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What is the code rate? Part 3

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What is the code rate? Part 3

code rate

Video imaging methods are mainly divided into two types: interlaced scan and progressive scan.

code rate

In plain and simple terms, an image (a frame) is made up of lines made up of hundreds of rows of pixels.

Interlacing means that only half of the lines are displayed on one screen at a time, and is made up of odd or even lines, displayed alternately with each other. It is commonly said “i”.

Originally, the image the TV would transmit per second was set to 50 frames per second. Think that the image does not flash in our eyes. However, according to the technology at the time, it was difficult to achieve 50 frames per second of TV transmission. Scientists used the persistence of human vision to invent interlaced transmission.

Interleaving is a technology developed to transmit television signals using limited bandwidth. In an interlaced system, only half the number of horizontal lines per video frame is transmitted at a time. The viewer can perceive each frame at full resolution due to transfer speed, display persistence, and persistence of vision. All analog TV standards use interlace technology. Digital television standards include interlaced and non-interlaced technologies.

(The above is official Adobe content)

We all use no field (line by line) now

video ratio

Video ratio refers to the ratio of the length to width of the video screen played by the video player. The ratio between the length and width of the CRT television used in ordinary homes is 4:3, that is, the video ratio is 4:3. The high-definition screen video ratio (TV and mobile) that is currently being developed is 16:9. The current full screen mobile phone is 17: 9

Due to the development and application of various screens, video production is also relatively informal, and will be adjusted according to the requirements of Part A, such as large conference screens and advertising screens.

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What is the code rate? Part 2

Code Rate

Generally speaking, there are only a few common frame numbers that we use to make videos: 24 frames, 25 frames, 29.97 frames, and 30 frames.

code rate

Different areas and different uses require different frames.

Frames per second

Frame rate is also known as the abbreviation FPS (Frames PerSecond): frames per second. It refers to the number of image frames that are updated per second, which can also be understood as the graphics processor can update multiple times per second. The more frames per second (FPS), the smoother the motion is displayed. When capturing dynamic video content, the higher the number, the better.

If the frame rate exceeds the refresh rate of the screen, it only wastes graphics processing power, because the monitor cannot refresh as fast, so the frame rate that exceeds the refresh rate is wasted.

For games, in general, first person shooters pay more attention to the FPS level, if FPS is <30, the game will seem inconsistent. So, there is an interesting saying: “FPS (referring to FPS games) focuses on FPS (referring to frame rate).

The frame rate is not as high as possible. Most common mobile phone recording frame rates on the market are 30fps, TV 25/30 (common use) 50/60fps, etc. (sports shots), high-speed cameras 120/240 fps (slow motion)

iphone7 camera parameters

Resolution

Resolution, also known as resolution and resolution, can be classified into two directions: screen resolution and image resolution.

Screen resolution (screen resolution) is the accuracy of the screen image and refers to how many pixels a monitor can display.

What is the code rate?

What is the bit rate for? What is frame rate? What is the resolution?

Students often ask, what is the code rate? What is the bit rate for? What is frame rate? What is the resolution?

This problem of not being able to speak clearly, listening and not understanding has worried many beginners.

Today Ben Shuai specially came to solve these professional terms for you.

frame

In the video, do you know what the unit less than a second is?

That’s right, it’s what I’m going to talk about today: “framework”!

Frame: It is the smallest unit in video animation and countless frames constitute seconds.

Simply put, one frame equals one image, and a second is made up of a certain frame, that is, a certain number of images!

Play the images continuously and you will see dynamic images under the influence of the visual residue produced by your eyes.

The more frames per second, the smoother and more realistic the images we see!

We also call the number of frames in 1 second the number of frames, usually expressed in fps (FramesPer Second).

What does MP3 bitrate mean?

Bit rate

The rate at which a digital channel transmits digital signals is called the data transfer rate or bit rate.
The word bitrate has many translations, such as bitrate, etc., which indicates how many bits per second the encoded (compressed) audio data should be represented, and a bit is the smallest binary unit, either 0 or 0. 1. The relationship between bitrate and audio and video compression is simply that the higher the bitrate, the better the quality of the audio and video, but the larger the encoded file; if the bitrate is lower, the situation is reversed.

