Comparison FHD Video files 42MB vs 4.5MB

Hello,
I got two files, one original 42MB and other is proccessed/modified size 4.5MB
Both file has same size and duration of video.

Looks like GOP was changed from fixed to Variable.

came across this when exchanging video samples, There is no information on what software was used to achive this.

Need help in understanding what changed and possible way to achive this using any of open source tools (Using Shotcut or gstreamer).

Please find report below

Original file:

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4
Format settings : CABAC / 3 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 3 frames
Format settings, GOP : M=1, N=15
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 min 4 s
Bit rate : 5589 kb/s
Width : 1920 pixels
Height : 1080 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 15.016 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.180
Stream size : 42.7 MiB (100%)

Processed File:

Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L4
Format settings : CABAC / 2 Ref Frames
Format settings, CABAC : Yes
Format settings, Reference frames : 2 frames
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 1 min 4 s
Bit rate : 597 kb/s
Width : 1920 pixels
Height : 1080 pixels
Display aspect ratio : 16:9
Frame rate mode : Variable
Frame rate : 15.016 FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bits
Scan type : Progressive
Bits/(Pixel*Frame) : 0.019
Stream size : 4.59 MiB (100%)

The bitrate is different… 5589 kbps in the original file versus 597 kbps in the processed file. That’s a 10x difference in bitrate, which accounts for a 10x difference in final file size.

There are two ways to decrease file size through lower bitrate:

  • Process the video in constant bitrate mode at a rate that is lower than the original.
  • Process the video in variable bitrate mode at a lower quality CRF than the original.

However, the lower bitrate usually implies a drop in visual quality. Whether the drop is significant enough to be noticed or bothersome is a call that you would have to individually make.

Edge case: If the original video was encoded as all-intra (All-I or GOP 1), then encoding a new file with Long GOP (such as 120 or higher) could enable major file size reduction without necessarily impacting quality, simply because the compression method is far more efficient.