Export is Making Larger and Larger File Sizes [19.10.20 - Win 10]

Help/How To
1

Greetings,

While I can’t remember the version of Shotcut I’ve been using (I believe it was 18.something.something), I recently updated to the latest version in hopes that it would fix some issues that I noticed. While it didn’t, I noticed that suddenly, my exported files had much larger sizes than they did before.

I record video that are roughly an hour long on 1920x1080 at 60 frames per sec. The videos average about 22 GB in size and were exporting (with my settings) at a size of roughly 30 - 35 GB.

Settings:

Format - mp4 (doesn’t seem to matter because I saved settings as a custom Preset and you have to still manually enter in “mp4” when you save the file despite it storing the format)

– Video –
Resolution - 1920 x 1080
Aspect Ratio - 16:9
Scan mode - Progressive
Use hardware encoder - check
Parallel processing - check

– Codec –
Codec - h264_nvenc
Rate control - Quality-based VBR
Quality - 80%
GOP - 30
B Frames - 2
Codec threads - 0

– Audio –
Channels - 2 (stereo)
Sample rate - 48000 Hz
Codec - aac
Rate control - Constant Bitrate
Bitrate - 384k b/s

The first exported video I did with the new Shotcut had a size of 38 GB. I saw this and lowered quality from 85% to 80% for the next video and that video’s size was 42 GB.

Lowered the Quality to 75%, next video was 47 GB.

Went back up to 80%, video was 50 some GB.

The video I just exported, same settings as those listed above, 60.4 GB.

Now, some might all my quality settings into question but given I was fine with the output size for quite some time, and without changing quality or video length the file size has been steadily increasing, it’s unlikely that they’re the problem.

Thank you for reading.

2

Since you are using Nvidia hardware encoding this is up to your card and its drivers, not Shotcut. Most hardware encoding does not fully support a quality % higher than something like 70 (just guessing, requires experimentation and depends on GPU abs driver).

3

It’s just strange that these settings were fine for sometime but updating Shotcut has changed that and I am still having that problem. 80% dropped down to 38 GB for a video again and then built up to 53 GB just now for a video that was the same size. I’d think that the GTX 1080 Ti with updated drivers would support this and it seemed to be before now. Anyway, I appreciate you taking the time to answer. I’ll just have to keep testing it out each time it seems.

4

When using quality based VBR at a fixed quality setting, the file size will depend upon the complexity of the video, specifically the amount of fine detail and the predictability of motion between frames.

You can easily get the 25% swings your experiencing.

5

Ah, I see. Thank you. That makes sense. Maybe in some videos I do more fighting or something.

6

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