I’m so excited about this next product, Judy, that I can hardly contain myself. It’s a computer card that puts the whole world of sound right at your fingertips.
That’s right, Jim–this little card is an audio digitizer, audio mixer, synthesizer, power amplifier, mike preamp, MIDI interface, joystick interface and CD-ROM controller, all in one! Whew!
C’mon, Judy–you must be pulling my leg! How can one card do all that?
JUDY(SHAKING HEAD IN MOCK AMAZEMENT)
I find it hard to believe too, Jim! But thanks to space age technology, it’s all right here in this little wonder called a "sound card." (RAISES HANDS AND SHRUGS) It’s a miracle!
JIM(POINTS AT CAMERA)
Now viewers, listen close. You might expect to pay six or even seven thousand dollars for all those features. But if you call now, the Miraculous Miracle Sound Card is yours for only $229. That’s right–just $229!
And if you’re one of the first 40 callers…
Sound like just another inflated sales pitch? Not this time. Though perhaps not deserving of the word "miracle," the average computer sound card is an amazingly versatile product. And unless you’re planning to carve out your niche in silent videos, a sound card is a must-have for PC-based videographers. It comes as a surprise to many that the majority of nonlinear editing cards, especially those in the under-$1000 price range, do not have sound support built in.
Sound cards are not only for nonlinear editing–even folks with the simplest "two-finger" editing system can use a sound card to aid in their productions. With an inexpensive sound editor (often included with the sound card), you can do almost unlimited drag-and-drop editing of sounds. The sound card’s built-in synthesizer means you can create your own music or sound effects, running the card’s output to a mixer or record deck. Most sound cards include a MIDI interface; with this, you can enjoy the improved sound quality of a MIDI keyboard or synthesizer for your music. With the sound card’s built-in mixer, you can combine two or more external sound sources during editing.
In the next few pages, we’ll explore what a sound card is, how it works, and how to pick the best type of card for your needs. We’ll concentrate on those features that allow a sound card to record, play back or generate sound and music.
Different Cards for Different Modes
It’s worth noting that you may not need to buy a sound card at all. If your computer is a "multimedia" model, you probably already have the ability to record and play back sound. And most Macintosh computers will also handle sound right out of the box. But that doesn’t mean you can’t upgrade your multimedia PC or Macintosh’s sound capabilities for better performance or flexibility.
There are two main styles of audio card that PC owners will run across. General-purpose multimedia cards offer good sound quality with a wealth of features. Higher-quality audio-only cards are designed exclusively for audio recording.
Multimedia sound cards record and play back audio, but also allow you to play games, attach a joystick or control a musical-instrument digital-interface (MIDI) synthesizer. These cards are well-suited for video production, and you may find good use for their other features as well. The main drawback with many of the general-purpose cards is the limited flexibility of their audio inputs and outputs.
These cards will work as a simple audio mixer. Most offer both line and microphone inputs, the latter having a preamp to boost the level of the mike signal. With the audio mixer software provided with the card, you can blend these two inputs and send the completed mix to the card’s stereo output. Most sound cards will allow you to blend in music or speech from the on-board synthesizer as well. Sound cards usually lack the inputs to do serious audio mixing, but being able to blend a few inputs may be just the ticket for some videos.
Cards designed specifically for audio recording offer excellent sound quality with few bells and whistles. The primary advantage of these cards lies in how they connect with other audio equipment. Many audio-only cards offer four or even eight individual outputs. These can make controlling your audio easier with a dedicated mixer. Some cards offer dedicated signal processing (DSP) right on the board. This allows you to alter the tone or dynamic range of your sounds. Some DSP-equipped cards allow you to add real-time effects like reverb or delay.
Regardless of what style of card you end up with, your linear- or nonlinear-editing package will most likely control it through standard software drivers. This makes it easy to integrate almost any type of sound card into your system.
From Sounds to Bits
At the heart of a sound card is the audio digitizer. A digitizer turns an analog waveform–in this case, sound–into a series of numbers. The computer can then manipulate these numbers, store them on a drive and copy them without quality loss. On playback, the card converts the numbers back into an audible signal (see figure 1).
Sound cards allow you to adjust the fidelity of the recording–the tradeoff is hard-drive storage space. For example, CD-quality stereo audio takes up many times the drive space of telephone-quality mono sound. If you can get by with lesser-quality audio, you can fit more of it on your hard drive. And your computer will have an easier time processing and playing back these smaller audio files.
There are three parameters you can adjust on a sound card to tailor your audio quality. The first step is to choose whether you’re digitizing in stereo or mono. Capturing in stereo doubles the file size, and increases the demand on your computer. The second parameter is sampling rate. This tells the computer how often to "measure" the analog signal and store a numerical value. Audio sampling rate has a direct impact on the frequency response of your recordings; the sampling rate must be double that of the highest frequency you want to capture. An 8kHz sampling rate, for example, will only capture frequencies up to about 4kHz. Hence, the lower the sampling rate, the more "dull" your audio sounds.
The last parameter is bit depth or "word length." This sets how many bits the computer uses to store each measurement of the audio signal. The more bits used, the more accurate the recording (and the larger the resulting file). Using fewer bits can make for a coarse-sounding, noisy recording. For more on these quality tradeoffs, see figure 2.
How you set your sampling rate and word length are the greatest factors in digital audio quality, but they’re not the only ones. The design of the card itself plays a large role in how it sounds. Poorly designed cards can introduce unwanted noises into your audio due to inadequate shielding. The analog-to-digital (A/D) and digital-to-analog (D/A) converters used in the card also contribute to its sound quality. In general, though, even inexpensive sound cards should deliver sound quality on par with VHS-family hi-fi audio and 8mm-family AFM and PCM audio.
