HIFI Introduction What is the audio/video bit rate and sampling rate?

Recently I bought the most expensive headset I have ever purchased: Baiya dt131. According to official instructions, this is an entry-level hifi headset. however, when I received the goods and started to try it out, I was a little disappointed: the sound quality was similar to that of the goods sold for dozens of dollars, and the appearance was still ugly. I started to query the relevant information online. After one afternoon and one night, I finally figured it out.

HIFI is short for English high-fidelity. Its literal translation is "High Fidelity". It is defined as a replay sound highly similar to the original sound. Generally speaking, it refers to playing high-quality music through a series of equipment. In specific categories, there are portable hifi, desktop hifi and pchifi which have emerged in recent years.

A typical hifi system usually consists of six parts: power supply, wire, audio source, decoder, power amplifier, and Speaker (passive ). powered by a power supply, data is transmitted by cables, and digital signals on the media are obtained from audio sources. The decoder converts digital signals into analog signals, and the power amplifier scales up analog signals, at last, the speaker (passive) converts the enlarged analog signal to a sonic stream for playback.

For portable hifi, it is impossible to create too much because of portability limitations. in the current development, there are two parts: audio source and speaker. the audio source here is actually a small all-in-one machine, which includes audio sources, decoder and power amplifier, while the speaker generally refers to headphones or ear plugs.

For a standard desktop hifi, the audio source, decoder, power amplifier, and speaker are four independent devices. the audio source is a turntable. The media for storing music is CD/DVD or other types of records. The turntable reads digital signals from the media.

For a set of standard pchifi, compared with desktop hifi, it can be understood that the same is true except for the sound source and media. the audio source here refers to the computer, including the hardware and operating systems of the computer, and the media is files on the hard disk.

Not everyone can afford the price of a set of standard hifi devices. In this case, we need to integrate the above six standard components and scale down the specifications to save costs. the first step is to integrate the power amplifier and the Speaker (passive) into the active speaker. In this case, the speaker of the Power Amplifier device can also emit sound. the second is to integrate the decoder into the sound source, specifically the sound card. since the current device is a computer host + speaker, the power of the audio source is the power of the host. If the speaker is a headset or ear plug, it does not need independent power. the only cable that can be affected is the data connection between the computer host and the Speaker.

After integration, an entry-level pchifi device is no different from an ordinary multimedia computer. It is a host + speaker. the difference is that a sound card (decoder) and a sound speaker (Power Supply + speaker) must be used.

However, this sentence is not appropriate. A multimedia computer is not just a set of pchifi. From the sound card perspective, it has three basic functions: first, the music synthesis and pronunciation function; the second is the mixer and DSP functions. The third is the input and output functions of analog sound signals. Pchifi uses only half of the third function: analog signal output. from a more detailed point of view, the output analog signal is divided into x.0 and X.1, the former is generally 2.0, used to listen to music, which is also the channel used by hifi; the latter is generally 2.1, 5.1, 7.1, etc., used to watch movies.

There is no absolute relationship between a pchifi device and listening to good music. Factors that affect the quality of music mainly include the music media, playing devices, and listener's preferences and mood.

As mentioned above, for pchifi, the media is a file on the hard disk. the formats of music files are divided into two types: lossy compression format and lossless compression format. The specific specifications are sampling rate, sampling bit and bit rate. the specific definition can be Baidu encyclopedia. as the name suggests, only music files with a high sampling rate, sampling bit and Bit Rate in lossless compression format can lay the foundation for better listening performance. generally, ape or FLAC is a lossless format, while the sampling rate of CD music, sampling bit and bit rate are44.1 kHz, 16 bits, 1146.6kbps.

The playing device is a key factor affecting the listening effect. ordinary multimedia computers can also play songs, entry-level pchifi, and standard PC/desktop hifi, but their playback quality is obviously different. how to choose the right equipment and matching methods is a profound and profound problem. It takes countless people to complete the experiment, this is clearly not what I can solve by someone who wants to build an entry-level hifi. I will discuss other issues here.

I. Why are desktop hifi and pchifi of the same level, and even two sets of devices with the same audio source? in most cases, desktop hifi is doing better?

The answer I can find is in general: This is the gap between a general system and a dedicated system. in addition to listening to music or music, desktop hifi can also play games, access the Internet, and write blogs. in terms of design, it is impossible for a PC to be designed based on hifi. it sacrifices the performance of many specialized fields to achieve its versatility.

For more specific reasons, see the reference listed below.Article: For guidance, the principle of pchifi has a very detailed explanation on the 190,242,255,291,293 floor. I will refer to the statement on the 293 floor for the time being:

