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• CCTV DVR recovery

  5 juin 2014, par bitmadmax

  I need to recover footage from one of these unbranded CCTV DVR units. I am unable to gain access to the unit via a password, factory reset or backdoor, which would otherwise have let me "export" the footage.

  So I have pulled the hard disk and made a copy of it. The original unit is Linux-based which ran off a chip, and an EXT filesystem laid down on the hard disk itself. There is one partition which appears to contain the "raw" CCTV footage.

  The hex structure appears as though each frame begins with 00dcH264, 01dcH264, 10dcH264 and so on... I think the 00, 01, 10 etc refers to the channel/camera input number. The hex contents after the H264 portion appears completely random, of variable length and has no signature, and is followed immediately with the next xxdcH264 header.

  When I use ffprobe across the entire raw footage partition, it is only detecting the 1 video stream. I can use ffmpeg to "force" it to read it in as H.264 and dump it out into an MP4 file that I can play. However, this gives me the problem that the footage as an individual file is quite "noisy" and has frames from each channel appearing randomly.

  Is there anyway I could maybe separate out the footage into say a file for each channel ? I am not a great programmer so something as simple as possible would be ideal. I did note that ffprobe determined that some of the frames were of different resolution - it is likely that the different channels recorded their image at different dimensions, I just wondered if another way might be to get ffprobe/ffmpeg to output frames based on their image dimensions perhaps ?

  EDIT : sample hex below :

  Offset      0  1  2  3  4  5  6  7   8  9 10 11 12 13 14 15
  
  00000000   32 31 64 63 48 32 36 34  76 08 00 00 00 00 00 00   21dcH264v       
  
  00000016   1E 8B 77 07 6A 00 00 00  00 00 00 01 61 FC 03 51    ‹w j       aü Q
  
  00000032   42 83 FC C5 C6 BD 50 63  5F 37 68 B6 B5 B8 4F E0   BƒüÅƽPc_7h¶µ¸Oà
  
  00000048   2E 74 B8 FF BB BD 70 1C  DE 1E 7A 8C 0F            .t¸ÿ»½p Þ zŒ 

  (variable length)....

  Offset      0  1  2  3  4  5  6  7   8  9 10 11 12 13 14 15
  
  00000000   D3 30 59 01 FA 98 08 A0  0A 27 01 49 19 C1 0C 89   Ó0Y ú˜   ' I Á ‰
  
  00000016   83 AC 6B 28 03 8D 92 29  38 18 BA 95 82 B3 BA C6   ƒ¬k(  ’)8 º•‚³ºÆ
  
  00000032   33 0A 74 10 1A D5 89 3B  90 A0 19 1F A9 93 00 10   3 t  Õ‰;    ©“  
  
  00000048   92 AA 70 32 31 64 63 48  32 36 34                  ’ªp21dcH264

• FFMPEG.wasm Cannot Add Album Cover To MP3 File

  5 juillet 2022, par Shaan Khan

  for a project I'm working on I'm trying to split a video into multiple audio clips whilst adding metadata for each individual track. Whilst doing this, whilst I've added most of the metadata including title & artist, I'm unable to add an album cover via FFMPEG.wasm. Whilst my command works fine with regular FFMPEG.wasm, I'm unable to get it to work via the webassembly version.

  


  I'm aware that my album cover is correctly being assigned via FS.readfile and that my command in theory should work, but I'm unable to figure out why it isn't working. Is this a FFMPEG.wasm limitation and if so, is there any workaround for this ?

  


  

  • Normal FFMPEG Command

  


  


  ffmpeg -i "song.mp3" -i albumCover.jpg -map 0:0 -map 1:0 -y -codec:a libmp3lame -ac 2 -ar 48000 -ab 320k -ss 00:00:00 -t 00:00:20 -id3v2_version 3  -metadata title="SongOne" -metadata album_artist="Artist Name" -metadata album="Youtube Name" -metadata track="1" "output.mp3"


  


  

  • FFMPEG WASM Implementation

  


  


    let commandArray = [
      "-i",
      "song.mp3",
      "-i",
      "albumCover.jpg",
      "-map",
      "0:0",
      "-map",
      "1:0",
      "-y",
      "-codec:a",
      "libmp3lame",
      "-ac",
      "2",
      "-ar",
      "48000",
      "-ab",
      "320k",
      "-ss",
      startTime.toString(),
    ];

    if (duration != "-1") {
      commandArray.push("-t", duration.toString());
    }

    commandArray.push(
      "-id3v2_version",
      "3",
      "-metadata",
      `title="${title}"`,
      "-metadata",
      `album_artist="${artist}`,
      "-metadata",
      `album="${albumInfo.name}"`,
      "-metadata",
      `track="1"`,
      `${timestamp.songName} - ${timestamp.artistName}.mp3`
    );


  


• Concatenate two files while keeping the duration the same as the two files separately

  21 septembre 2020, par John Pollard

  When I calculate the duration of each individual file I want to concatenate I get 10.24 for both. So I figured when I concatenate the two files I would get a duration of file A plus file B or 10.24 + 10.24 giving me a total duration of 20.48 for the combined file. But no matter what command I use to concentrate I cannot get the same duration. Am I doing something wrong ?

  


  ffprobe -i "audioA.mp3" -show_entries format=duration -v quiet -of csv="p=0"
10.24 


  


  ffprobe -i "audioB.mp3" -show_entries format=duration -v quiet -of csv="p=0"
10.24 


  


  Which makes a total of 10.24 + 10.24 = 20.48 seconds

  


  But when I concatenate the files I get a different duration. Here are my different tries.

  


  Try 1

  


  FFMPEG -y -i 'concat:audioA.mp3|audioB.mp3' -map 0:a -codec:a copy -map_metadata -1 output.mp3
ffprobe -i "output.mp3" -show_entries format=duration -v quiet -of csv="p=0"
20.610612


  


  Try 2

  


  FFMPEG -y -i audioA.mp3 -i audioB.mp3 -filter_complex [0:a][1:a]concat=n=2:v=0:a=1 output.mp3
ffprobe -i "output.mp3" -show_entries format=duration -v quiet -of csv="p=0
20.453878


  


  Try 3

  


  FFMPEG -y -i 'concat:audioA.mp3|audioB.mp3' output.mp3
ffprobe -i "output.mp3" -show_entries format=duration -v quiet -of csv="p=0"
20.506122


  


  

  • Is there a command to use to concatenate that will output a file with
the same duration ?

  


  • Is there a way to do that without reencoding ?

  


  • What makes the durations different in the combined files above ?