Cutting AVI into four parts seems to have lost footage

[kingmustard123]

I have a 1h 12m 19s AVI file that I recorded / captured from my Canon MD101 back in 2008. The file is 12.9 GB.

I have used Avidemux to cut it into quarters, as 12.9 GB is quite a large file.

However, the four new files total 1h 12m 13s.

I do not believe there are any keyframes to worry about, so I am a bit confused.

Any ideas?

If it helps, here is the data from MediaInfo of the original file, and one of the cut files:

Original:

General
Format                                   : AVI
Format/Info                              : Audio Video Interleave
Commercial name                          : DVCAM
Format profile                           : OpenDML
Format settings                          : BitmapInfoHeader / PcmWaveformat
File size                                : 13.0 GiB
Duration                                 : 1 h 2 min
Overall bit rate mode                    : Constant
Overall bit rate                         : 29.8 Mb/s
Frame rate                               : 25.000 FPS
Recorded date                            : 2008-06-19 19:58:28.000
Writing application                      : Adobe Premiere Pro 2.0

Video
ID                                       : 0
Format                                   : DV
Commercial name                          : DVCAM
Codec ID                                 : dvsd
Codec ID/Hint                            : Sony
Duration                                 : 1 h 2 min
Bit rate mode                            : Constant
Bit rate                                 : 24.4 Mb/s
Width                                    : 720 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 4:3
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Interlaced
Scan order                               : Bottom Field First
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 2.357
Stream size                              : 12.5 GiB (97%)
Encoding settings                        : wb mode= / white balance= / fcm=auto focus

Audio
ID                                       : 1
Format                                   : PCM
Format settings                          : Little / Signed
Codec ID                                 : 1
Duration                                 : 1 h 2 min
Bit rate mode                            : Constant
Bit rate                                 : 1 024 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 32.0 kHz
Bit depth                                : 16 bits
Stream size                              : 457 MiB (3%)
Alignment                                : Aligned on interleaves
Interleave, duration                     : 1000  ms (25.00 video frames)
Interleave, preload duration             : 1000  ms

Cut:

General
Format                                   : AVI
Format/Info                              : Audio Video Interleave
Commercial name                          : DVCAM
Format settings                          : BitmapInfoHeader / PcmWaveformat
File size                                : 3.09 GiB
Duration                                 : 14 min 49 s
Overall bit rate mode                    : Constant
Overall bit rate                         : 29.8 Mb/s
Frame rate                               : 25.000 FPS
Recorded date                            : 2008-06-19 19:58:28.000

Video
ID                                       : 0
Format                                   : DV
Commercial name                          : DVCAM
Codec ID                                 : dvsd
Codec ID/Hint                            : Sony
Duration                                 : 14 min 49 s
Bit rate mode                            : Constant
Bit rate                                 : 24.4 Mb/s
Width                                    : 720 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 4:3
Frame rate mode                          : Constant
Frame rate                               : 25.000 FPS
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Interlaced
Scan order                               : Bottom Field First
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 2.357
Stream size                              : 2.98 GiB (97%)
Encoding settings                        : wb mode= / white balance= / fcm=auto focus

Audio
ID                                       : 1
Format                                   : PCM
Format settings                          : Little / Signed
Codec ID                                 : 1
Duration                                 : 14 min 49 s
Bit rate mode                            : Constant
Bit rate                                 : 1 024 kb/s
Channel(s)                               : 2 channels
Sampling rate                            : 32.0 kHz
Bit depth                                : 16 bits
Stream size                              : 109 MiB (3%)
Alignment                                : Aligned on interleaves
Interleave, duration                     : 25  ms (0.63 video frame)

[videoAI]

There are a few potential reasons for the slight time discrepancy you're experiencing.

Possible Causes:

1- Keyframe Alignment
- Even if you don't think there are keyframes, video editing software often uses keyframe-based cutting

2- Codec Specifics
- Some codecs handle cutting differently, potentially losing a few seconds during segmentation

3- Metadata Inconsistency
- Avidemux might not perfectly preserve exact timestamps

Verification Steps
I recommend using ffprobe to get more precise information about the original and cut files.

# Check original file details

ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 original_file.avi

# Check cut file details

ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 cut_file1.avi
ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 cut_file2.avi
ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 cut_file3.avi
ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 cut_file4.avi

FFmpeg often provides more accurate cutting compared to Avidemux.

[jagabo]

Standard definition DV is all keyframes. You can cut in/out losslessly on any frame. So that's not an issue.