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• Python convert binary data (str) to match multiple of float32 size

  15 avril 2016, par Kendall Weihe

  I’m working on a tensorflow project, and I’m working with raw data from a mp3 file. I’m using FFMPEG and capturing STDOUT. FFMPEG outputs binary data in type str but it doesn’t capture the data in a multiple of the size of a float32 ...or apparently that’s what I am assuming from the error I get from the following code...

  import subprocess as sp
  
  command = ["ffmpeg",
  
          '-i', image_file,
  
          '-f', 's16le',
  
          '-acodec', 'pcm_s16le',
  
          '-ar', '44100', # ouput will have 44100 Hz
  
          '-ac', '2', # stereo (set to '1' for mono)
  
          '-']
  
  pipe = sp.Popen(command, stdout=sp.PIPE, stderr=sp.STDOUT, stdin=sp.PIPE)
  
  raw_audio, _  = pipe.communicate(str(88200*4).encode())
  
  audio_array = np.fromstring(raw_audio, dtype="float32") //ERROR
  
  
  
  dataset = np.append(dataset,audio_array)

  Error

  File "main.py", line 68, in maybe_pickle
  
    audio_array = np.fromstring(raw_audio, dtype="float32")
  
  ValueError: string size must be a multiple of element size

  raw_audio is in the form :

  ...7k\x01t\xf9\xc3\x01\xe3\xfa\x11\x02\xfb\xfb~\xff\x90\xfb\xbb\xfc\x83\xfa\xb4\xfd\xde\xfb\xab\xff\x01\xff\xd4\xfe:\x00T\xfd\xe0\xff\xae\xfdV\x01\xd8\xfd\x1a\x04\x0f\xfcR\x05,\xfaG\x05\xb1\xfaD\x05\xa1\xfdP\x04e\x00\xbc\x01\xe6\x00\xdf\xfe`\x00\x16\xfd\xae\x00\xec\xfc\xb7\x00\x7f\...

  Is there a way I can truncate the data ? Or maybe capture the string in an entirely different way ?

• How can I reencode a video to match another's codec exactly ?

  24 janvier 2020, par Stephen Schrauger

  When I’m on vacation, I usually use our camcorder to record videos. Since they’re all the same format, I can use ffmpeg to concat them into one large, smooth video without re-encoding.

  However, sometimes I will use a phone or other camera to record a video (if the camcorder ran out of space/battery or was left at a hotel).

  I’d like to determine the codec, framerate, etc used by my camcorder and use those parameters to convert the phone vidoes into the same format. That way, I will be able to concatonate all the videos without re-encoding the camcorder videos.

  Using ffprobe, I found my camcorder has this encoding :

    Input #0, mpegts, from 'camcorderfile.MTS':
  
    Duration: 00:00:09.54, start: 1.936367, bitrate: 24761 kb/s
  
    Program 1 
  
      Stream #0:0[0x1011]: Video: h264 (High) (HDPR / 0x52504448), yuv420p(progressive), 1920x1080 [SAR 1:1 DAR 16:9], 59.94 fps, 59.94 tbr, 90k tbn, 119.88 tbc
  
      Stream #0:1[0x1100]: Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz, stereo, fltp, 256 kb/s
  
      Stream #0:2[0x1200]: Subtitle: hdmv_pgs_subtitle ([144][0][0][0] / 0x0090), 1920x1080

  The phone (iPhone 5s) encoding is :

    Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'mov.MOV':
  
    Metadata:
  
      major_brand     : qt  
  
      minor_version   : 0
  
      compatible_brands: qt  
  
      creation_time   : 2017-01-02T03:04:05.000000Z
  
      com.apple.quicktime.location.ISO6709: +12.3456-789.0123+456.789/
  
      com.apple.quicktime.make: Apple
  
      com.apple.quicktime.model: iPhone 5s
  
      com.apple.quicktime.software: 10.2.1
  
      com.apple.quicktime.creationdate: 2017-01-02T03:04:05-0700
  
    Duration: 00:00:14.38, start: 0.000000, bitrate: 11940 kb/s
  
      Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 11865 kb/s, 29.98 fps, 29.97 tbr, 600 tbn, 1200 tbc (default)
  
      Metadata:
  
        creation_time   : 2017-01-02T03:04:05.000000Z
  
        handler_name    : Core Media Data Handler
  
        encoder         : H.264
  
      Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 63 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-01-02T03:04:05.000000Z
  
        handler_name    : Core Media Data Handler
  
      Stream #0:2(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-01-02T03:04:05.000000Z
  
        handler_name    : Core Media Data Handler
  
      Stream #0:3(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
  
      Metadata:
  
        creation_time   : 2017-01-02T03:04:05.000000Z
  
        handler_name    : Core Media Data Handler

  I’m presuming that ffmpeg will automatically take any acceptable video format, and that I only need to figure out the output settings. I think I need to use -s 1920x1080 and -pix_fmt yuv420p for the output, but what other flags do I need in order to make the phone video into the same encoding as the camcorder video ?

  Can I get some pointers as to how I can translate the ffprobe output into the flags I need to give to ffmpeg ?

  Edit : Added the entire Input #0 for both media files.

• Revision 6c280c2299 : Adjust style to match Google Coding Style a little more closely. Most of these

  1er novembre 2012, par Ronald S. Bultje

  Changed Paths : Modify /vp8/common/arm/arm_systemdependent.c Modify /vp8/common/debugmodes.c Modify /vp8/common/entropymode.c Modify /vp8/common/entropymode.h Modify /vp8/common/extend.c Modify /vp8/common/extend.h Modify /vp8/common/filter.c (...)