Does a youtube video with a still image (ex. music) drain as much mobile data as a moving video (gameplay, etc.), and why/why not?
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I have an actual answer and the answer is *sort of*. The reason is keyframes. Every several seconds in a video, the current image gets sent in its entirety (without motion compression). This is so that if you jump to some time in the video, the player only has to work backwards to the last keyframe, to see what is displayed at that time.
This means the same image gets sent over and over. It can still be smaller than a real video, because there is no data to send about the in-between frames.
Don’t forget if you don’t care about the image you can set it to the lowest quality (usually 240p)
If you do background playback it just downloads the audio and not video, reducing bandwidth considerably.
YouTube Vanced is awesome.
Otherwise video compression works by altering a static image. If the image remains static there’s basically nothing no do, as long as it doesn’t create needless key frames (whole images).
I don’t see an ELI5 answer. So here’s mine:
You only get sent what’s changed for each frame of the video. So if the video doesn’t change in each frame, nothing gets sent except a tiny bit of timing information.
Not an answer, but I’ve also wondered if having your volume all the way up uses more battery
Good answers here, but does anyone have actual data for example for H.264?
In theory it’s slightly less. YouTube uses a minimum 4 key frame refresh. So a still image will be at that 4 frame minimum. But it’s not gonna be noticeable. For a still image just manually set the video to the lowest possible resolution. If I’m listening to something on YouTube I just set it to 140p, lower the screen brightness, out my phone in my pocket and hope it doesn’t Jump around.
So if a video contains a still or mostly still image it *should* be able to compress to a smaller size because it only needs to send the difference between frames (which would be none).
But, sometimes videos are compressed to be a fixed amount of data per second, in which case it would be the same file size no matter what is on screen (so would be basically wasting data).
I’d hope YouTube would use the first option and a video like that would use less data, but there’s no guarantee.
Good answers here, but just as an aside, you can use programs like JDownloader to download youtube videos. You could probably even find some content that has both a static and a moving version and compare the two sizes if you want. You wouldn’t even need to download the videos, as the program will show you the sizes once you input the youtube link.
A YouTube video with less movement is smaller and uses less data. That’s because the video compression (method for reducing size) stores changes from frame to frame. Something like TV static would take the most space, because every pixel changes on every frame. The opposite – a still image, would take the least amount of space.
Imagine you were giving a computer instructions on how to play the video. You can tell each individual pixel what color to be, and repeat that process 30 times every second. But if it is just a still image, you would only have to do that once, and just tell the pixels to stay the color they are for the rest of the video, and that would greatly reduce the list of instructions you would need to send.
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