Recherche avancée

Sur d’autres sites (11405)

• How can I retain 2x pixel density when encoding Retina screen capture with ffmpeg ?

  26 février 2018, par hfossli

  Whenever I use ffmpeg to encode a HiDPI/Retina screen recording, the video plays at 2x the size, so it looks fuzzy, because the pixel density is not retained.

  How can I retain the original pixel density of HiDPI screen recordings with ffmpeg ?

  How to reproduce :

  1. Use QuickTime Player to create a Screen Recording on a Retina Mac.
  2. Play the video you recorded in QuickTime Player using the ⌘1 Actual Size view. Notice that it’s playing 2:1 on your Retina Display, so the video looks sharp. It’s playing in half the space of the actual recorded pixels.

  3. Use ffmpeg to encode the video using a command like this :

     ffmpeg -i haha.mov -c:v libx264 -crf 23 haha-lg.mov

  4. Play the new ffmpeg-compressed video in QuickTime Player using the ⌘1 Actual Size view. Notice that it’s playing 1:1, so the video looks fuzzy.

  To clarify, the video does not look blurry because it was compressed. Rather, it looks blurry because the video is being played twice as big as it should be, at a 1:1 pixel density, instead of the required 2:1 pixel density, presumably because some metadata is being discarded when encoding.

  For the record, VLC plays both videos too big (blurry). So being able to play HiDPI videos seems to be a feature of QuickTime Player.

  Here is the detailed information ffmpeg shows for the original screen recording :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'haha.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2018-02-26T16:46:00.000000Z
  
      com.apple.quicktime.make: Apple
  
      com.apple.quicktime.model: iMac18,3
  
      com.apple.quicktime.software: Mac OS X 10.13.3 (17D102)
  
      com.apple.quicktime.creationdate: 2018-02-26T10:45:50-0600
  
    Duration: 00:00:04.35, start: 0.000000, bitrate: 10947 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1396x928 [SAR 1:1 DAR 349:232], 10701 kb/s, 60 fps, 60 tbr, 6k tbn, 12k tbc (default)
  
      Metadata:
  
        creation_time   : 2018-02-26T16:46:00.000000Z
  
        handler_name    : Core Media Data Handler
  
        encoder         : H.264

  And here is the information for the ffmpeg-compressed version :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'haha-lg.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 512
  
      compatible_brands: qt  
  
      encoder         : Lavf57.83.100
  
    Duration: 00:00:04.35, start: 0.000000, bitrate: 1923 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1396x928 [SAR 1:1 DAR 349:232], 1783 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc (default)
  
      Metadata:
  
        handler_name    : DataHandler
  
        encoder         : Lavc57.107.100 libx264

• How can I retain 2x pixel density when encoding Retina screen capture with ffmpeg ?

  26 février 2018, par hfossli

  Whenever I use ffmpeg to encode a HiDPI/Retina screen recording, the video plays at 2x the size, so it looks fuzzy, because the pixel density is not retained.

  How can I retain the original pixel density of HiDPI screen recordings with ffmpeg ?

  How to reproduce :

  1. Use QuickTime Player to create a Screen Recording on a Retina Mac.
  2. Play the video you recorded in QuickTime Player using the ⌘1 Actual Size view. Notice that it’s playing 2:1 on your Retina Display, so the video looks sharp. It’s playing in half the space of the actual recorded pixels.

  3. Use ffmpeg to encode the video using a command like this :

     ffmpeg -i haha.mov -c:v libx264 -crf 23 haha-lg.mov

  4. Play the new ffmpeg-compressed video in QuickTime Player using the ⌘1 Actual Size view. Notice that it’s playing 1:1, so the video looks fuzzy.

  To clarify, the video does not look blurry because it was compressed. Rather, it looks blurry because the video is being played twice as big as it should be, at a 1:1 pixel density, instead of the required 2:1 pixel density, presumably because some metadata is being discarded when encoding.

  For the record, VLC plays both videos too big (blurry). So being able to play HiDPI videos seems to be a feature of QuickTime Player.

