Video frame rate, resolution, bit rate
Frames per second
When “Let’s make a video”, the video format is:
-Video format (container) = MP4 (.mp4) -Video format
video compression (video codec) = H.264
-Audio compression format (audio codec) = AAC
It is an option. (The video format is summarized here). Later
, what needs to be configured after that is:
・ Frame rate
・ Resolution
・ Bit rate
. Here I would like to summarize this setup.
Table of Contents
1. 1. frames per second
2. 2. Resolution (angle of view)
3. 3. bit rate
4. Profile, level
1. 1. frames per second
Frame rate is an important setting factor that affects the “smoothness” and file size of videos. The unit is fps (frames / second). You can also tell how many still image frames are embedded per second.
A moving image uses the image persistence phenomenon of the human eye to display still images continuously so that they can be recognized as a moving image. It is said that the ability of the human eye can recognize up to 60 fps. So if you create a video at 60fps, you can tell that the video doesn’t look jerky.
On the other hand, this frame rate has a great effect on file size. Since it is necessary to save 60 still images in 1 second at 60 fps and 1 still image in 1 second at 1 fps, the file size varies greatly depending on the frame rate.
Generally, TVs and DVDs use 30 fps (29.97 fps) and most of them are set to 30 fps (29.97 fps) or less.
Unless you really need to reduce the file size, try specifying this 30fps (29.97fps).
For reference when setting less than 30 fps (29.97 fps), 24 fps for movies and 15 fps for 1Seg TV. It is said that it can be lowered to 15 fps for videos with little movement, such as a person sitting and talking. If you set it to 10fps or less, it will no longer be a video but a slideshow level, and it will definitely look jerky. The lowest line for video is around 15fps.
On the other hand, for videos with a lot of movement, such as sports and actions, you may feel that 30 fps (29.97 fps) at the TV or DVD level is not enough. The file size will be large and it will be difficult to send and receive on the internet line, but if image quality is prioritized, it is worth setting it to 60fps.
Current playback devices that support 120fps are still rare, but next-gen TV streaming standards, 4K and 8K streams are specified up to 120fps.
2. 2. Resolution (angle of view)
It can also be said that it is the size of the area where the video is displayed. In terms of TV streaming,
1Seg → SD → HD → Full HD → 2K → 4K → 8K Custom
As the resolution increases, the rendering area increases, so the video file size naturally increases accordingly.
Resolution (angle of view) TV broadcast Compatible storage devices
SD (720 px x 480 px) Analog broadcast DVD
HD (1280px x 720px) HDTV broadcast
* mainly in Europe ――――
Full HD (1920px x 1080px) High definition transmission
* Japan, strictly speaking,
High Definition BS: 1920px x 1080px Transmission
digital terrestrial: 1440px x 1080px Blu-ray Disc
(BD)
4K UHD (3840px x 2160px) 4K UHD streaming means Ultra HD.
Streaming started on December 1, 2018 with the Next Generation Streaming Standard. Ultra HD Blu-ray Disc
(UHD BD)
8K UHD (7680px x 4320px) 8K Transmission As with
4K, streaming started on December 1, 2018. Unknown current status
When considering Internet video usage, YouTube’s maximum resolution is Full HD (HD1080). With reference to this, if resolution is prioritized, it should be set to Full HD, and if file size is prioritized, it should be set to SD or less.
aspect ratio
It is the aspect ratio of the resolution (angle of view). 16: 9 is the standard for televisions, and 16: 9 monitors have become mainstream for personal computers, but there are still products with aspect ratios such as 16:10 and 4: 3, iPhone 3: 2, and Andoroid 16. : is not unified like 9.
Therefore, if the prepared video file has a 16: 9 aspect ratio and the aspect ratio of the device to be played is different, it will be played by expanding / contracting, making margins, etc. on the side of the playback device.
When uploaded to YouTube, videos other than 16: 9 are automatically rendered with black frames at the top, bottom, left, and right.
For those who create and prepare videos, it is very kind to prepare a video file with each aspect ratio, but if not
