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Help with determining if 45min MPG video has been spliced

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Help with determining if 45min MPG video has been spliced

Postby dreuxzer » Thu Apr 06, 2017 6:58 pm

Greetings from Lawrence, KS everyone!

I've got a 45min MPG dashcam video file of a traffic stop on a major highway here in Kansas. There is noticeable discontinuity at one particular point 30min in...we are trying to prove deliberate impropriety by law enforcement who have allegedly edited the video provided. I've used the ffprobe -show_frames with a dump [ > ] command to frames.txt. The process eventually completes but shows the following errors (which I'm hoping is indicative of the data we are seeking in this matter). Can anyone please help in determining what this output means? Many thanks, in advance!

Code: Select all
C:\Temp\ffmpeg\bin>ffprobe title06.mpg -show_frames > frames.txt
ffprobe version N-85266-g1229007 Copyright (c) 2007-2017 the FFmpeg developers
  built with gcc 6.3.0 (GCC)
  configuration: --enable-gpl --enable-version3 --enable-cuda --enable-cuvid --enable-d3d11va --enable-dxva2 --enable-libmfx --enable-nvenc --enable-avisynth --enable-bzlib --enable-fontconfig --enable-frei0r --enable-gnutls --enable-iconv --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libfreetype --enable-libgme --enable-libgsm --enable-libilbc --enable-libmodplug --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenh264 --enable-libopenjpeg --enable-libopus --enable-librtmp --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvo-amrwbenc --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxavs --enable-libxvid --enable-libzimg --enable-lzma --enable-zlib
  libavutil      55. 59.100 / 55. 59.100
  libavcodec     57. 90.100 / 57. 90.100
  libavformat    57. 72.100 / 57. 72.100
  libavdevice    57.  7.100 / 57.  7.100
  libavfilter     6. 83.100 /  6. 83.100
  libswscale      4.  7.100 /  4.  7.100
  libswresample   2.  8.100 /  2.  8.100
  libpostproc    54.  6.100 / 54.  6.100
Input #0, mpeg, from 'title06.mpg':
  Duration: 00:47:56.40, start: 0.049522, bitrate: 1470 kb/s
    Stream #0:0[0x1bf]: Data: dvd_nav_packet
    Stream #0:1[0x1c0]: Audio: mp2, 48000 Hz, stereo, s16p, 384 kb/s
    Stream #0:2[0x1e0]: Video: mpeg2video (Main), yuv420p(tv, top first), 352x480 [SAR 20:11 DAR 4:3], Closed Captions, 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
Unsupported codec with id 100357 for input stream 0
[mp2 @ 000000000070cde0] Header missing
    Last message repeated 1 times
overread 9
[mpeg2video @ 000000000070c5c0] Warning MVs not available
[mpeg2video @ 000000000070c5c0] concealing 506 DC, 506 AC, 506 MV errors in P frame
[mp2 @ 000000000070cde0] Header missing
    Last message repeated 10 times
[mpeg2video @ 000000000070c5c0] mb incr damaged
[mpeg2video @ 000000000070c5c0] Warning MVs not available
[mpeg2video @ 000000000070c5c0] concealing 22 DC, 22 AC, 22 MV errors in P frame
[mp2 @ 000000000070cde0] Header missing
    Last message repeated 2 times
[mpeg2video @ 000000000070c5c0] ac-tex damaged at 10 23
[mpeg2video @ 000000000070c5c0] Warning MVs not available
[mpeg2video @ 000000000070c5c0] concealing 22 DC, 22 AC, 22 MV errors in P frame
[mp2 @ 000000000070cde0] Header missing
    Last message repeated 1 times
[mpeg2video @ 000000000070c5c0] 00 motion_type at 15 22
[mpeg2video @ 000000000070c5c0] Warning MVs not available
[mpeg2video @ 000000000070c5c0] concealing 22 DC, 22 AC, 22 MV errors in B frame

C:\Temp\ffmpeg\bin>


Kindest regards,

Dreux of Private Digital Investigators, LLC
dreuxzer
 
Posts: 3
Joined: Thu Apr 06, 2017 6:46 pm

Re: Help with determining if 45min MPG video has been splice

Postby mulvya » Fri Apr 07, 2017 4:04 pm

Those missing motion vector errors could indicate missing frames if they occur in the middle of the stream. But it's also possible they are from start of the stream if these segment was chopped off from a longer video.

Try

Code: Select all
ffmpeg -ss 1700 -i title06.mpg -c copy title06-ss1700.mpg


and then

Code: Select all
ffprobe title06-ss1700.mpg -show_frames > frames.txt


The first command extracts the audio/video starting at the nearest keyframe before t=1700 seconds. The 2nd command is to see if the same decoding error messages are shown.

You can also run

Code: Select all
ffmpeg -t 1700 -i title06.mpg -c copy title06-t1700.mpg


to extract upto t=1700 seconds and check that.
mulvya
 
Posts: 570
Joined: Mon Oct 26, 2015 6:58 am

Re: Help with determining if 45min MPG video has been splice

Postby dreuxzer » Fri Apr 07, 2017 7:28 pm

Excellent! Thanks very much for the quick response...I will run the suggested commands and report back with my findings.
dreuxzer
 
Posts: 3
Joined: Thu Apr 06, 2017 6:46 pm


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