H.265 file sizes for TV shows wildy different

[hurtlebum]

Description of problem or question:
I am in the process of ripping my Blu-ray boxsets to a NAS and have noticed that the same Handbrake profile will produce wildly different size output files between different TV shows. Within a given season of a show, they are broadly similar though. As an example, using H.265, Fast, Constant Quality at RF 22 with automatic anamorphic and a 5.1 AC3 soundtrack at 640kbps the first season of Heroes gives files in the c. 1.7-2.1GB range. The excat same profile used to encode The X-Files gives files in the range 0.9-1.1GB, almost half the size.

The source bitrate is about the same for both shows from the blu-ray rip, at around 24MBps however the output files are up to 7MBps for Heros and 3.5MBps for the X-Files. Is this difference in file size simply due to the difference in on screen content between the 2, or have I messed up? X-Files is a much visibly darker programme with quite flat colours, so maybe it compresses better since there isn't as much going on?



Steps to reproduce the problem (If Applicable):
Encoded on 2 different PCs



HandBrake version (e.g., 1.0.0):
1.3.3 (2020061300)



Operating system and version (e.g., Ubuntu 16.04 LTS, macOS 10.13 High Sierra, Windows 10 Creators Update):
Windows 10 Home



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[Lostless]

Handbrake uses a quality Based Veritable bit rate. It will use the least amount of data as possible depending on the quality setting. The amount of compression is based off how much data can be copied from frame to frame. So shows that are static with a lot of still parts, or dark scenes, without a lot of detail, will compress much better vs a fast moving, action packed, quick edited, flashing images.

[Lostless]

Also, the input file size doesn’t matter much as far Compression in handbrake. The end result will probably be very similar if you fed it a lossless, uncompressed Master. Especially blue ray file with their insane video bitrate. Since handbrake is a quality based encoder, if you feed it a highly compressed video, the end result may result in a larger file than the input as it tries to keep the “detail” of the artifacts of a poorly compressed video.