Sound Card Overview (Part 1)

As a symbol of multimedia computers, the history of sound cards is far less than that of other PC hardware. However, the author feels that at the beginning of this topic, it is very meaningful to review the sound card technology development process. This is conducive to a more comprehensive understanding of the technical characteristics and development trends of sound cards.

1. From PC speakers to ADLIB music card

Before sound cards were invented, PC games had no sound effects. Even if there is, it is the kind of "pickles" shrill sound from the small PC speaker. Although the effect is poor, it was very satisfying in that era. It was not until the birth of the ADLIB sound card that people enjoyed the truly pleasant computer sound effects.

The ADLIB sound card was developed by the British company ADLIB AUDIO. The earliest product was launched in 1984. Its birth was a precedent for computer audio technology, so ADLIB is a veritable "father of sound card". Because it is an early product, it has many deficiencies in technology and performance. Although we call it a "sound card", its function is limited to providing music without sound effects, which is a very regrettable flaw. Because the ADLIB sound card is really a "far away" thing from us, I cannot find more technical parameters and product information, but we must recognize the importance of the word "ADLIB" in the multimedia field. For quite some time, ADLIB's sound card was an important standard in the multimedia field. It was not until the rise of CREATIVE that ADLIB gradually rolled out the stage of history. Nowadays, it is difficult for us to see their products on the market, but the location of ADLIB still remains in the driver information database of Windows, so we can see its glorious past.

2. Sound Blaster series-the beginning of the CREATIVE era

Nowadays, when it comes to the famous CREATIVE company, it can be said that no one knows, no one knows. People from Hong Kong and Taiwan translated it as "creating a giant, creating a pass," and we call it "innovation" in China. All along, in the minds of many enthusiasts, CREATIVE has almost become synonymous with sound cards. But as we mentioned earlier, the father of the sound card is ADLIB, not CREATIVE. So how does the innovative company establish itself as the leader in the multimedia field? This starts with the Sound Blaster sound card.

The Sound Blaster sound card (Sound Blaster Card) is the first generation sound card product launched by CREATIVE in the late 1980s, but it is much stronger in function than the earlier ADLIB card. Its most obvious feature is that it combines the duality of music and sound effects. Processing power is proud of CREATIVE, so Sound Blaster has an epoch-making significance in the development of sound cards. Although it only has an 8-bit, mono sampling rate (we will introduce the sampling rate and other technical concepts later in the article), the accuracy of the sound playback is low, but it makes people use it for the first time on the PC. I got a double auditory enjoyment of music and sound effects, which was very popular in those days. Since then, CREATIVE has launched a follow-up product-Sound Blaster PRO, which adds a stereo function and further enhances the audio processing capabilities of the PC. Therefore, the SB PRO sound card was incorporated into the MPC1 specification (the first generation multimedia standard) at the time, and became the object of pursuit by enthusiasts.

After achieving the perfect combination of music and sound effects, CREATIVE did not meet the status quo, they seek new breakthroughs in technology. As mentioned earlier, both Sound Blaster and Sound Blaster PRO only have an 8-bit signal sampling rate, which we can directly understand as a rough sound quality. Although SB PRO has stereo processing capabilities, it still cannot make up for the shortcomings caused by sampling loss . The introduction of Sound Blaster 16 has completely changed this situation. It is the first sound card with 16-bit sampling precision. People can finally achieve CD sound quality signal recording and playback through it, making the sound card audio quality reach an unprecedented height. . After a considerable period of time, Sound Blaster 16 became the next-generation standard for multimedia audio.

From Sound Blaster to SB PRO, to SB 16, CREATIVE gradually established itself as the dominant sound card. During the development of technology and cost reduction, the sound card has been able to reach a high level of luxury (early sound cards are very expensive), and gradually became the standard configuration of ordinary multimedia computers.

3. SB AWE series sound card-MIDI shock wave

The development of Sound Blaster series sound card to SB 16 is already a very mature product system. But SB 16, like SB and SB PRO, uses FM synthesis technology in MIDI (Electronic Synthesizer), which is relatively monotonous for the composition of music. In the mid-1990s, a technology called "wave table synthesis" began to become popular, far surpassing FM synthesis in audition effects. CREATIVE launched the Sound Blaster Awe 32 sound card with wavetable synthesis in 1995. SB Awe 32 has a 32-voice wavetable engine, and integrates a 1MB capacity sound library, making its MIDI synthesis effect greatly surpasses all previous products.

