this post was submitted on 19 Nov 2023
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Same movie. 1080p. 2h. 6000 Bitrate. AAC 5.1 audio.
You can't just compare the file sizes without looking at the quality. Each will have different quality loss depending on the exact encodings used.
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.
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
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.
Well, we're talking about fully compressed videos in this thread.
Yes, we are. And my point stands. The bitrate is the number of bits per second of video, as measured on the fully compressed video.
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 🤷♂️
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.
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.
You choose the output bitrate by adjusting the quality. If you ask for a 3GB file you get a 3GB file.
Unless you switch to using crf, which tries to give a consistent quality level, damn the file size.
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.
You are correct.