Video Format Conversion Bitrate Question
If the original video bitrate is 2Mbps, then I set the output bitrate to 2Mbps, will the image quality be reduced?
A video, the number of images it consists of every second, is called the frame rate of the video. Common frame rates are 24000/1001=23.976, 30000/1001=29.970, 60000/1001=59.940, 25,000, 50,000, etc. This number is the number of images flashed in one second. For example, 23,976 means 24,000 images in 1001 seconds. The frame rate of the video can be constant (cfr, Const Frame-Rate) or variable (vfr, Variable Frame-Rate)
The definition of bitrate is the volume of the video file divided by time. The unit is usually Kbps (Kbit/s) or Mbps (Mbit/s). Note that 1B(Byte)=8b(bit). So a 24 minute 900MB video:
Volume: 900 MB = 900 MByte = 7200 Mbit
Time: 24min = 1440s
Bit rate: 7200/1440 = 5000Kbps = 5Mbps
When the length of the video file is basically the same (for example, the current episode is about 24 minutes), bitrate and volume are basically equivalent, and both are parameters used to describe the size of the video. Files with the same length and resolution have different volumes, which are actually different bit rates.
Bitrate can also be interpreted as the total amount of data used to record the video per unit of time. The higher the bitrate of the video, the more data is used to record the video and the possible interpretation is that the video may be of better quality. (Note that it’s only potential. We’ll discuss why high bitrate doesn’t necessarily equal high image quality later.)
3.
Bit depth, which is what we usually call 8 bits and 10 bits, refers to precision. 8 bits means that each channel is represented by an 8 bit integer (0~255), and 10 bits is shown by a 10 bit integer (0~1023). 16 bit is 0 ~ 65535
(Note that the above expression is not rigorous. When the video is encoded, it is not necessarily possible to use the whole range from 0 to 255, but it can be reserved and only a part is used, such as 16 to 235. We will not detail it here )
Your monitor is 8-bit, which means it can display all intensities from 0~255 for each channel of RGB. However, the color depth of the video is the color depth of YUV. When playing, YUV must be converted to RGB by calculation. Therefore, the 10-bit high precision is indirect, which increases the precision during the operation so that the final color is more delicate.
How to understand the 8 bit screen, you need to play 10 bit:
The radius of a circle is 12.33 m, find its area and keep two decimal places.
The precision of the radius is given to two decimal places, and the result also requires two decimal places, so how high should the precision of pi be? Only two decimal places? Taking pi = 3.14, the area is calculated to be 477.37 square meters. Taking pi = 3.1416, the area is calculated to be 477.61 square meters. The precision of pi is high enough, and the area is calculated to be 477.61 square meters. So taking pi=3.1416 is enough, but 3.14 is not enough.
In other words, even if the precision of the final result is lower, it does not mean that the numbers involved in the operation and the operation process can maintain a lower precision. Based on the premise that the final output is 8-bit RGB, this is why 10-bit YUV still has the precision advantage over 8-bit YUV. In fact, after 8-bit YUV conversion, the coverage accuracy is about 26% of 8-bit RGB, and the accuracy after 10-bit conversion can cover about 97%. Do you want your 8-bit screen to display 97% accuracy? Look at 10 bit.
8-bit precision is not enough, mainly in the low-brightness area, and it is easy to form color banding.