For example: encode audio and video at 500 Kbps.
where bps are bits 1K = 1010 = 1024
b is little
s is the second
p is for (for)
Therefore, encoding at 500 kbps means that the encoded audio and video data must be represented at 500 K bits per second.
In the baseband transmission system, the bit rate is used to represent the code rate of transmitted information.
The bit rate Rb refers to the unit of time
The number of binary bits transmitted within the unit, the unit is b/s. For example, the transmission speed of a computer serial port is up to 115200b/s.
The symbol rate or baud rate Rs refers to the number of modulation symbols transmitted per unit of time, that is, ternary and ternary
The information transmission rate of the multivariate digital code stream in the

In M-ary modulation, the relationship between the bit rate Rb and the baud rate Rs is:
Rb=Rslog2M
The sampling rate refers to the ratio of the sampling samples to the total number of samples, and the sampling rate refers to the number of samples per unit of time. If it is an instrument, the sampling rate is 40MSa/s, which indicates that the number of samples per second is 40M, but it cannot be represented by 40MHz.

The process of converting analog audio to digital audio is called sampling. In a nutshell, how much data is needed to record a 1 second duration of sound via waveform sampling. A sound with a sample rate of 44 KHz requires 44,000 data points to describe a 1-second sound waveform. In principle, the higher the sample rate, the better the sound quality.

What is bit rate? Knowledge of the MP3 audio format. Part 2

Bitrate is a benchmark indicator of the efficiency of digital music compression.

The bit rate represents the number of bits bps (bit per second, bits per second) transmitted per unit of time (1 second). We usually use kbps (in simple terms, it is per second) clock 1000 bits) as the unit. The bit rate of digital music on CD is 1411.2 kbps (ie recording 1 second of CD music requires 1411.2 × 1024 bits of data). The higher the bit rate of the music file, the more data (Bit) must be processed in a unit of time (1 second), and the better the sound quality of the music file. However, when the bit rate is high, the file size increases, which will occupy a large amount of storage capacity. 8 to 320 kbps.

1. WMA (Windows Media Audio, Windows Media Audio)

As a Microsoft media compression method, it is a part of the technology that compresses only audio data in Windows Media Technologies. The sound quality is similar to MP3 and can be compressed with half the technology of MP3. It has the copyrighted Windows Media Rights Manager, which can be played by installing in WMP (Windows Media Player, Windows Media Player). Due to the strong influence of Microsoft and Windows, as well as major copyright reasons, the major American record companies EMI and BMG have officially confirmed that they use the WMA method developed and produced by Microsoft. It is believed that this advanced method will become even more popular in the future.

2. MP3 (CBR, VBR, ABR)

MP3 is currently the most widely used and widely used lossy compressed digital audio format, which has been explained above and will not be repeated here.

CBR (constant bit rate)

CBR is the oldest and simplest MP3 encoding (compression) method. When this method is used for encoding, the bit rate of the entire file is the same, in other words, the bit rate used by the MP3 file per second is the same. Although the music file has sections of varying complexity, the encoder always keeps the bit rate constant, unless you use the highest sound quality, otherwise the sound quality of the different sections of the MP3 file will vary. The more complex the passage, the worse the sound quality. Its biggest advantage is that the file size is fixed, which is convenient for calculating storage space.

What is bit rate? Knowledge of the MP3 audio format.

Digital audio formats are audio signals that are recorded, processed, and reproduced in digital form.

The emergence of digital audio formats is to meet the needs of high-fidelity playback, storage and transmission. Simply put, early analog audio formats had issues with playback distortion and glitches due to media wear. Since the advent of CD discs, audio files in digital format have become popular, but another problem has arisen: the limitation of storage volume and the phenomenon of CD disc wear is still present. Saving to a hard drive (in connection with longer storage time) is also not a good solution when storage media (mainly hard drives) are still expensive at the time. The rise of the Internet has created a requirement for long-distance file transmission. Under the restriction of bandwidth, the demand to reduce file size has become more intense. All this has led to the generation of lossy compressed digital audio formats from external factors!

In terms of internal factors, with the improvement of computing and coding capabilities, the progress of various acoustic psychological models has promoted the emergence of various lossy compressed digital audio formats. Some of the most commonly used audio formats in MP3 players are briefly introduced below: MP3 (CBR, VBR, ABR), WMA, WAV, ADPCM, and the emerging audio formats AAC, ASF, and OGG.

Before introducing various digital audio formats, let’s clarify one concept: bitrate.

In the field of computing, all information is digitized. Bit is the smallest unit of data in a computer, it refers to a number of 0 or 1, which is a mathematical binary number, a “0” or “1” , is a bit. For example, when we say a 2-digit number, it means that it is a two-digit binary number, and there are 4 combinations of “00”, “01”, “10” and “11”, which represent 0, “11” in decimal respectively. 1, 2 and 3 are four numbers.