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• Use ffmpeg to cut out the first chapter

  7 janvier 2017, par UnR34L

  I’m trying to remove the first chapter of a TV show rip. The idea is to have something similar to netflix, where the first episode will show the intro then the consecutive episodes don’t.

  I’ve been getting the chapter time with ffprobe then doing it manually with this

  for %%A IN (*.mp4) DO ffmpeg -ss <chaptertime> -i "%%A" -vcodec copy -acodec copy "tmp.mp4" &amp;&amp; DEL "%%A" &amp;&amp; RENAME "tmp.mp4" "%%A"
  
  </chaptertime>

  How do I pass the first chapter time code value so ffmepg knows where to seek to ?

  Also hoping to use the same the same value to offset the subtitles so they align after the cut.

  Note : The machine I’ve doing the cutting on is windows but I can use my FreeBSD server if that’s easier.

• Non-RSA TLS1.2 Packet decryption

  7 février 2017, par Joseph Wahba

  I am trying to decrypt a pcap file. This pcap file contains a capture of an HLS encrypted video stream. The pcap contains TLSv1.2 packets.

  Below are some information from the pcap file

  Server Hello message Cipher Suite :

  TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384.

  EC Diffie-Hellman server Params : pubkey (1)

  The Certificate Status message :

  Signature Hash Algorithm Hash : SHA256

  Signature Hash Algorithm Signature : ECDSA

  Client Key Exchange Message

  EC Diffie-Hellman server Params : pubkey (2)

  I tried to follow this Wireshark SSL decryption tutorial. But it seems that it works only for RSA encryptions.
  I have been researching for a while and found this discussion. I am quoting an extract from this discussion :

  There is an important parameter to mind : decryption of a passively
  recorded session (with a copy of the server private key) works only if
  the key exchange was of type RSA or static DH ; with "DHE" and "ECDHE"
  cipher suites, you won’t be able to decrypt such a session, even with
  knowledge of the server private key. In that case, you will need
  either the negotiated "master secret", or to use the server private
  key to actively intercept the connection

  It’s note worthy that I have the client private key. In my case, the client is FFmpeg video streamer (FFplay). I had a look also on the TLS v1.2 RFC.

  My question :

  Is it possible to do a decryption in this scenario ? If yes, what do I need to have to do so ?

  Is the decryption done using the client’s private key or using the pre_shared_master (i.e. Diffie-Hellman) ?

• How can I skip an image error when trimming an mp3 with ffmpeg

  29 septembre 2016, par John Pollard

  I am running the following command to get cut a 30 second section of the file

  ffmpeg -i 'river.mp3' -ss 30 -t 30 -acodec libmp3lame -b:a 128k 'audio_trimmed.mp3'

  but I am getting a "Invalid PNG signature" error. Is there a way to skip the image since I don’t need it and have the command run successfully ?

  ffmpeg version 2.8.5 Copyright (c) 2000-2016 the FFmpeg developers
  
    built with Apple LLVM version 7.3.0 (clang-703.0.31)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.8.5 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libvorbis --enable-vda
  
    libavutil      54. 31.100 / 54. 31.100
  
    libavcodec     56. 60.100 / 56. 60.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 40.101 /  5. 40.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100
  
  [mp3 @ 0x7f8419010600] Skipping 0 bytes of junk at 73436.
  
  [png @ 0x7f8419812600] Invalid PNG signature 0xFFD8FFE000104A46.
  
  [mp3 @ 0x7f8419010600] decoding for stream 1 failed
  
  [mp3 @ 0x7f8419010600] Could not find codec parameters for stream 1 (Video: png, none(pc)): unspecified size
  
  Consider increasing the value for the 'analyzeduration' and 'probesize' options
  
  Input #0, mp3, from 'river.mp3':
  
    Metadata:
  
      genre           : Podcast
  
      album           : River City Church's Podcast
  
      artist          : Antley Fowler
  
      title           : Jubilee Brings Justice
  
      date            : 2016-08-15 10:23
  
    Duration: 00:28:28.07, start: 0.025056, bitrate: 64 kb/s
  
      Stream #0:0: Audio: mp3, 44100 Hz, mono, s16p, 64 kb/s
  
      Stream #0:1: Video: png, none(pc), 90k tbr, 90k tbn, 90k tbc
  
      Metadata:
  
        title           : Episode Artwork
  
        comment         : Cover (front)
  
  [buffer @ 0x7f8418c18de0] Unable to parse option value "0x0" as image size
  
  [buffer @ 0x7f8418c18de0] Unable to parse option value "-1" as pixel format
  
  [buffer @ 0x7f8418c18de0] Unable to parse option value "0x0" as image size
  
  [buffer @ 0x7f8418c18de0] Error setting option video_size to value 0x0.
  
  [graph 0 input from stream 0:1 @ 0x7f8418c18ee0] Error applying options to the filter.
  
  Error opening filters!