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• ffmpeg how to select the audio channel with the biggest bps ?

  31 octobre 2018, par Kris Roofe

  I have mp4 file with below format,

  $ ffprobe -i 70_1.mp4 -hide_banner
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '70_1.mp4':
 Metadata:
   major_brand     : qt
   minor_version   : 0
   compatible_brands: qt
   creation_time   : 2018-10-30T08:57:38.000000Z
 Duration: 00:13:55.76, start: 0.000000, bitrate: 2246 kb/s
   Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc, smpte170m/bt709/unknown, progressive), 1440x1920, 2118 kb/s, 58.75 fps, 60 tbr, 600 tbn, 1200 tbc (default)
   Metadata:
     creation_time   : 2018-10-30T08:57:38.000000Z
     handler_name    : Core Media Video
     encoder         : 'avc1'
   Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 2 kb/s (default)
   Metadata:
     creation_time   : 2018-10-30T08:57:38.000000Z
     handler_name    : Core Media Audio
   Stream #0:2(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 119 kb/s (default)
   Metadata:
     creation_time   : 2018-10-30T08:57:38.000000Z
     handler_name    : Core Media Audio

  As the auto channel is special, there is no sound when play in the browser.

  So I use ffmpeg to transfer it with ffmpeg -i 70_1.mp4 -crf 30 -b:a 23k -b:v 96k -threads 4 -map 0:0 -map 0:2 -y ooo.mp4, the generated mp4 file can play in the browser.

  $ ffprobe.exe ooo.mp4 -hide_banner
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'ooo.mp4':
 Metadata:
   major_brand     : isom
   minor_version   : 512
   compatible_brands: isomiso2avc1mp41
   encoder         : Lavf58.17.101
 Duration: 00:13:55.79, start: 0.000000, bitrate: 246 kb/s
   Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuvj420p(pc), 1440x1920, 209 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc (default)
   Metadata:
     handler_name    : Core Media Video
   Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 23 kb/s (default)
   Metadata:
     handler_name    : Core Media Audio

  But there is one issue, I need to process mp4 file with many formats, some with 1 audio channel, some with 2, So I want to know how to select the audio channel with the biggest bps.

• Losing frames when clipping videos with ffmpeg

  9 décembre 2018, par Mark C

  I seem to be losing frames when I clip videos up with ffmpeg.

  Here are the steps I take :

  [Get the Frame number to cut on] -> [turn the frame number into hh:mm:ss.ms format] -> [Run ffmpeg process]

  Here is the code :

  import subprocess
  
  
  
  def frames_to_timecode(frame,frameRate):
  
      '''
  
      Convert frame into a timecode HH:MM:SS.MS
  
      frame = The frame to convert into a time code
  
      frameRate = the frame rate of the video
  
      '''
  
      #convert frames into seconds
  
      seconds = frame / frameRate
  
  
  
      #generate the time code
  
      timeCode = '{h:02d}:{m:02d}:{s:02f}'.format(
  
      h=int(seconds/3600),
  
      m=int(seconds/60%60),
  
      s=seconds%60)
  
  
  
      return timeCode
  
  
  
  frameRate = 24.0
  
  
  
  inputVideo = r"C:\Users\aquamen\Videos\vlc-record-2018-10-23-17h11m11s-SEQ-0200_animatic_v4_20180827_short.mp4"
  
  outputVideo = r"C:\Users\aquamen\Videos\ffmpeg_test_clip001.mp4"
  
  ffmpeg = r"C:\ffmpeg\ffmpeg-20181028-e95987f-win64-static\bin\ffmpeg.exe" 
  
  
  
  endFrame = frames_to_timecode(29,frameRate)
  
  startFrame = frames_to_timecode(10,frameRate)
  
  
  
  subprocess.call([ffmpeg,'-i',inputVideo,'-ss',startFrame,'-to',endFrame,outputVideo])

  Here is a image of the original video and the clipped video with the time codes showing a frame was lost in process. The time code should show 00:01:18:10 instead its 00:01:18:11.

  

  

• Cannot use pydub.AudioSegment on audio files downloaded by youtube-dl library

  26 octobre 2018, par Han M

  After I download a audio clip from a youtube link by the youtube-dl library, I cannot use pydub.AudioSegment to slice the audio file. The following is the information about my code.

  import youtube_dl
  
  options = {
  
          'format': 'bestaudio/best',
  
          'extractaudio': True,  # only keep the audio
  
          'audio-format': "wav",  # convert to wav
  
          'outtmpl': whole_path,  # name the file the ID of the video
  
          'noplaylist': True,  # only download single song, not playlist
  
          'audioquality': 1
  
  }
  
  with youtube_dl.YoutubeDL(options) as ydl:
  
      print('url is:', web_url)
  
      ydl.download([web_url])
  
  
  
  from pydub import AudioSegment
  
  audio_data = AudioSegment.from_wav(path_to_downloaded_file)

  Then, I got an error as follows first on Mac and second on Linux :

  b'avconv version 12.3, Copyright (c) 2000-2018 the Libav developers\n  built on Jul 26 2018 18:08:50 with Apple LLVM version 9.1.0 (clang-902.0.39.2)\n/Users/***/random17560390.wav: Invalid data found when processing input\n'
  
  
  
  b'ffmpeg version 2.8.15-0ubuntu0.16.04.1 Copyright (c) 2000-2018 the FFmpeg developers\n  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609\n  configuration: --prefix=/usr --e
  
  xtra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-
  
  shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-li
  
  bbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmod
  
  plug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-li
  
  bspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --e
  
  nable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv\n  libavutil      54. 31.100 / 54.
  
   31.100\n  libavcodec     56. 60.100 / 56. 60.100\n  libavformat    56. 40.101 / 56. 40.101\n  libavdevice    56.  4.100 / 56.  4.100\n  libavfilter     5. 40.101 /  5. 40.101\n  libavresa
  
  mple   2.  1.  0 /  2.  1.  0\n  libswscale      3.  1.101 /  3.  1.101\n  libswresample   1.  2.101 /  1.  2.101\n  libpostproc    53.  3.100 / 53.  3.100\n[wav @ 0x20854c0] invalid start
  
   code [0][0][0][28] in RIFF header\n/home/users/test_download/random10485395.wav: Invalid data found when processing input\n'

  I think the problem might be about the encoding on the downloaded files by youtube-dl. I can use pydub.AudioSegment on other normal .wav files. After checking the details of the downloaded file by youtube-dl, I found the following feature :

  Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, stereo, fltp, 125 kb/s (default)

  It is different from other normal .wav files, which have the following :

  Stream #0:0: Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, 2 channels, s16, 1411 kb/s