this post was submitted on 19 Nov 2023
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This may be a stupid question, but I just got back into pirating some shows and movies and realize that many of the QxR files are much smaller than what I downloaded in the past. Is it likely that I am sacrificing a noticeable amount of quality if I replace my files with the smaller QxR ones?

For example, I have Spirited Away from 2017 at 9.83 GB, but I see the QxR is only 6.1 GB. I also have the office from 2019 and the entire show (no bonus content) is about 442 GB, while the QxR version is only 165.7 GB. Dates are what they are dated on my hard drive, can't speak to their actual origin, but they would've been from RARBG. (Edit to add: I also can't really speak to the quality of the downloads, back then I was just grabbing whatever was available at a reasonable size, so I wasn't deliberately seeking out high quality movies and shows - a simple 1080p in the listing was enough for me).

I did some side by side on episodes of the Office (on my PC with headphones, nothing substantial), and I don't notice any differences between the two.

Thoughts on this? Are people better at ripping/compressing/whatever now that they can do so at a smaller size without sacrificing noticeable quality?

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[–] [email protected] 0 points 1 year ago (3 children)

That makes no sense. The bitrate is how many actual bits per second the data uses after compression, so at the same bitrate all codecs would be the same size.

[–] [email protected] 12 points 1 year ago (2 children)

The bitrate is the rate of the video, not the size of the file. Think of different codecs as different types of compression, like rar vs zip vs 7z

[–] [email protected] 12 points 1 year ago* (last edited 1 year ago) (2 children)

I'm not saying it is the size of the file, I'm saying the bitrate multiplied by the number of seconds determines the size in bits of the file. So for a given video duration and a given bitrate, the total size (modulo headers, container format overhead etc) is the same regardless of compression method. Some codecs can achieve better perceived quality for the same number of bits per second. See. e.g. https://veed.netlify.app/learn/bitrate#TOC1 or https://toolstud.io/video/bitrate.php

If it's compressed to 6,000 kilobits per second then ten seconds of video will be 60,000 kilobits or 7 megabytes, regardless if it's compressed with h.264, h.265 or AV1.

[–] [email protected] 1 points 1 year ago (1 children)

Yeah my data is definitely an oversimplification. Raw bitrate doesn’t mean the same between them because they compress differently. I tried to control for that as best I could so it wasn’t the bitrate that was saving file size but the efficiency of the codec.

It’s like a fuzzy start line 🤷‍♂️

[–] [email protected] 4 points 1 year ago* (last edited 1 year ago)

As I've said elsewhere, raw bitrate means exactly the same between them, because the bitrate is the number of bits per second of video after compression. What you mean is that you set a target bitrate and the different codecs have varying success in meeting that target. You can use two-pass encoding to improve the codec's accuracy.

But what matters is the average bitrate required by each codec to achieve the desired level of video quality, as perceived by you. The lower bitrate you need for the quality you want, the better the codec is.

[–] [email protected] 4 points 1 year ago (1 children)

op is describing the source video file bitrate, not the target codec bitrate. 6000kbps compresses to different amounts depending on the codec and quality used. Op doesnt mention the quality factor for the codecs, so this is less than helpful.

[–] [email protected] 1 points 11 months ago (1 children)

You choose the output bitrate by adjusting the quality. If you ask for a 3GB file you get a 3GB file.

[–] [email protected] 1 points 11 months ago (1 children)

Unless you switch to using crf, which tries to give a consistent quality level, damn the file size.

[–] [email protected] 1 points 11 months ago

Of course there are different ways to select the quality level. CRF numbers don't mean anything though, they're just higher or lower than each other.

[–] [email protected] 3 points 1 year ago

You are correct.