1st topic: on the basis of no data errors and identical backend devices, is pchifi sound quality inferior to cdhifi? Is it a jitter problem? The discussion results and consensus are as follows: Yes! The theoretical basis is that PC functions are too powerful and complex. Pchifi generates a large number of jitter instances because of the electronic components in the chassis, IBM architecture, system bus, CPU, and many other factors. We all agree that pchifi as a sound source is a jitter problem. As for the current situation, if there are other reasons, it is also a secondary reason. 2nd topic: Can pchifi eliminate its serious jitter problems through technical means to achieve the goal of high sound quality? The discussion results and consensus are as follows: Yes! The theoretical basis is: Although pchifi is a serious problem as a sound source jitter, the back-end efforts can further reduce the impact of jitter. For example, asynchronous USB + cache + independent clock can effectively solve the majority of jitter impact caused by the front end, but the cost will also increase exponentially. Therefore, compared with the desktop CD designed for audio playback, pchifi, as the audio source, has to pay a lot of cost at the backend to achieve sound quality. 3rd theme: if the future of "Digital hifi System" is not in PC, where will it be? The discussion result and consensus are as follows: "A professional desktop streaming media audio player with a PC architecture and a solid storage device is removed ". The theoretical basis is: it removes the IBM architecture, bypasses the complicated PC motherboard circuit, solves the vibration of the CD mechanical turntable, and abandons all functions unrelated to the sound quality, in line with the philosophy of "professional skill", the only purpose of the design is to minimize the impact of jitter on digital audio and pursue the best sound quality. Therefore, "it" is likely to be the future direction of digital hifi.
 

So what is jitter? Let me refer to the 255 floor explanation.

There are so many noises. Let me describe the jitter of audio digital transmission. We think of audio digital transmission as a supply chain, which has a lot of goods (nodes ), each node corresponds to an audio frame data, and the connection between each node is considered as a timing time interval, that is, the time interval between delivery and delivery. DAC male requires digital input and can be considered as a chain receiver, PC + USB male as a chain provider. What do we often say about the 44.1 k Hz audio data? DAC male needs to get 44100 nodes in one second, and the interval between each node must be 1/44100 seconds. if the DAC male cannot get a total of 44100 nodes per second, this is called clock drift, which is the clock offset. This is the worst case if the DAC male gets 44100 nodes per second, but the interval between each node is not 1/44100 seconds, so this interval is called jitter. The problem may be caused by DAC male, PC + USB male, or the path between the two is too narrow. To simplify the problem, we should consider DAC male as the best labor in the universe and work on time and by volume. It may be that PC + USB male is too busy, CPU is 100%, or PC + USB male has no time concept, clock is wrong. It is also possible that PC + USB male is lazy, each time put two goods, and then wait for two units of time .... because it is data transmission, in essence, everyone can understand it as copying data from a PC to a mobile hard disk. However, there is a very strict requirement that data of the same number of bytes must be copied per second, in addition, the data should be divided into 1/44100 equal points for timely transmission.
 

Or the explanation on the fifth floor

2. jitter I understand this as follows: assume that I and a singer A, I throw a piece of paper to a every minute, and some songs are written in the paper, A is a professional who knows how to sing. The length of the song in this paper is 1 minute. Under normal circumstances, I threw one every minute, and then a sang for one minute, it's a pretty smooth Song (you don't need to change the corners of the paper if you're not so fast ). However, sometimes there is a problem with the music time tuning in the paper I wrote, and it is inevitable that the hand is shaking, so a will inevitably have a problem when it is sung; sometimes I throw something on time, for example, 10 seconds late, so a's overall tuning is also problematic. This is what I understand as two jitter types. Sometimes, some words in the paper I handed in are wrong. If there is only one or two words, a can basically Guess according to the common sense of the statement. This is the basic error code correction.AlgorithmBut if you don't know what to write, then the tragedy will make everyone hear a say, "Cao! Shit !" This is a burst of sound. This is not saved, because a won't tell me to throw it again, that is, the error-free retransmission protocol. So the error code (wrong writing) is not the same as the jitter (not working on time ).
 

In a word, jitter means that the correct sound is not played at the right time.

2. upgrade from normal Audiovisual Devices to entry-level hifi equipment.

According to my research, this is to analyze the specific situation. for example, changing a line can solve the annoying background noise problem. but in general, the first change from an ordinary audio-visual device to hifi is the speaker. The investment of several hundred dollars can produce very large results immediately. The second is the sound card, the last is the power amplifier and decoder. the first two steps are for upgrade. the next two steps are for function splitting. this also conforms to the general rules of transactions.

As for the investment ratio of funds, this is a barrel principle. generally, there is no need to configure an independent sound card for a speaker of less than 100. The price of the sound card to the speaker is between and, and the ear is 0.5-2 times of the earphone, sound Card + DAC should not exceed the sum of headset and in-ear monitoring.

Iii. Pot and Tuning

The speaker is a mechanical device, which means that a new speaker has a grinding period. The process of running in the speaker is called the pot. The correct pot can maximize the potential of the speaker.

Different equipment is produced by different manufacturers, which also produces different styles. For example, in terms of headphones, senhaiiser's products are soft, delicate, dynamic, balanced, and sedated, with the widest adaptability, classical, especially the symphony music, is a masterpiece, while the power of byte is calm, high resolution, great dynamics, balance, and wide adaptation. It is suitable for classical, metallic rock, newage (high transparency), well-recorded fever records, etc. It optimizes the music environment through different equipment matching and equipment parameter settings.

The last is the human problem, which is also the most difficult problem to solve. you like fashion. He liked classical, but he was in a bad mood yesterday and listened to a rock roll. haha, this is basically not scientific, but belongs to the scope of metaphysics.

Put a picture at the end, as the basic summary of this article:

 

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