However, people have come into contact with some professional MIDI wavetable synthesizers and found that although the effect of Awe32 is much higher than that of FM, it is far from reflecting the true charm of MIDI. The main reason is that the sound library is too small. Based on this, CREATIVE launched the Sound Blaster Awe 64 series in 1997. Among them, the "heavy stick bomb"-SB Awe 64 GOLD has 4MB wave table capacity and 64 polyphony support. height. Of course, the price of this classic sound card is also quite expensive.

As a product series coexisting with the SB 16 series, Awe32 and Awe64 have put a lot of effort into MIDI synthesizing ability, but since this performance improvement needs to increase product cost, the real market response is not good.

4. PCI sound card-the beginning of a new era

From Sound Blaster to SB Awe 64 GOLD, the sound card is always in the form of ISA interface. However, with the further development of technology, the small data transmission capability of the ISA interface has become a bottleneck in the development of sound cards. Transferring the interface form from ISA to PCI has become the general trend of sound card development. The PCI sound card theoretically has the function of increasing the transmission channel (ISA is 8MB / s, PCI can be up to 133MB / s), and the function of improving data broadband. Therefore, the realization of three-dimensional sound effects and DLS technology on the sound card has improved the performance of the sound card in many ways, but the overall cost can be greatly reduced, which is the best of both worlds. Right now the main product of CREATIVE-Sound Blaster Live! Series is the most typical high-end PCI sound card product, representing today's higher technical level.

The four product stages introduced by the author above can be said to represent a brief history of sound card development-ADLIB pioneered the sound card technology; Sound Blaster integrated music and sound effects for the first time; SB PRO and SB 16 complete this series SB Awe 32 and Awe 64 pioneered new wavetable synthesis technology; the emergence of PCI sound card marks the continuous emergence of new technologies and new challenges.

Perhaps attentive readers will find that the history of sound card development is like a history of CREATIVE product upgrades. This is because CREATIVE has always been in a leading position in technology, so "Sound Blaster" has always dominated among various multimedia standards. However, as with the development of other hardware products, with a "mainstream brand", many "compatible brands" will inevitably be created. Many manufacturers see the profitability in the multimedia field, and they have joined the design and development of compatible sound card chips, which has generated mutual competition between manufacturers and is very beneficial to promote the development of the market. Among these compatible chip developers, the more famous ones are ESS and YAMAHA.

ESS is a company specializing in the development of audio and video communication semiconductors. Its compatible sound card chips have always had a good reputation among users. For example: ESS-688, ESS-1869, etc. are all popular Sound Blaster 16 compatible chips. The name of YAMAHA may be more familiar to everyone. Its status is very important in the field of electronic musical instruments. So from the ADLIB sound card period, Yamaha has firmly controlled the share of the sound card's MIDI synthesizer part in his own hands. ADLIB cards generally use YAMAHA's OPL-2 FM synthesizer, while the Sound Blaster series (including PRO type and 16 type) all use OPL-3 FM synthesizer. At the same time, YAMAHA also independently developed the main chip of the sound card, and YMF-719 is a model for the SB16 era. Of course, there are such as ALS, Crystal, OPTI, etc., also have a certain market share.

In recent years, many new sound card chip development and design manufacturers have emerged, which objectively played a role in further intensifying market competition. And with the rapid development of technology, manufacturers are no longer limited to products compatible with CREATIVE in performance, but strive to obtain their own characteristics and development space. It is foreseeable that in the future, the sound card will develop towards the diversification of functions and the digitization of sound signals. I believe tomorrow's sound card will bring us more surprises. CREATIVE's history of dominating the world will be gone forever.

Part II Basic terminology analysis

I believe that some readers have some headaches when they see the professional vocabulary such as "sampling rate, FM synthesis, wavetable synthesis" in the first part. In the second part of the following, I will focus on explaining these professional vocabulary for everyone, and strive to be simple.

1. About sound sampling

One of the main functions of the sound card is to record and play back sound information. In this process, the number of sampling bits and the sampling frequency determine the quality of sound collection.

1. The number of bits sampled

The number of sampling bits can be understood as the resolution of the sound card processing sound. The larger the value, the higher the resolution, and the more realistic the recorded and replayed sound.

