What is the audio card? What are the main functions of the audio card?
The audio card is the most basic component of multimedia technology and is the hardware that realizes the mutual conversion of acoustic/digital signals.
How the audio card works: The working principle of the audio card (sound card) is actually very simple. We know that the microphone and the speaker use analog signals, and the computer can process digital signals. The function of the audio card (sound card) is Achieve the conversion between the two. According to the structure, the audio card (sound card) can be divided into two parts: an analog-to-digital conversion circuit and a digital-to-analog conversion circuit. The analog-to-digital conversion circuit is responsible for converting an analog sound signal collected by a sound input device such as a microphone into a digital signal that can be processed by a computer. The digital-to-analog conversion circuit is responsible for converting the digital sound signal used by the computer into an analog signal that can be used by a device such as a speaker.
1, digital signal processing chip
The digital signal processing chip can perform various signal recording and playback tasks, and can also perform many processing tasks such as audio compression and decompression operations, changing the sampling frequency, interpreting MIDI instructions or symbols, and controlling and coordinating direct memory access (DMA) work. .
2, A / D and D / A converter
The sound originally appeared as an analog waveform and must be converted to digital form for use in a computer. To achieve this conversion, the sound card contains an A/D converter that converts the analog signal into a digital signal, allowing the data to be stored on disk.
In order to send the sound output signal to a speaker or other device for broadcast, the sound card must use a D/A converter to convert the digital representation of the computer into an analog signal.
3, bus interface chip
The bus interface chip transfers commands and data between the sound card and the system bus.
4, music synthesizer
The music synthesizer is responsible for synthesizing digital audio waveform data or MIDI messages into sound/
5, mixer
The mixer can mix different channels, such as microphone or line inputs, and CD input sound signals. In addition, the mixer provides the user with the ability to control the volume by software.
Audio card features(1) Enhancing the friendliness of the computer;
(2) involving a wide range of technical fields and low technical layers;
(3) Standardization of multimedia technology;
(4) Integration and instrumentation of multimedia technology.
1. Play digital music:
This is the most basic function of an audio card (sound card), thanks to improvements in the way digital music is stored. From the original wav to the popular mp3, in the emerging audio format such as wma, digital music is accepted by the majority of users. Listening to music while working has become the habit of most computer gamers. The original audio card (sound card) can only play a simple tone, and later on the 8-bit audio card (sound card), 16bit audio card (sound card), the computer is more and more suitable for playing music. At present, the most advanced audio card (sound card) pushes the maximum sampling rate supported by the audio card (sound card) to 192 kHz, and the size is also up to 24 bits. So we can enjoy MP3/CD or even DVD Audio on the computer.
2, recording:
This is also one of the most basic functions of an audio card (sound card), collecting signals from the microphone. At present, most civil audio cards (sound cards) can collect 48khz/16bit signals. Although many ordinary users don't care much about the audio card (sound card) recording function, it has to be said that this is a lot of fun. Features. With her, you can karaoke on your computer, entertain yourself, and enjoy yourself. If the audio card (sound card) recording quality is not bad, just need a better microphone, it is not difficult to make a personal album CD. With voice input software, it can also be used as a voice input method. At present, the high-end audio card (sound card) supports 96kHz/24bit recording, and the actual recording effect has reached a high level, which provides a better guarantee for the hardware environment of the home recording studio. Future computers are likely to implement voice control, which will also be related to audio cards (sound cards).
3. Voice communication:
When an audio card (sound card) has the ability to output and input signals, the audio card (sound card) becomes an important part of voice communication. If the audio card (sound card) can output and input signals at the same time, this audio card (sound card) supports the dual-full work mode, which is very suitable for voice communication on the network. The cost of voice communication on the Internet is unimaginably low. It is much cheaper than traditional telephones. If you want to communicate frequently across regions, using PC to PC voice communication is a very cost-effective way, thanks to the current network conditions. Improvement, communication quality has also been greatly improved, not worse than the traditional phone, only better. This will also be one of the development directions of future communications. On some audio cards (sound cards), there is even a selling point optimized for Netmeeting. The audio card (sound card) used for voice communication needs to support full duplex, that is, playback and recording can be performed simultaneously.
