Chapter 12 - Multimedia

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This chapter describes the multimedia architecture and features in Microsoft Windows 98. Windows 98 provides an immediate multimedia upgrade for users of multimedia applications and equipment in your organization. Its Plug and Play architecture makes it simple to install and operate compatible multimedia devices.

The 32-bit Windows 98 architecture ensures that Windows 98 multimedia titles can include digital video and sound of excellent quality. At the same time, Windows 98 is completely compatible with most 16-bit multimedia titles.

See Also

• For information about devices, see Chapter 24, "Device Management." 

• For information about Broadcast Architecture, see Chapter 13, "WebTV for Windows 98." 

• For information about Internet-related multimedia applications such as NetShow, see Chapter 20, "Internet Access and Tools." 

• For information about the Win32 Driver Model (WDM), see Chapter 30, "Hardware Management." 

Overview of Multimedia

Windows 98 contains several components to enhance your multimedia experience, whether you are creating, displaying, or simply playing titles. The multimedia features of Windows 98 include Microsoft DirectX®, the Media Control Interface (MCI), AutoPlay, and improved support for multimedia files and devices.

DirectX

Microsoft DirectX is a set of application programming interfaces (APIs) that allow applications to gain access directly to a system's multimedia hardware. The DirectX APIs included in Windows 98 can be broken down into the following components:

• DirectDraw®, a 2-D graphics interface, supports accelerated animation techniques by providing direct access to bitmaps in off-screen display memory as well as extremely fast access to the blitting and buffer-flipping capabilities of a computer's video adapter.

• DirectSound® provides an interface between applications and an audio adapter's sound mixing, playback, and capture capabilities.

• Direct3D®, a 3-D graphics interface, supports the 3D-rendering functionality built into modern display adapters.

• DirectPlay® allows for easy connectivity of games over a modem link or network.

• DirectInput® provides functionality to process input from joysticks, gamepads, keyboards, mice, Human Interface Device (HID) devices, and force feedback devices. Although DirectInput is similar to Windows 98 input components, it provides advanced joystick input capabilities for games and scalability for future Windows hardware input APIs and drivers.

• DirectAnimation™ makes it possible to have titles that combine different types of media, such as images, 3-D objects, sounds, movies, and text, where any or all the media types can be animated and respond to user input. DirectAnimation enables multimedia content on Web pages, on your desktop, and in standalone titles. 

• DirectShow™, formerly known as ActiveMovie™, provides support for a Digital Video Disk (DVD) Navigator/Splitter, proxy filters for video and audio streams, a video mixer, a video renderer, and an audio renderer. 

Media Control Interface

The Media Control Interface (MCI) provides applications created for Windows 98 with device-independent capabilities for controlling such media devices as audio hardware, videodisc players, and animation players. This interface works with MCI device drivers to interpret and run such MCI commands as pause, play, and stop.

MCI provides a set of core commands for a broad range of media devices. For example, MCI uses the same command to begin playback of a waveform-audio file, a videodisc track, and an animation sequence. It also provides extended commands for using particular device types with unique capabilities, such as a frame-based time format used in animation. For more information about MCI drivers and commands, see the Microsoft Windows 98 Device Development Kit.

A device type identifies a class of MCI devices that respond to a common set of commands. Table 12.1 lists the currently defined MCI device types.

Table 12.1 MCI device types 

Device type	Description
animation	Animation device
cdaudio	Compact disc (CD) audio player
dat	Digital audio tape player
digitalvideo	Digital video in a window (not graphics device interface [GDI]–based)
other	Undefined MCI device
overlay	Overlay device (analog video in a window)
scanner	Image scanner
sequencer	MIDI sequencer
vcr	Videocassette recorder or player
videodisc	Videodisc player
waveaudio	Audio device that plays digitized waveform-audio files

Multimedia Files

A multimedia file is usually maintained in one of the formats described in Table 12.2.