  Here is the detailed information ffmpeg shows for the original screen recording :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'haha.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2018-02-26T16:46:00.000000Z
  
      com.apple.quicktime.make: Apple
  
      com.apple.quicktime.model: iMac18,3
  
      com.apple.quicktime.software: Mac OS X 10.13.3 (17D102)
  
      com.apple.quicktime.creationdate: 2018-02-26T10:45:50-0600
  
    Duration: 00:00:04.35, start: 0.000000, bitrate: 10947 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1396x928 [SAR 1:1 DAR 349:232], 10701 kb/s, 60 fps, 60 tbr, 6k tbn, 12k tbc (default)
  
      Metadata:
  
        creation_time   : 2018-02-26T16:46:00.000000Z
  
        handler_name    : Core Media Data Handler
  
        encoder         : H.264

  And here is the information for the ffmpeg-compressed version :

  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'haha-lg.mov':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 512
  
      compatible_brands: qt  
  
      encoder         : Lavf57.83.100
  
    Duration: 00:00:04.35, start: 0.000000, bitrate: 1923 kb/s
  
      Stream #0:0(eng): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1396x928 [SAR 1:1 DAR 349:232], 1783 kb/s, 60 fps, 60 tbr, 15360 tbn, 120 tbc (default)
  
      Metadata:
  
        handler_name    : DataHandler
  
        encoder         : Lavc57.107.100 libx264

• FFMPEG command from Python 3.5 does not actually create audio file

  20 décembre 2017, par Nathan Blaine

  I have a Django web application that accepts user uploaded videos/audio and saves them into a folder ’../WebAppDirectory/media/recordings’.

  I am then using a speech to text API to get a rough transcription of the audio. This is working fine for .wav and .mp4 files, but the web app also accepts videos (.MOV) that I would like to first convert to .wav, then pass off to the API.

  Using ffmpeg from my command line like this

  ffmpeg -i C:\Users\Nathan\Desktop\MeetingRecorderWebAPP\media\recordings\upload_sample.MOV -ab 160k -ac 2 -ar 44100 -vn upload_sample.wav

  Correctly creates the .wav file from the original .MOV.

  However, when I run this from python with

  subprocess.check_call(command, shell=True)

  ffmpeg responds with

  File ’upload_sample.wav’ already exists. Overwrite ? [y/N]

  While Python tells me

  FileNotFoundError : [Errno 2] No such file or directory : ’C :\Users\Nathan\Desktop\MeetingRecorderWebAPP\media\recordings\upload_sample.wav’

  It is also worth noting that I do not see a ’upload_sample.wav’ file in the media/recordings/ directory.

  This leads me to believe that maybe Python and ffmpeg are looking in different folders, but I am not sure where I am going wrong. When I print the command from the subprocess.check_call and copy/paste it into cmd, the file is created as expected.

  Hoping someone with some experience with ffmpeg/Python subprocess can help shed some light ! Here are the files I am working with :

  Folder Structure

  DjangoWebApp
  
  |---media
  
  |---|---imgs
  
  |---|---recordings
  
  |---|---|---upload_sample.MOV
  
  |---uploaded_audio_to_text.py

  uploaded_audio_to_text.py

  import speech_recognition as sr
  
  from os import path
  
  import os
  
  import subprocess
  
  
  
  
  
  def speech_to_text(file_name):
  
      AUDIO_FILE = path.join(path.dirname(path.realpath(__file__)), 'media','recordings', file_name)
  
      print("Looking at path: ",AUDIO_FILE)
  
      # get extension
  
      AUDIO_FILE_EXT = os.path.splitext(AUDIO_FILE)[1]
  
  
  
      if(AUDIO_FILE_EXT == '.MOV'):
  
          print("File is not .wav: ", AUDIO_FILE_EXT, "found. Converting...")
  
          # We will use subprocess and ffmpeg to convert this .MOV file to .wav, so we can send to API
  
          temp_wav = os.path.splitext(file_name)[0] + '.wav'
  
          print("New audio file will be: ", temp_wav)
  
          # build CMD ffmpeg command
  
          command = "ffmpeg -i "
  
          command += AUDIO_FILE
  
          command += " -ab 160k -ac 2 -ar 44100 -vn "
  
          command += temp_wav
  
  
  
          print("Attempting to run this command: \n",command)
  
          print(subprocess.check_call(command, shell=True))
  
          print("Past Subprocess.call")
  
          AUDIO_FILE = path.join(path.dirname(path.realpath(__file__)), 'media','recordings', temp_wav)
  
          print("AUDIO_FILE now set to: ", AUDIO_FILE)
  
