Why does YouTube Export with Filters greatly increase file size

Hi there,

I have a video taken on my iPhone 11 which is 94 mb. I loaded into Shotcut, did some editing cutting bits out, and detached the audio and removed it. I had a wav which was a mix of some audio I recorded separately at the same time as the vid which I then added. The wav file was 48 mb in size, and this also got cut down in the editing to match the vid.

I added a Fade In and Fade Out filter and exported this using YouTube option and the file size created is 50.4 mb. The video goes for 2:21 mins.

I then added the filters:

  • Old Film - Scratches
  • Old Film - Dust
  • Old Film - Grain
  • Saturation

I then exported this with the exact same YouTube setting, and the file size is 638 mb.
How can the file size be so radically bigger? It is like 12 times bigger.

What have I done wrong here?

Original Source Video File Spec:
Length: 3:40
Frame Width: 1280
Frame Height: 720
Data Rate: 3327 kbps
Total Bitrate: 3502 kbps
Frame Rate: 29.97 frames/second

Shotcut Project Video Spec:
Codec: H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10
Resolution: 720x1280
Frame Rate: 29.974125
Format: yuv420p
Aspect Ration: 9:16

Shotcut Export Setting:
From: Timeline
Use hardware encoder = False
Format mp4
Resolution: 720x1280
Aspect Ration: 9:16
Frame/Sec: 29.974125
Scan mode: Progressive
Field order: none
Deinterlacer: YADIF - temporal + spatial (best)
Interpolation: Bilinear (good)
Use preview scaling = False
Parallel Processing = False

Thanks for your time.



Don’t use the YouTube preset. Use the default preset instead. The reason why it produces such big files is to do with the GOP parameter explained here:

That is a LOT of video information added uniquely to each frame of your video.
Video size is a function of many things, one of which is the amount of difference between successive frames. These filters have added significant differences between each sequential frame. In order to maintain the Quality specified, the codec software must increase the percentage of I-Frames, correspondingly reducing the number of small, efficient P-Frames and B-Frames

@Elusien has explained this in another thread…

…which it would do well to read in its entirety.

I do not reproduce this with this specific filters. But I also do not have your exact same media files. I would ask you to carefully perform this test again. But this time, be very careful to only change adding/removing the filters. Be sure to choose exactly the same export preset with making any advanced changes.

If you can reliably reproduce the problem, then try to remove only one filter at a time until you find the one that causes the most change.

Thanks to all that responded. It’s great to see such an active forum for this great product.
So I did the tests as suggested, and here are the results:
(Note Saturation was set to zero which is why it reduced the size a bit I guess)
(Also the only change I made for each test was to add filters, they were all done with the YouTube preset)
50.4 MB: FadeIn, FadeOut
45.3 MB: FadeIn, FadeOut, Saturation
46.6 MB: FadeIn, FadeOut, Saturation, OldFilm-Scratches
47.0 MB: FadeIn, FadeOut, Saturation, OldFilm-Scratches, OldFilm-Dust
638 MB: FadeIn, FadeOut, Saturation, OldFilm-Scratches, OldFilm-Dust, OldFilm-Grain

Then I did one more export with only the OldFilm-Grain filter:
674 MB: OldFilm-Grain

I only have two tracks in the timeline. One is an MP4, and the other is the wav. Only the MP4 has filters applied.



This is as expected because grain adds a lot more information that cannot be removed without reducing the quality level to force it out.

1 Like

I lost my bet; I was betting on OldFilm-Dust.

But the principle is the same: lots of tiny bits of information, distributed uniquely across each frame.

Its the same priciple as with JPG-compression or all other lossy compression algorithms: the more fine detail in the photo (or film) the bigger the file size. Adding fine grain noise is the worst you can probably do with respect to file size. Just be careful with those filters that add a lot of detail - at least be aware of what you are doing :wink: For a comparison: look at a photo with just a blue sky (or anything else with no detail). Then take a photo of grass, bushes with lots of fine detail. At the same jpg-compression rate you will have much bigger file sizes.

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