4, real-time effects:
When computer games become more and more 3D, users not only require 3D images, but also require the sound to simulate the real environment. Some of them have proposed 3D sound solutions, the most famous of which are Aureal's A3D, Microsoft DirectSound and Creative EAX. These proposals require audio cards (sound cards) to have very powerful computing power to simulate real sound effects. 3D game fans are also listening to all directions. The proposal of these schemes perfects the function of the audio card (sound card), and the entertainment of the audio card (sound card) is greatly enriched. The implementation of these functions is related to the ability of the audio card (sound card) to process signals. Not only do these sounds are needed in the game, but also in music appreciation. The famous Winamp player has many DirectSound real-time effects, listening to music. At the time, we can add the effects of echo, reverb and even the amplifier. The implementation of these effects also requires audio card (sound card) acceleration to support. Of course, the implementation of these effects does not necessarily require an audio card (sound card), which can be simulated by software, but hardware acceleration does not sacrifice performance.
5, interface card:
When using the analog mode to connect to the CD-Rom and play it, the sound card is an interface card, and the sound card will not do any processing other than the control level. At this time, the sound card is an interface card, which appears as an intermediary device. In connection with other analog devices, such as TV cards, the sound card is used as an interface card. In addition, when playing a DVD, when the sound card outputs the AC3 audio stream, it is only used as an interface card.
Early sound cards came with an IDE port that could be used to connect to an optical drive. Today's sound cards don't have this interface. At this time, the sound card is also an interface card.
In addition, most sound cards also come with a MIDI/game controller port for linking multimedia devices such as MIDI keyboards and gamepads. As the USB standard is increasingly accepted, the role of this port is gradually reduced, and more devices are used. USB standard connection.
As some old ports were eliminated, new port ports were introduced. The most notable is the SB1394 port included with the Audigy/Audigy2 series. The introduction of this port will greatly enhance the function of the sound card and can be connected to the IEEE 1394 standard. Interface external devices such as DV cameras, and can connect 63 computers for low-latency connected games. The SB1394 has a transfer speed of up to 400 Mbps, which is 30 times that of the USB 1.1 standard, enabling high-speed transfer of large files between the host and peripherals. This means that the network function of the sound card is imposed and will become a veritable multimedia interface center in the computer. Many models in Audigy/Audigy2 come with a remote control. When operating remotely, the sound card is also an interface card.
6, audio decoding:
In the digital audio world, there are a variety of coding schemes, most of which can be solved by software. When DVD-Rom became popular, people found that DVDs had much higher system requirements than VCDs, especially the audio part. In order to better be immersive, DVD movies mostly used AC-3/DTS. The way to encode its audio part, the algorithm is far more complicated than most of the previous audio coding, the software can decode, but more friends rely on hardware decoding. The newly launched Audigy2 ZS allows users to decode 5.1 matrices into 6.1 when playing normal DTS sound DVDs. These are all sound cards in action. In addition, most of the sound cards such as the CS4630 series support hardware MP3 acceleration. In fact, this is the result of the sound card participating in the decoding.
7, the synthesizer:
The effect of playing MIDI depends on the sound card's ability to synthesize. The sound card's ability to synthesize the wave table directly affects the performance of the sound card playing MIDI. The English name of the wave table is "WAVE TABLE", which is literally "waveform table". In fact, it records all the sounds (including the various ranges and tones) that can be produced by various real instruments and stores them as a wavetable file. During playback, the music information recorded by the MIDI file is sent to the wave table, and the corresponding sound information is found one by one from the "form", and is synthesized and processed and played back. This ability has been an important indicator of an excellent sound card. It is also an important indicator for manufacturers to sell high prices. The biggest difference between the SB AWE64 standard version and the AWE64 GOLD was the difference in wave table capacity. This is only the case, but the price gap is really amazing. of. Most sound cards now use DLS (DownLoadable Sample) wavetable synthesis technology. With the support of WDM driver, all sound cards can have better synthesis effect. Of course, the premise is that there must be a good DSL sound library. There is another kind of FM synthesis, which is basically eliminated because the synthesis effect is too monotonous.
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