We must first know that the sound files in the computer are represented by the numbers 0 and 1. So the essence of recording on a computer is to convert analog sound signals into digital signals. Conversely, during playback, the digital signal is restored to an analog sound signal for output. The sound card bit refers to the binary digits of the digital sound signal used by the sound card when collecting and playing sound files. The position of the sound card objectively reflects the accuracy of the description of the digital sound signal to the input sound signal. 8 bits represent 2 to the 8th power-256, and 16 bits represent 2 to the 16th power-64K. In comparison, for a piece of the same music information, a 16-bit sound card can divide it into 64K precision units for processing, while an 8-bit sound card can only process 256 precision units, resulting in a large signal loss. The final sampling effect is naturally Incomparable.

Nowadays, all mainstream products on the market are 16-bit sound cards, not 64-bit or even 128-bit advocated by some ignorant merchants. They confuse the concept of polyphony with the concept of sampling digits. Today's most powerful sound card series-Sound Blaster Live! Although the EMU10K1 chip is claimed to be 32-bit, it is only a multi-audio streaming technology based on Direct Sound acceleration. Its essence is still a 16-bit sound card. It should be said that 16-bit sampling accuracy is more than enough for computer multimedia audio.

2. Frequency of sampling

Sampling frequency refers to the number of times the recording device samples the sound signal in one second. The higher the sampling frequency, the more realistic and natural the sound will be. In today's mainstream sound cards, the sampling frequency is generally divided into three levels: 22.05KHz, 44.1KHz, and 48KHz. 22.05 can only achieve the sound quality of FM broadcasting, 44.1KHz is the theoretical CD sound quality limit, and 48KHz is more accurate. . The human ear cannot recognize the sampling frequency higher than 48KHz, so it has little use value on the computer.

Second, the concept of the number of channels

The number of channels supported by the sound card is also an important sign of technological development. From mono to the latest surround sound, let's take a closer look.

1. Mono

Mono is a relatively original form of sound reproduction, and early sound cards were more commonly used. When playing back mono information through two speakers, we can clearly feel that the sound is transmitted from the middle of the two speakers to our ears. This kind of recording method lacking in position is naturally lagging behind with the current eyes, but when the sound card was just started, it was already a very advanced technology.

2. Stereo

Mono lacks positioning of sound, and stereo technology has completely changed this situation. The sound is allocated to two independent channels during the recording process, thus achieving a very good sound localization effect. This technique is especially useful in music appreciation. The audience can clearly distinguish the direction from which various instruments come, so that the music is more imaginative and closer to the live experience. Stereo technology is widely used in a large number of sound cards since Sound Blaster Pro, and has become a far-reaching audio standard. Today, stereo is still the technical standard followed by many products.

3. Quasi-stereo

The basic concept of a quasi-stereo sound card is to use mono when recording sound, and the playback is sometimes stereo and sometimes mono. Sound cards using this technology have been popular on the market for some time, but now they have disappeared.

4. Four-channel surround

People's desires are endless. Although stereo sound meets people's requirements for the left and right channel position experience, with the further development of technology, everyone gradually finds that dual channels have become more and more unable to meet our needs. In the first part of the topic, the author mentioned that the large bandwidth of PCI sound cards has brought many new technologies, among which the most rapid development is the three-dimensional sound effect. The main purpose of the three-dimensional sound effect is to bring people a virtual sound environment, and create a sound field that is more realistic through the special HRTF technology, so as to obtain better game listening effects and sound field positioning (more on this later). To achieve good results, it is not enough to rely on two speakers, so the stereo technology is stretched in front of the three-dimensional sound effect, and the new four-channel surround audio technology solves this problem well.

The four-channel surround specifies four pronunciation points: front left, front right, rear left, and rear right, and the audience is surrounded in the middle. At the same time, it is also recommended to add a subwoofer to enhance the playback processing of low-frequency signals (this is why the 4.1-channel speaker system is widely popular today). As far as the overall effect is concerned, the four-channel system can bring the sound surround from multiple different directions to the listener, can obtain the hearing experience of being in various different environments, and give the user a brand-new experience. Nowadays, four-channel technology has been widely integrated into the design of various high-end sound cards, becoming the mainstream trend in the future.

