  These are my parameters given to ffmpeg :

  


  "ffmpegParams": [
    "-vf",
    "scale=-2:1920",
    "-c:a",
    "aac",
    "-ar",
    "48000",
    "-c:v",
    "h264",
    "-profile:v",
    "main",
    "-crf",
    "20",
    "-sc_threshold",
    "0",
    "-g",
    "48",
    "-keyint_min",
    "48",
    "-hls_time",
    "4",
    "-hls_playlist_type",
    "vod",
    "-b:v",
    "5000k",
    "-maxrate",
    "5350k",
    "-bufsize",
    "7500k",
    "-b:a",
    "192k",
    "-hls_segment_filename",
    "/tmp/1080p_%03d.ts",
    "/tmp/1080p.m3u8"
]


  


  Also I tried with these parameters '-vcodec', 'libx264', '-preset', 'ultrafast' and it made it faster but it is not enough...

  


  Maybe there's something wrong with my command. If someone could maybe enlighten me ? :)

  


  Edit : I ended up using an EC Fargate, perfect for this kind of need.

  


• How do I get duration of an In Memory Video in Python / Django ?

  21 novembre 2019, par Lucas Tonon

  So I was successfully using the following code to get the duration of a saved video in Django.

  def get_video_length(file_path):
  
  command = [
  
      'ffprobe',
  
      '-v',
  
      'error',
  
      '-show_entries',
  
      'format=duration',
  
      '-of',
  
      'default=noprint_wrappers=1:nokey=1',
  
      file_path
  
    ]
  
  
  
  try:
  
      output = check_output( command, stderr=STDOUT ).decode()
  
  except CalledProcessError as e:
  
      output = e.output.decode()
  
  
  
  return output

  But now I need to get the duration of an uploaded file before saving it.
  I have a serializer with a FileField and on validate method I should check the video duration.
  For instance :

  class VideoSerializer(serializers.Serializer):
  
  video = serializers.FileField(required=True, validators=[validate_media_extension, validate_video_duration])

  Then on validate_video_duration I needed to call some method like get_video_length, but I need an alternative to get the duration from the video in memory. The object that I have is an instance of InMemoryUploadedFile (https://docs.djangoproject.com/en/2.2/_modules/django/core/files/uploadedfile/)