do tvs have frame rates Archives

Sampling frequency and depth of bits

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Sampling frequency and depth of bits

Frame rate per second

What is the sampling frequency?

Frame Rate

What are the depth and speed of bits?
The sound quality is determined by the sampling frequency and the depth of bits.

When I read the history of sampling frequency and bits frequency on the network, I flood incorrect information.
Some people think subjectively about what frequency is better. There is a definition and a physics suitable for the frequency (sampling frequency) and the bit rate.
It is not something you can guess what is better (laughs)
, so why not study the sound quality mechanism and replace it for the quality of the video?

What is the sampling frequency?
There is something similar to the speed of frames in the world of sound.
That is the sampling frequency.
The sampling frequency is an index that indicates how many times a sound is converted per second when converting an analog signal into a digital signal.
In terms of video, 24 fps has 24 photos aligned in a video of 1 second.
In terms of voice, 44,100Hz means 44,100 digital sound samples are aligned in a second sound.
The unit is Hz.

Reference source: https://pixabay.com/en/equalizer-eq-sound-level-digital-255396/

By the way, the conversion is called AD conversion (analog to digital conversion abbreviation).
I think this meaning is difficult to understand and the information is complicated.

It is said to be standard only after converting the analog signal to digital 44,100 times per second, so the human ear is strange! That’s why.

By the way, the “sampling frequency” is the “frequency of frames” in the video.
To deepen the understanding of the sampling frequency, I will replace it with a video and continue with the story.

The frame rate of a video is called FPS (frames per second) and is expressed using the unit of how many photos are displayed per second.
And the video is more fluid at 30 fps and 60 fps than at 24 fps.

In other words, the greater the sampling frequency, the softer the sound will be.
The sound is the same and 48,000 Hz is softer than 44,100 Hz.

Before talking about what sound he prefers, first understand what sound the highest sound quality has by definition.
This is important.
By the way, it is important to understand the difference between 44,100Hz and 48,000Hz by making images.

VOOK article link “The difference between 44,100 Hz (music industry) and 48,000 Hz (video industry) that you get to know”

Did you know the sampling frequency?

What are the depth and speed of bits?
Remember only two more terms.
That is “depth of bits” and “bit speed”.
Be careful because names are similar but not equal.

These three words are simply expressed like that.

Sampling frequency (Hz) x Bit depth (bit) x Number of channels = BITS speed (BPS)

The best-known CD bit rate is 44,100 Hz x 16 bits x 2 channels (stereo sound) = 1411200 bits = 1411.2 Kbps

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What is a frame rate? Part 2

FPS

Video coding and bit rate

fps

The coding method is also related to the image quality of the video.

When compressed a video, the image quality of the video is determined by the amount of data processed per second, which is called a bit rate.
The same happens with the voice.
This includes both video and audio, so the video bit rate is the sum of the video bit rate and the Audio Bit Rate.
If you configure both at a high bit rate, you will get a beautiful video and video audio, but the size of the video will be great.
In addition, since the bit rate is fixed in a general compression method, if the frame rate increases at the same bit rate, the number of bits in the frame will be reduced accordingly and the quality of the image will deteriorate.

There is also a method called a variable bit rate, in which the bit rate increases when the movement is large and the bit rate decreases when the movement is small, but this requires a large amount of CPU processing for compression / decompression .
In any case, if you do not have enough bandwidth to send and receive, you must maintain the video bit rate at a certain level, and if you do something better, something will go wrong.

Video of the next web conference
First, starting in 2019, the bandwidth of the network is up to 2 Gbps even for domestic lines and optical lines.
Video compression methods are also evolving. For example, as of 2019, H.264, which is a general video compression method, it has double compression speed that MPEG-2, which is a conventional compression method for DVD, etc. That the compression rate will double in H.265, which will be formulated below.
In other words, it can be said that the environment to send and receive videos created at a higher bit rate is much better than the videos used in conventional web conferences.

In the future, it is expected that new systems and improved systems allow higher quality web conferences for both video and audio.
In addition, it will increase the number of people who can participate and the screen, and it will be possible to make a fairly large web conference.

What is a frame rate?

FPS

The rate of frames is the amount of frames that processes a video at a certain period of time (usually 1 second) and is related to the image quality of the video.

fps

This article describes the speed of frames.

Table of Contents

1 speed of frames, video and frames
2 Frame and web conference speed
3 Video coding and bit rate
4 Video of the next web conference
Frame speed, video and frames
Have you ever wrote an animated book on the edge of a notebook when you were a child?
It is a sleeve that seems to be moving when you change the image little by little and pass the pages.
Actually, the beginning of the video image is the same as that of this animated book.
It is said that the film was thrown into the public as a cinematographic film invented by the Lumiere brothers.
The principle was to record 16 images per second in film, print them and reproduce them to record and reproduce the images.
At first, it was a video called silent without audio, but eventually it became a video called Talkie with audio.

At this time, 24 images per second are required to record audio, and the concept of frame speed is born for the first time.
The frame rate is the number of frames (still images) that can be processed per second, and Normally FPS (frames per second) is used, which is the number of frames that can be processed per second.
Since the talkie requires 24 frames per second, the frame rate is 24 fps. The higher the speed of frames, the softer the movement will be, since more frames can be used to reproduce the same movement.

However, increasing the frame rate increases the number of frames processed per second, which results in a large number of film.
Therefore, 24 fps has become the standard for movies.
The next is the birth of television.
There are standards for televisions called PAL and NTSC, but the frame rate is 25 fps for PAL and 29.97 FPS for NTSC.
And in the latest 3D games, etc., the frame rate has increased to 60 fps.
As the content that requires a high speed of frames, such as 4K televisions and 3D movies, it will continue to increase, 120 fps videos are expected to appear.

Frame rate and web conferences
At 15 fps, it is not unnatural if you can only see the upper part of the person who attends the conference, as a web conference, and the movement is not so violent. In addition, in web conferences, audio is more important than video.
In a meeting, the video can be an extreme still image, but the meeting can not be done unless the audio is clearly transmitted.
In addition, since it is necessary to send video and audio in real time, the video frame rate tends to be as low as possible.

It seems that many general web conference systems send videos at 15 fps.
However, some modern systems also admit HD image quality at 30-60 FPS.
Of course, you need a line that can send and receive that amount of data, but you can expect more clear and clear images than conventional web conferences.