Filesize hardly decreases in shortened video (.mp4)

[NeighbouringPanda]

I shortened a 317MB video (.mp4) to about 81% of its original length and exported it in the same format.
But the new file got only about 5MB smaller??
I checked the file-properties, everything is the same, except:

• Duration changed from 01:53:00 to 01:32:00s (expected)
• Total Bitrate increased from 388KB/s to 469KB/s (so this makes the file bigger than it should i think)

Is this normal? I only want cut unused beginning/ending to decrease videos file size...
Is there any way to decrease size more efficiently without compression?

(discovered this tool just today)

[mifi]

how many tracks/streams does your file have? it would be helpful if you provide a report (help menu)

[NeighbouringPanda]

There are 2 i guess, in the Metadata-section it says:
0: audio mp4a aac - 1cmono
1: video avc1 h264 - 1600x800
2: / striked

The report:

No error

{
  "state": {
    "filePath": "C:\\Users\\XXX\\myVideo.mp4",
    "fileFormat": "mp4",
    "externalStreamFiles": [],
    "mainStreams": [
      {
        "index": 0,
        "codec_name": "aac",
        "codec_long_name": "AAC (Advanced Audio Coding)",
        "profile": "LC",
        "codec_type": "audio",
        "codec_time_base": "1/32000",
        "codec_tag_string": "mp4a",
        "codec_tag": "0x6134706d",
        "sample_fmt": "fltp",
        "sample_rate": "32000",
        "channels": 1,
        "channel_layout": "mono",
        "bits_per_sample": 0,
        "r_frame_rate": "0/0",
        "avg_frame_rate": "0/0",
        "time_base": "1/32000",
        "start_pts": 0,
        "start_time": "0.000000",
        "duration_ts": 218517504,
        "duration": "6828.672000",
        "bit_rate": "53374",
        "max_bit_rate": "130250",
        "nb_frames": "213396",
        "disposition": {
          "default": 1,
          "dub": 0,
          "original": 0,
          "comment": 0,
          "lyrics": 0,
          "karaoke": 0,
          "forced": 0,
          "hearing_impaired": 0,
          "visual_impaired": 0,
          "clean_effects": 0,
          "attached_pic": 0,
          "timed_thumbnails": 0
        },
        "tags": {
          "creation_time": "2020-10-01T05:38:42.000000Z",
          "language": "und",
          "handler_name": "AAC audio"
        }
      },
      {
        "index": 1,
        "codec_name": "h264",
        "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
        "profile": "High",
        "codec_type": "video",
        "codec_time_base": "1/50",
        "codec_tag_string": "avc1",
        "codec_tag": "0x31637661",
        "width": 1600,
        "height": 800,
        "coded_width": 1600,
        "coded_height": 800,
        "closed_captions": 0,
        "has_b_frames": 0,
        "pix_fmt": "yuv420p",
        "level": 50,
        "refs": 1,
        "is_avc": "true",
        "nal_length_size": "4",
        "r_frame_rate": "25/1",
        "avg_frame_rate": "25/1",
        "time_base": "1/30000",
        "start_pts": 0,
        "start_time": "0.000000",
        "duration_ts": 204861600,
        "duration": "6828.720000",
        "bit_rate": "334932",
        "bits_per_raw_sample": "8",
        "nb_frames": "170718",
        "disposition": {
          "default": 1,
          "dub": 0,
          "original": 0,
          "comment": 0,
          "lyrics": 0,
          "karaoke": 0,
          "forced": 0,
          "hearing_impaired": 0,
          "visual_impaired": 0,
          "clean_effects": 0,
          "attached_pic": 0,
          "timed_thumbnails": 0
        },
        "tags": {
          "creation_time": "2020-10-01T05:38:42.000000Z",
          "language": "und",
          "handler_name": "H.264/AVC video",
          "encoder": "AVC Coding"
        }
      },
      {
        "index": 2,
        "codec_name": "bin_data",
        "codec_long_name": "binary data",
        "codec_type": "data",
        "codec_tag_string": "text",
        "codec_tag": "0x74786574",
        "r_frame_rate": "0/0",
        "avg_frame_rate": "0/0",
        "time_base": "1/1000",
        "start_pts": 0,
        "start_time": "0.000000",
        "duration_ts": 6828720,
        "duration": "6828.720000",
        "nb_frames": "25",
        "disposition": {
          "default": 0,
          "dub": 0,
          "original": 0,
          "comment": 0,
          "lyrics": 0,
          "karaoke": 0,
          "forced": 0,
          "hearing_impaired": 0,
          "visual_impaired": 0,
          "clean_effects": 0,
          "attached_pic": 0,
          "timed_thumbnails": 0
        },
        "tags": {
          "creation_time": "2020-10-01T05:38:42.000000Z",
          "language": "und",
          "handler_name": "Text"
        }
      }
    ],
    "copyStreamIdsByFile": {
      "C:\\Users\\XXX\\myVideo.mp4": {
        "0": true,
        "1": true,
        "2": false
      }
    },
    "cutSegments": [
      {}
    ],
    "fileFormatData": {
      "filename": "C:\\Users\\XXX\\myVideo.mp4",
      "nb_streams": 3,
      "nb_programs": 0,
      "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
      "format_long_name": "QuickTime / MOV",
      "start_time": "0.000000",
      "duration": "6828.720000",
      "size": "333274177",
      "bit_rate": "390438",
      "probe_score": 100,
      "tags": {
        "major_brand": "mp42",
        "minor_version": "0",
        "compatible_brands": "isommp42",
        "creation_time": "2020-10-01T05:38:42.000000Z"
      }
    },
    "rotation": 360,
    "shortestFlag": false
  },
  "platform": "win32",
  "version": "3.33.1"
}

[mifi]

I’m thinking that either one of:

1. there is a bug in ffmpeg that it fails to cut your file
2. if you cut the end of the file, maybe there is not much data at the end (running text) so you don’t gain much by cutting.

could you try to cut a idfferent portion of the file and see if it changes? For example cut the beginning instead of the end.
Also see if it helps if you disable audio and track 1

[NeighbouringPanda]

Okay, I tested 2. and cut where more action is going on, now the file got way smaller.
I didn't know the data-density is inhomogeneous. I better go watch an explanation video about video formats soon... xD

Thanks a lot for quick support,
I think your cool program will come in quite handy for me in future!

[mifi]

Great! Yea I know that modern codecs can compress certain things down very well (like a scrolling text is very simple to store with only a few kilobytes), while other stuff like snowfall or confetti takes a very high bitrate.