Small Import Size Video Leads to Large Export Size / Mbps Question

I have searched high and low on many platforms looking for answer to what I am doing incorrectly.  I make music videos, livestreams and all kinds of things for my music and brand.  I recently did a livestream and the wanted to do some minor edits for a live rebroadcast or "rerun" so to speak with all of the best parts.  The file size has almost quadrupled and I didn't add much except a couple of title screens, and as a matter of fact I actually removed almost 45 minutes of total video.

I know that MP4 and h.264 are the way to go, however what I'm not understanding is how the data rate can be affected so much, and what i need to do to keep it the same or reduce it even.

I see videos in HD all of the time that in MP4 format are 1/10th the size of videos I produce in FCPX.

The last example I gave was a 4GB (3 Hour Livestream) downloaded from YouTube, edited down in time with minimal additions and when I exported it using h.264 at 1080p in M4V for Apple Devices it came out to 14GB!  I would have been 25GB in MP4 for Computers!

The two videos are identical except for size mentioned 4GB vs. 14GB and the data rate... 2.67 Mbps vs. 10.10 Mbps

Can someone shed some light here for me please? I'm an intermediate user and can understand most anything, but the how to get to smaller file sizes for an HD 1080p video eludes me.

Most everything I record is in 24FPS
FCPX 10.5.3
Macbook Pro Mid 2014
Catalina 10.15.17

Basically the higher the data rate the bigger the final file. So to reduce file size you reduce the data rate.
Same with resolution: the higher the resolution the bigger the final file.
So it's a game between reducing resolution and data rate as much as possible while still getting visually good results.
That's it in a nutshell.

MusicByChance wrote: ...I recently did a livestream and the wanted to do some minor edits for a live rebroadcast or "rerun" so to speak with all of the best parts. The file size has almost quadrupled and I didn't add much except a couple of title screens, and as a matter of fact I actually removed almost 45 minutes of total video....I know that MP4 and h.264 are the way to go, however what I'm not understanding is how the data rate can be affected so much, and what i need to do to keep it the same or reduce it even....I see videos in HD all of the time that in MP4 format are 1/10th the size of videos I produce in FCPX...

This is because live-stream captures are typically very compressed -- at the cost of image quality. It's not uncommon to see only 2 megabits/sec or less encoding rate. They also use other encoding tricks such as a big "GOP size" which increases compression but can lower playback quality, esp. on certain scene types.

FCP by itself only exports certain bit rates which are optimized for quality. There is a "web export" preset which you could try, but it still uses a fairly high bit rate.

The best solution is just use Apple Compressor, which allows custom-tailoring all the export parameters, including bit rate. You can create an export preset, import that to FCP, then afterward use it from FCP.

Compressor is only $49, but Handbrake is free. You can also export a ProRes file, import to Handbrake, then re-encode it to whatever compression or bit rate you want.

You can try exporting to 8-bit HEVC from a 720p timeline, but I think that requires importing the built-in preset from Compressor. I think that is due to software licensing issues by the patent holders of the HEVC codec. Procedure: larryjordan.com/articles/configure-final...o-output-hevc-h-265/

You can export HEVC from FCP. Select Apple Devices and choose HEVC 8 or 10-bit. After export the extension can be changed to .mp4.

Thank you everyone! I've been looking at Compressor and wasn't sure it handled bit rate as well, but I already have Handbrake so I'll check that out. I bought another compressor online and converted the file and it stayed the same size so I got frustrated with it and haven't looked again.

These are are helpful suggestions, so I'll try Compressor, and I'll also try the HEVC 8 or 10 and then extension switch as well. Probably some trial and error, but once I get it, then the preset option mention will be helpful. Thanks for the responses.

Thank you for the response... I have experienced the same issue across all file formats, but I should know better with the livestream issue.  The dropped frame rates alone should've keyed me off to the lower bit rate, I just didn't think FCXP would be able to fix and or recreate the compressed version to make it 4X larger.  The quality I'm getting is fine.  It's super clear with the cameras I'm using, so space is truly my only issue at the point.  I'm not making award winning films here... LOL

Again, thanks for the suggestion on Compressor.  Just going to buy it and start reading up on all of it.

Should I stop using 1920x1080?  720 is still a HD quality video.  It will still still fill a screen in 16x9, so that would certainly keep things lower as well.  I just tried the HEVC 8Bit suggestion and the same video as mentioned before in 1080 drops to 10GB and at 720 goes to 7GB.  Most of what I'm doing is going to YouTube anyway, so does it really matter when someone is watching on a phone or tablet?

I tend to think quality in image is a must so I always select 1920x1080 with H.264... maybe adjust the bit rate like you suggested would be the answer?

Thanks again for your time.  This is my first post.

UPDATE:
Compressor is the real deal. I have no idea why I waited to get this but I now understand. In reference to the above topic so there is resolution in case anyone else is reading, I was able to match the bit rate to the original output file after editing, and I also did a mid point between the largest file output size and the original file size Mbps to compare quality.

Original File Before Edit 24FPS 1920x1080 2.5 Mbps 3 Hours = 3.5GB

Compressor Settings with Edits in FCPX
24FPS 1920x1080 2.5 Mbps 3 Hours = 4GB
24FPS 1920x1080 6 Mbps 3 Hours = 8BG
24FPS 1920x1080 10 Mbps 3 Hours = 14GB

I honestly can't see much difference at all between the 2.5Mbps and 10Mbps on my retina screen. Slightly better smoothing/motion and just a slightly crisper picture, however I had to take screenshots to compare just to notice. Having them pulled individually in Quicktime as a reference and watching back to back, I couldn't see it.

Thank you everyone for your help!