  
  
      else:
  
          # continue with what we are doing
  
          pass
  
  
  
  
  
      r = sr.Recognizer()
  
      with sr.AudioFile(AUDIO_FILE) as source:
  
          audio = r.record(source)  # read the entire audio file
  
          text_transcription = "Sentinel"
  
          # recognize speech using Microsoft Bing Voice Recognition
  
          BING_KEY = "MY_KEY_:)"
  
          try:
  
              text_transcription = r.recognize_bing(audio, key=BING_KEY)
  
          except sr.UnknownValueError:
  
              print("Microsoft Bing Voice Recognition could not understand audio")
  
          except sr.RequestError as e:
  
              print("Could not request results from Microsoft Bing Voice Recognition service; {0}".format(e))
  
  
  
      return text_transcription
  
  
  
  
  
  #my tests
  
  my_relative_file_path = "upload_sample.MOV"
  
  print(speech_to_text(my_relative_file_path))

  Console output (traceback and my print()’s)

  Looking at path:  C:\Users\Nathan\Desktop\MeetingRecorderWebAPP\media\recordings\upload_sample.MOV 
  
  File is not .wav:  .MOV found. Converting... 
  
  New audio file will be:  upload_sample.wav Attempting to run this command:
  
   ffmpeg -i C:\Users\Nathan\Desktop\MeetingRecorderWebAPP\media\recordings\upload_sample.MOV -ab 160k -ac 2 -ar 44100 -vn upload_sample.wav 
  
  ffmpeg version git-2017-12-18-74f408c Copyright (c) 2000-2017 the FFmpeg developers   built with gcc 7.2.0 (GCC)   
  
  ----REMOVED SOME FFMPEG OUTPUT FOR BREVITY----
  
  File 'upload_sample.wav' already exists. Overwrite ? [y/N] y 
  
  Stream mapping:   Stream #0:1 -> #0:0 (aac (native) -> pcm_s16le (native)) Press [q] to stop, [?] for help Output #0, wav, to 'upload_sample.wav':   Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      com.apple.quicktime.creationdate: 2017-12-19T16:06:10-0500
  
      com.apple.quicktime.make: Apple
  
      com.apple.quicktime.model: iPhone 6
  
      com.apple.quicktime.software: 10.3.3
  
      ISFT            : Lavf58.3.100
  
      Stream #0:0(und): Audio: pcm_s16le ([1][0][0][0] / 0x0001), 44100 Hz, stereo, s16, 1411 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-12-19T21:06:11.000000Z
  
        handler_name    : Core Media Data Handler
  
        encoder         : Lavc58.8.100 pcm_s16le size=    1036kB time=00:00:06.01 bitrate=1411.3kbits/s speed=N/A     video:0kB audio:1036kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.007352% 
  
  0 
  
  Traceback (most recent call last): Past Subprocess.call   
  
  File "C:\Users\Nathan\Desktop\MeetingRecorderWebAPP\uploaded_audio_to_text.py", line 53, in <module> 
  
  AUDIO_FILE now set to:  C:\Users\Nathan\Desktop\MeetingRecorderWebAPP\media\recordings\upload_sample.wav
  
      print(speech_to_text(my_relative_file_path))   
  
  File "C:\Users\Nathan\Desktop\MeetingRecorderWebAPP\uploaded_audio_to_text.py", line 36, in speech_to_text
  
      with sr.AudioFile(AUDIO_FILE) as source:   
  
  File "C:\Users\Nathan\AppData\Local\Programs\Python\Python36-32\lib\site-packages\speech_recognition\__init__.py", line 203, in __enter__
  
      self.audio_reader = wave.open(self.filename_or_fileobject, "rb")   
  
  File "C:\Users\Nathan\AppData\Local\Programs\Python\Python36-32\lib\wave.py", line 499, in open
  
      return Wave_read(f)   
  
  File "C:\Users\Nathan\AppData\Local\Programs\Python\Python36-32\lib\wave.py", line 159, in __init__
  
      f = builtins.open(f, 'rb') 
  
  FileNotFoundError: [Errno 2] No such file or directory: 'C:\\Users\\Nathan\\Desktop\\MeetingRecorderWebAPP\\media\\recordings\\upload_sample.wav'
  
  
  
  Process finished with exit code 1
  
  </module>