Compression Question

[R6RR]

Hi,

Not sure this is the right place to ask but trying anyway - i'm trying to conduct some experiment of shooting using my cellphone (Samsung s10e) a 10min video of a wheel first with no movement at all, then another 10min video with same posture and conditions just with the same wheel turning - i'm using a FHD 1920x1080 60fps + h.265 feature setting and im expecting to get different results in terms of the generated files sizes, and for some reason they are the same ~1.09GB...shouldnt i expect bigger size on the moving video? what am i missing?

[manono]

shouldnt i expect bigger size on the moving video?

Not if the phone uses constant bitrate. You can check in MediaInfo

[R6RR]

can you elaborate a bit? doesnt adding moving objects results in bigger file size generation?doesnt it cause the compression engine to send more data because more is changing in each frame? if i have a street camera transmitting its data to a cloud, if the street is empty vs packed with moving cars wont i get a bigger file for the latter?

Thanks!

[manono]

I don't know for sure how it was encoded. I was just providing one scenario where they could both wind up the same size. They could even have ABR or VBR encoding if the average bitrates were the same. Those would wind up the same size also. Have you checked the 2 versions in MediaInfo?

doesnt adding moving objects results in bigger file size generation?

Not necessarily. If the bitrate for both is the same, the resulting filesizes will be the same. Filesize is entirely dependent on the video length and the average bitrate used. Now, if it was quality-based encoding then, yes, there might be large differences in the resulting file sizes.

[R6RR]

[Attachment 54728 - Click to enlarge]

what should i look in MediaInfo that will explain this?

[jagabo]

can you elaborate a bit? doesnt adding moving objects results in bigger file size generation?doesnt it cause the compression engine to send more data because more is changing in each frame?

When you are using constant bitrate encoding your are explicitly telling the encoder to use the same bitrate for any video. All videos of the same duration will result in the same file size because

size = bitrate * time

[johnmeyer]

There is only one thing which determines file size: bitrate.

Frames per second (fps) doesn't matter. 24 fps and 60 fps will produce the same files size if you encode them both at the same bitrate.

Resolution doesn't matter. SD, HD, and 4K will all produce the exact same file size if encoded at the same bitrate.

Video content doesn't matter. A static shot of a building, taken from a tripod will produce the same file size as hand-held footage of a stock car race.

People get confused because some software uses a "constant quality" encoder where the encoder does indeed look at the content of the video, and where there is lots of motion, it will increase the bitrate, thus producing a larger file size. However, I'm not sure any video camera has such an encoder because to work correctly, it has to be able to look at multiple frames to know how much motion is going on. This takes a huge amount of memory, CPU power, and time, and would be exceedingly difficult to do in real time inside a video camera or cell phone.