5.5.1 channel

5.1 channels have been widely used in various traditional theaters and home theaters. Some well-known audio recording compression formats, such as Dolby AC-3 (Dolby Digital) and DTS, are based on the 5.1 sound system as the technical blueprint. In fact, 5.1 sound system comes from 4.1 surround, the difference is that it adds a center unit. This central unit is responsible for transmitting sound signals below 80Hz, which is conducive to enhancing the human voice when watching the film, and concentrates the dialogue in the middle of the entire sound field to increase the overall effect. I believe that everyone who has truly experienced Dolby AC-3 sound effects will be impressed by the 5.1 channel.

Do n’t think that 5.1 is already the pinnacle of surround sound. The more powerful 7.1 system is already eager to try. On the basis of 5.1, it has added two pronunciation points of middle left and middle right, in order to achieve a more perfect state. Of course, due to the relatively high cost, it will take time to become popular, so I won't introduce it here.

Three, three-dimensional sound effect concept

As the emerging technology that many sound cards are pursuing now, let's take a closer look at the mystery of the three-dimensional sound effects that have been fired.

1.3 The difference and relationship between the audio API and HRTF

API is the meaning of programming interface, which contains many instructions and specifications about sound localization and processing. Its performance will directly affect the expressiveness of 3D sound effects. Today's popular APIs include Direct Sound 3D, A3D, and EAX. HRTF is the English abbreviation of "Head Related Conversion Function", and it is also an important factor for achieving three-dimensional sound effects. Simply put, HRTF is a sound localization algorithm, and its actual role is to deceive our ears. At present, there are many sound chip design manufacturers and research departments in related fields participating in the development and design of this algorithm. Although the principles are similar, but due to the slightly different methods in the analysis and research process, there will be more or less performance differences between various HRTF algorithms. It's easy to confuse API with HRTF. In fact, the two are fundamentally different and related to each other.

To give an example: A3D is one of the most popular 3D audio APIs nowadays, most of the mainstream PCI sound cards now support A3D 1.0. But some users will reflect, why my XXX sound card claims to support A3D, but why the actual effect is not as good as the friend's DIAMOND S90? The reason is that S90 uses Aureal's own AU8820 chip, and the HRTF algorithm used is naturally derived from Aureal; while the XXX sound card does not use the AU8820 chip, but uses other HRTF algorithms, although it can also support A3D function changes, but because of The algorithm is inherently inadequate and needs to be transformed by function. Naturally, it cannot be compared with S90 in effect. Therefore, many sound cards now claim to support A3D, EAX, and DS3D, which can only show that it supports these specifications and instructions. The actual effect depends on the HRTF algorithm used by the chip. Before purchasing a sound card, it is very important to understand what kind of HRTF algorithm its chip uses for the final 3D sound effect.

2. Main 3D audio PAI

(1) Direct Sound 3D-the old audio API derived from Microsoft DirectX. For sound cards that cannot support DS3D, its role is a three-dimensional sound HRTF algorithm that requires CPU, so that these early products have the ability to handle three-dimensional sound. But from the perspective of actual effect and execution efficiency, it is not satisfactory. Therefore, the sound cards introduced thereafter have a so-called "hardware support DS3D" capability. DS3D has become an API interface on this type of sound card, and its actual hearing effect depends on the strength of the HRTF algorithm used by the sound card itself.

(2) A3D-developed by American company Aureal, divided into 1.0 and 2.0. Version 1.0 includes two major application areas of A3D Surround and A3D Interactive, with special emphasis on real sound field simulation under stereo hardware environment. 2.0 added sound wave tracking technology on the basis of 1.0 to further enhance performance. It is the best 3D audio technology for positioning today.

(3) EAX-is CREATIVE's new signboard, meaning "environmental sound effect expansion set". EAX is built on DS3D, but several unique sound effect commands are added to the latter. The EAX feature is to focus on rendering various sound changes and performance under different environmental conditions, and the sound positioning ability is not as good as A3D, so EAX recommends that users equip a 4-channel surround speaker system.

3. The main HRTF algorithm.

Large companies such as Aureal and Creative can not only develop powerful instruction set specifications, but also develop advanced HRTF algorithms and integrate them in their own chips. The CRL and QSound introduced below are mainly for the sale and development of HRTF algorithms, and they do not introduce instruction sets.

The HRTF algorithm developed by CRL is called Sensaura and supports most mainstream 3D audio APIs including A3D 1.0 and EAX and DS3D. And this technology has been widely used in ESS, YAMAHA and CMI sound card chips, which has become a relatively influential technology, from the actual audition effect is indeed good. The Q3D developed by QSound can provide an environment simulation function similar to EAX, but the effect is still relatively simple, which is slightly inferior to Sensaura's large and comprehensive performance indicators.

