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• Different results using qt-faststart and "ffmpeg -movflags +faststart"

  31 mars 2020, par Juan Ignacio Sánchez

  I have a set of videos generated by security cameras, which have the MOOV atom at the end of the file, like this :

  ftyp (32 bytes)
  
  free (8 bytes)
  
  mdat (29647845 bytes)
  
  moov (42054 bytes)

  I want to serve these files using progressive downloads (pseudo streaming) and it’s the only acceptable way to do it.

  Knowing that I tried to use tools like qt-faststart or directly ffmpeg with the corresponding flags (-movflags +faststart). Other detail is that I’m running this on a low profile machine, and FFmpeg takes like 6 8 seconds to finish (even using -c copy) and the other tool results to be much more efficient since it only moves some bytes, taking less than a second to finish. The thing here is that qt-faststart produces a video that can’t be pseudo streamed but ffmpeg does it. Here are some comparisons :

  ffmpeg :

  ftyp (32 bytes)
  
  moov (42422 bytes)
  
  free (8 bytes)
  
  mdat (29647845 bytes)

  qt-faststart :

  ftyp (32 bytes)
  
  moov (42054 bytes)
  
  free (8 bytes)
  
  mdat (29647845 bytes)

  As you can see, FFmpeg adds some extra bytes on the MOOV atom, can anyone point me in some research direction ? Thank you all.

• Ffmpeg "no directory found" when passing in a path to the mp3 file

  21 février 2020, par Eugene Levinson

  How my code should work :

  Join the voice channel with the user who sent the command

  Download the video using the link

  Save it as random 16 digit number .mp3

  Then pass the path to the FFmpeg player to play

  My code :

  The random 16 digit number

  def get_digits(amount):
  
      st = ""
  
      for i in range(amount):
  
          n = random.randint(0,9)
  
          st = st + str(n)
  
  
  
      return int(st)

  Downloading the file

  def get_path(url):
  
  
  
      #checking if the directory exists
  
      os.makedirs('Music', exist_ok=True)
  
  
  
      title = YouTube(url).streams.get_highest_resolution().title
  
      current_directory = pathlib.Path(__file__).parent.absolute()
  
  
  
      print(str(current_directory))
  
  
  
      #name for the music
  
      name = str(get_digits(16))
  
  
  
      YouTube(url).streams.filter(only_audio=True).order_by("bitrate").desc().first().download("Music",name )
  
      return str(str(current_directory) + "/Music/" + name + ".mp3")

  This gets called on command play

  #function to connect to a voice chat
  
  async def join_auth(ctx):
  
      try:
  
          channel = ctx.author.voice.channel
  
          vc = await channel.connect()
  
          return vc
  
      except Exception as e:
  
          logg("Exception occured when joining a voice channel: " + str(e),"error",str(ctx.guild.name), str(ctx.guild.id))

  The error I get :
  C:\Users\Eugene\Desktop\Discord bot/Music/4343941300524002.mp3: No such file or directory
  But the directory C:\Users\Eugene\Desktop\Discord bot\Music exists and it does contain the 4343941300524002.mp3 file. Does anyone know why do I get the error ?

• FFmpeg to convert "many" mp3 files to wav files

  21 janvier 2020, par ab123

  I wish to convert some hundred thousand small-duration(< 5 sec) mp3 files to wav files. But the process presently takes several days to complete. I would like to know if there is a faster way than what I am currently doing.

  Currently, I am just spawning threads and calling ffmpeg via subprocess module in Python. When I use subprocess.Popen() I quickly get memory errors because too many threads get started. Using subprocess.call() works error-free. Additionally, I am using threading.Semaphore() to limit maximum number of working threads.

  Code :

  import threading
  
  import subprocess
  
  
  
  maxthreads = 50
  
  sema = threading.Semaphore(value=maxthreads)
  
  threads = []
  
  
  
  def task(mp3_path):  # mp3 file path taken from the list of file_ids `mp3_list` below
  
      sema.acquire()
  
      subprocess.call(['ffmpeg', '-y',  '-i', mp3_path, '-preset', 'ultrafast', '-ar', '8000', wav_file_path])
  
      # provide file path and destination path
  
      sema.release()
  
  
  
  
  
  def conv_to_wav_():
  
      for i in mp3_list:
  
          thread = threading.Thread(target=task,args=([i]))
  
          threads.append(thread)
  
          thread.start()

  I am working on Windows 10 and have a CUDA-enabled Nvidia GPU available as well, if that’s helpful.