Video frame rate, resolution, bit rate Part 2
Interlaced and progressive
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It can be expressed by adding iop to the end of the resolution, such as 1920 x 1080i and 1920 x 1080p.
This is a screen display method called
i: interlaced method
p: progressive method
. For example, if the 8.00 Mbps bit rate screen described below is displayed for only 1 second, the interlaced method displays the screen. The numbers of 1px horizontal lines called scan lines are alternately displayed within 0.5 seconds, the progressive method displays all scan lines as they are for 1 second.
The interlaced method is said to look smooth when the image has a lot of movement and is used primarily on televisions. On the other hand, the progressive method is said to be clearly visible in the case of images with little movement, and it is not mainly used in personal computers, but the interlaced method cannot be compatible with personal computers.
Each has advantages and disadvantages, but it is a level of difference in method and does not fundamentally affect the level of image quality, such as frame rate and bit rate.
3. 3. bit rate
Set the amount of video information that is retained per second. For the bit rate, set the video and audio separately.
Video Bitrate
Regarding the bitrate of the video, the higher the bitrate, the more information the video will have, so the video will be clearer, and the lower the bitrate, the blurrier the video will be.
The higher the bitrate, the better the image, but for example, it is useless to increase the bitrate even if the resolution is low, the playback load will increase, and the file size will increase unnecessarily … In other words, it is important to set a suitable bit rate according to the frame rate and resolution. The guideline is as shown in the following figure.
-Video Bit Rate Settings Guide (Minimum) –
Resolution (image quality) / frame rate Frame rate 29.97 fps or less Frame rate 30 fps or more
1Seg (360px x 180px / 240px) 0.75 Mbps ~ 1.00 Mbps ~
SD (720 px x 480 px) 2.50 Mbps ~ 4.00 Mbps ~
HD (1280px x 720px) 5.00 Mbps ~ 7.50 Mbps ~
Full HD (1920px x 1080px) 8.00 Mbps ~ 12.00 Mbps ~
2K (2560 px x 1440 px) 16.00 Mbps ~ 24.00 Mbps ~
4K (3840px x 2160px) 45.00 Mbps ~ 68.00 Mbps ~
8K (7680px x 4320px) 130.00 Mbps ~ 200.00 Mbps ~
Audio bit rate
The guideline for the audio bit rate is shown in the following figure. The size is very small compared to the video.
-Guide to configure the audio bit rate-
Voice type bit rate
monaural 128 Kbps
stereo 384 Kbps
5.1 Surround Sound (Dolby Digital) 512 Kbps
Bit rate control method
As a method of controlling a bit rate,
CBR (for Constant Bit Rate: Constant Bit Rate)
VBR (Variable Bit Rate: Variable Bit Rate)
ABR: (Average Bitrate Average Bitrate)
has three methods.
Generally, for stability during playback, use CBR where the bit rate does not change in the scene.
4. Profile, level
Profile and Level are names that combine the frame rate, resolution, and bit rate values explained so far for each purpose. So to speak, it can be called the name of the video setup menu.
Every device (iPod, iPad, iPhone, PSP, Switch, Android, etc.) publishes recommended profiles and levels, which will naturally allow you to set the optimal frame rate, resolution and bit rate …
Select the target device with the video editing software, but at this point, select the profile and level internally.
By the way, this profile and level are strictly the H.264 video compression format (video codec) setting standard. See here the video compression format.
-Profile, level list (simplified version) –
Level / Profile Baseline
profile of
Main baseline
profile
main High
profile
high
Level 1.3 Frame rate: 30 fps
Resolution: 352px x 288px
Bit rate: 0.75 Mbps Frame rate: 30 fps
Resolution: 352px x 288px
Bit rate: 0.96 Mbps
Level 2.2 Frame rate: 30 fps
Resolution: 352px x 480px
Bit rate: 10 Mbps Frame rate: 30 fps
Resolution: 352px x 480px
Bit rate: 20.0Mbps
Level 3.2 Frame rate: 60 fps
Resolution: 1280px x 720px
Bit rate: 10 Mbps Frame rate: 60 fps
Resolution: 1280px x 720px
Bit rate: 25.0Mbps
Level 4.2 Frame rate: 60 fps
Resolution: 2048px x 1080px
Bit rate: 50Mbps Frame rate: 60 fps
Resolution: 2048px x 1080px
Bit rate: 62.5 Mbps