The Right Connection
Most multimedia sound cards use minijacks (1/8-inch phone plugs) for all inputs and outputs. These tiny connectors are the same ones found on personal stereos and camcorder headphone outputs. Their small size makes them a real plus for the cramped back panel of a computer card, but these jacks are not especially rugged or dependable. Some cards use RCA-style connectors for line-level inputs and outputs.
Multimedia sound cards usually have three or four connectors on their back panels. One is a microphone input (often using a mono minijack) which amplifies the weak mike signal. A stereo minijack often functions as a stereo "line-in" connector. This input accepts a line-level signal from another electronic device, such as a VCR or CD player. Don’t get these inputs confused–using the wrong one will guarantee unusable audio. Plug a mike into a line input, for example, and you’ll most likely get silence. Run a line-level signal into a mike input, and you’ll have massively distorted audio.
Outputs on multimedia sounds cards take two forms. The first is a "powered" output suitable for driving stereo headphones or multimedia speakers. Often found on a stereo minijack, this powered output may cause distortion if run into a VCR or mixer. Some sound cards have a hardware volume control on the back panel of the card, while others offer software control only. Power output from either type is pretty meager–don’t expect to fill a room with sound from your multimedia speakers.
For recording the sound card’s output, use the stereo "line out" connector (usually a stereo minijack as well). This output is rarely designed to run speakers, and plugging speakers in to it may damage the card. Some cards have a single output that does double-duty for both speaker and line output; these cards usually offer a hardware or software switch to toggle between output modes.
Audio-only cards rarely use minijack connectors, instead relying on larger, sturdier 1/4-inch jacks. Some even offer professional XLR-style balanced connections in a separate "breakout" box or cable. Audio-only manufacturers assume that you already have speakers, power amps and other audio components in your edit system. Instead of packing all this on one card, they give you uncompromised connections to your other audio gear.
As we enter the digital age, digital audio inputs and outputs are showing up on more multimedia and audio-only cards. Digital connectors are useful when capturing from or playing back to another digital audio device, such as a MiniDisc or Digital Audio Tape (DAT) recorder. By connecting digital output to digital input, you improve audio quality by bypassing the A/D or D/A conversion. Some audio-only cards will interface directly with a digital eight-track recorder, passing eight channels of audio down a single digital connection.
Bring on the Options
As Judy so amply (and breathlessly) explained, multimedia sound cards do much more than simply record and play back audio. "But," you’re probably asking, "do those other capabilities really offer anything to the home videographer?" You may be pleasantly surprised.
First off, multimedia sound cards do much more than just record audio–they generate it as well. The ability of a sound card to create music or sound effects can come in handy when it’s time to spice up your video soundtrack. If you’re musically inclined, you can purchase an inexpensive sequencer software package and use the sound card like a synthesizer. You can play your masterpiece into your computer with a MIDI keyboard, or you can place notes right on a traditional music staff. Because most multimedia sound cards have a MIDI input, you need only purchase an inexpensive MIDI keyboard to begin making your own music. Once you’ve got your music sounding the way you want it, you can record it to audio tape, videotape or disk.
If you’re not into making music, the synthesis capabilities of the sound card can still be an asset. You can purchase MIDI song files for almost any style of music, even today’s popular hits. Load an instrumental song into a sequencer, and you can modify it in any way. You can adjust the song’s key, tempo, dynamics, length, even make the song seamlessly repeat over and over. (You’ll still have to license the song to use it legally. See "Sound Tracks" in the December 1996 issue for more information.)
If you don’t want to deal with copyright issues, your sound card can still make beautiful music for your videos. Music generation software will churn out endless music in various styles, all of it license-free. You can make as many adjustments to the music as you wish, or you can let the software do its thing without any help at all. The resulting music isn’t the most creative or inspired stuff you’ve ever heard, but it’s yours. Also called algorithmic music composition software, these packages are available for under $100.
Because most multimedia cards offer MIDI output as well as input, you can use your sound card to drive external synthesizers and samplers. You can buy a great-sounding external synthesizer for a few hundred dollars; this may breathe new life into a sequenced music track. In most cases, you can combine sounds from the card with those from the external synthesizer.
Multimedia sound cards can draw on several different methods to create sounds. The first is true synthesis, where the card creates sounds from scratch. Often using a method called frequency modulation (FM), these inexpensive cards aren’t very convincing when trying to simulate acoustic instruments. But for spacey, ethereal sounds and effects, they do very well.
Wavetable synthesis adds actual sound recordings (or samples) to the sound card’s repertoire. Because these samples come from real instruments, wavetable sound cards achieve a much higher degree of realism. Disadvantages? They cost a bit more, primarily due to the memory required to store the samples.
Many multimedia cards offer a combination of both synthesis and sample-based sounds. These cards can generate FM sounds, sampled sounds, or mix the two together for the best of both worlds. Many sound cards allow users to attach a sample-based daughterboard, effectively upgrading a synthesis-only card to a sample-based model. Several pioneers of audio sampling (Kurzweil, Ensoniq, E-MU Systems) make such upgrade cards, and the improvement in sound quality is striking.
Another potential disadvantage of sample-based cards is that they’re only as good as the sounds the manufacturer put on them to begin with. There’s at least one notable exception to this, however–the Adobe Soundfonts system. Soundfonts allow you to download samples from the web or other source, storing them on the sound card. This makes the sound card somewhat obsolescence-proof, and insures that you’re not locked in to the sounds your card originally came with.
Whether it’s a multimedia Swiss-army knife or an audio-only model, a sound card packs a lot of audio power into a small package. These capabilities will only expand in the future, as sound cards deliver higher-fidelity audio, more-realistic sounds, better on-board processing and surround-sound recordings.
Learn the ins and outs of the sound card, and your videos may never sound the same again.