4. About MIDI

MIDI is synonymous with computer music and came out in the early 1980s. What exactly is MIDI? Let us explore together.

1. The concept of MIDI

MIDI is the abbreviation of Musical Instrument Digital Interface, which means the digital interface of music equipment. It is a unified communication protocol between electronic musical instruments and between electronic musical instruments and computers. We can broadly interpret it as a general term for electronic synthesizers and computer music, including protocols, devices, and other related meanings.

2. The essence of MIDI files

Right now in some game software and entertainment software, we can often find many music files with MID and RMI extensions. These are the most commonly used MIDI formats on computers. The MIDI file is a descriptive "music language", which expresses the music information to be played in bytes. For example, "At a certain moment, what instrument to use, what note to start with, what tone to end with, what accompaniment to add", etc., so the MIDI file is very compact.

3.FM synthesis

Since the MIDI file is just a description of the music, it does not contain any sound information for playback, so how is a beautiful computer music played by our sound card? This will require a variety of synthetic means. Earlier ISA sound cards generally used FM synthesis, which is "frequency modulation". It uses the principle of sound oscillation to synthesize MIDI. However, due to the limitations of the technology itself, coupled with the fact that most of these sound cards use cheap YAMAHA OPL series chips, the effect is naturally not good.

4. Wavetable synthesis

The English name of the wave table is "WAVE TABLE", which literally translates to "wave table". In fact, it is to record all the sounds (including various ranges and tones) that can be produced by various real musical instruments and store them as a wave table file. During playback, according to the music information recorded in the MIDI file, a command is given to the wave table, and the corresponding sound information is found one by one from the "table", which is synthesized and processed and played back. Since it uses sampling of real instruments, the effect is naturally better than FM. The sound information of musical instruments of general wavetables is recorded with 44.1KHz and 16Bit precision to achieve the most realistic playback effect. Theoretically, the larger the wave table capacity, the better the synthesis effect.

5. The meaning of polyphony

In the naming of various sound cards, we often find numbers such as 64 and 128. Some users and even merchants mistake them for 64-bit and 128-bit sound cards. In fact, as far as the current technological development is concerned, the sound card has not been developed, nor is it necessary to develop such a high data processing channel. 64 and 128 represent only the maximum number of polyphony that this card can achieve during MIDI synthesis. The so-called "polyphony" refers to the maximum number of sounds produced by MIDI music in one second. If the polyphony value supported by the wavetable is too small, some complex MIDI music will have some parts lost during synthesis, which directly affects the playback effect. Fortunately, most wavetable sound cards today provide more than 64 polyphony values, and most MIDI polyphony numbers do not exceed 32, so the phenomenon of timbre loss will not occur.
Another thing to note is the difference between "hardware supports polyphony" and "software supports polyphony". The so-called "hardware-supported polyphony" means that all the polyphony numbers are generated by the sound card chip, and "software-supported polyphony" is to increase the number of polyphony by software synthesis on the basis of "hardware polyphony", but this is Need CPU to drive. At present, the largest hardware polyphony supported by mainstream sound cards is 64, while the software polyphony can be as high as 1024, which is amazing!

6. The role of DLS technology

The advent and popularization of PCI sound card brought a little "revolution" of wavetable synthesis, the key lies in the application of DLS technology. DLS is called "Down Loadable Sample", which means: a sample sound library available for download. Its principle is quite similar to that of a soft wave table. It also stores the sound library in the hard disk and transfers it to the system memory when it is played But the difference is that after using DLS technology, it does not use the CPU to calculate when synthesizing MIDI, but relies on the sound card's own audio processing chip for synthesis. The reason is that the data bandwidth of the PCI sound card reaches 133Mb / sec, which greatly widens the system memory. The transmission channel between the sound card and the sound card. This not only eliminates the sound library memory required by the traditional ISA wave table sound card, but also greatly reduces the CPU occupancy rate when playing MIDI. And this wave table library can be updated at any time and use DLS The timbre editing software is modified, which is an advantage that traditional wavetables cannot match. (To be continued)

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Sound Card Overview (Part 2)

As far as a sound card is concerned, the status of the audio processing chip is not ...

Published on 2006-04-17 23:39 • 1245 times read