I suspect that action cam footage may be using a non-standard codec, more like an H.265 rather than an H.264. But in any event, start with the specs of your original file.

Open your action cam footage in the free download MediaInfo. In MediaInfo, set View to Text and then coopy the text from this complete report and paste it to this forum.

We'll better be able to advise you once we see the file's complete specs.

Thanks meanwhile for the mediainfo step hint.

here is the result.

Generale
Complete name : C:\temp\DJI_0053_018.MP4
Format : MPEG-4
Format profile : JVT
Codec ID : avc1 (avc1/isom)
File size : 3,81 GiB
Duration : 6 min 48s
Overall bit rate mode : Variabile
Overall bit rate : 80,1 Mb/s
Encoded date : UTC 2020-10-25 12:08:05
Tagged date : UTC 2020-10-25 12:08:05
Comment : DE=None, Type=Normal, HQ=Normal, RS=On, Mode=P
Video
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format profile : High@L5
Format settings : CABAC / 1 Ref Frames
Format settings, CABAC : Si
Format settings, Reference frames : 1 frame
Format settings, GOP : M=1, N=30
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Duration : 6 min 48s
Bit rate mode : Variabile
Bit rate : 80,0 Mb/s
Width : 1.920 pixel
Height : 1.080 pixel
Display aspect ratio : 16:9
Frame rate mode : Costante
Frame rate : 59,940 (60000/1001) FPS
Color space : YUV
Chroma subsampling : 4:2:0
Bit depth : 8 bit
Scan type : Progressivo
Bits/(Pixel*Frame) : 0.644
Stream size : 3,80 GiB (100%)
Title : DJI.AVC
Language : Inglese
Encoded date : UTC 2020-10-25 12:08:05
Tagged date : UTC 2020-10-25 12:08:05
Color range : Limited
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Codec configuration box : avcC
Audio
ID : 2
Format : AAC LC
Format/Info : Advanced Audio Codec Low Complexity
Codec ID : mp4a-40-2
Duration : 6 min 48s
Bit rate mode : Costante
Bit rate : 192 kb/s
Channel(s) : 2 canali
Channel layout : L R
Sampling rate : 48,0 kHz
Frame rate : 46,875 FPS (1024 SPF)
Compression mode : Con perdita
Stream size : 9,23MiB (0%)
Title : DJI.AAC
Language : Inglese
Encoded date : UTC 2020-10-25 12:08:05
Tagged date : UTC 2020-10-25 12:08:05
Altri
Type : meta
Duration : 17 ms
Bit rate mode : Costante
Default : No

The mediainfo shows that the 1080p video has a high bitrate of 80 Mbps. Shadows files will be needed on your i7 pc.

You need to use a 59.94 timeline for editing this footage for best accuracy. Use the Profile Analyzer to create a custom file to produce the edited footage. To save on final produced file size try the default avc 1080/30p 17 Mbps mp4 setting. It should work fine as I use streaming video at 1080/30p at 5 Mbps as long as the footage is in daylight and there is no excessive motion.

Thanks a lot

Indeed I managed to get the video result I wished, optimizing the final size from 22GB to 5Gb, with the 1080/30fps @10Mbps since the video was about continuos motion.

As an additional doubt, I wonder then if if there was a mathematical formula to get the optimum editing settings from the shooting video or it's so personal which gets defined by experience and trials.

I also wonders if I should slow down the shooting from 60 to 30 fps, since I doubt I'd use the slow motion feature so many times to justify the double size.

Thanks anyway, your suggestions helped me finding out the result I was aiming for.

Phil

Quote I also wonders if I should slow down the shooting from 60 to 30 fps, since I doubt I'd use the slow motion feature so many times to justify the double size.

Really probably more of a personal choice than anything. For me, I always record in the best available that the camera has to offer. One can always downscale during produce very easily for various types of display, but it's very difficult to near impossible to upscale effectively. Storage is cheap. What one uploads to share with someone to view on a phone has radically different produce requirements than perhaps displaying on that future large screen TV.

Jeff