Table 12.2 Multimedia file formats 

Format	Corresponding file name extension
Video for Windows	.avi
Waveform-audio	.wav
Moving Picture (MPEG)	.mpg
Quick Time for Windows	.mov
Musical Instrument Digital Interface (MIDI)	.mid

Multimedia files are stored on a compact disc, a local hard disk drive, a network file server, or another storage medium. The amount of data that the storage medium can continuously supply to the file system for streaming formats constrains the playback quality.

A multimedia data stream (such as an AVI file) generally contains multiple components, such as digital-video data, audio data, text, and perhaps other data (such as hot spot information, additional audio tracks, and so on). As multimedia information is read from the CD-ROM drive, the multimedia subsystem determines what the data stream contains and then separates and routes the data accordingly.

To provide the best possible performance from double-speed and faster CD-ROM drives, Windows 98 includes the 32-bit CD-ROM file system (CDFS) for reading files from CD-ROM drives quickly and efficiently. For more information about CDFS, see Chapter 26, "Performance Tuning," and Chapter 28, "Windows 98 Architecture."

CDFS replaces most Windows version 3.1 MSCDEX drivers.

Support for Multimedia Devices

Built-in support for common multimedia authoring devices makes it easy to set up a computer for step capture, a process in which a user captures digital-video data one frame at a time; the data is usually compressed later. This is a slow process, but it results in the highest possible quality of digital video.

To play the contents of a videotape on a computer, you must connect the video and audio outputs from the VCR to the video-capture or overlay and to the audio inputs of the computer. You might also need to install an MCI digital-video device driver.

WDM Audio

WDM audio class architecture performs all audio processing in kernel mode. Any number of filters can be connected into the filter graph to manipulate audio/video streams. WDM also provides a more complete architecture than was possible earlier. Code common to all audio hardware on a given bus is now part of the operating system, making for faster development with more consistent results.

WDM audio supports the following features for games under Windows 98:

• Software emulation of legacy hardware to support MS-DOS-based games. WDM drivers, which run in kernel mode, provide virtual Sound Blaster Pro, MPU 401, and legacy joystick interfaces. 

• DirectSound support for software-simulated 3-D sound (interaural time delay and volume). 

• A wave-table General MIDI synthesizer entirely in kernel-mode software. This provides 32 voices of music synthesis with 22.05-kHz output. DirectShow, DirectMusic™, MMSYS, and virtual MPU 401 (via Sound Blaster emulation) can use the synthesizer functions. The architecture supports optimal configuration based on CPU performance and installed hardware. 

• A high-quality kernel-mode software sample rate conversion (SRC) capability, which converts data streams (including composite mixes of all 11.025-kHz or 22.05-kHz sources) to the final output mix format, typically 16-bit 44.1 kHz (general SRC support includes other rates). 

• A kernel-mode system-wide software mixer, which supports DirectSound, DirectShow, and MMSYS clients, as well as kernel-mode WDM filters, including CD-ROM and MIDI drivers. The mixer implements highly optimized pulse code modulation (PCM) mixing at 8-bit or 16-bit 11.025, 22.05, 44.1, and 48 kHz. 

• Flexible control of the output destination. The WDM drivers can send the master 16-bit 44.1-kHz or 48-kHz or other format output to an Industry Standard Architecture (ISA), Peripheral Component Interconnect (PCI), Universal Serial Bus (USB), or IEEE 1394 audio device. 

• Native 32-bit DirectSound support for simultaneous audio input and output, not dependent on 16-bit MMSYS components. 

WDM audio supports the following features for CD and DVD media playback under Windows 98:

• A kernel-mode, system-wide software mixer, which supports DirectSound, DirectShow, and MMSYS clients, as well as kernel-mode WDM filters, including CD-ROM and MIDI drivers. The architecture provides the ability for algorithms from any vendor to decode the DVD audio, and it supports mixing at any sampling rate from 100 Hz to 100 kHz. 

• Flexible control of the output destination. The WDM drivers can send the master 16-bit 44.1-kHz or 48-kHz or other format output to an ISA, PCI, USB, or IEEE 1394 audio device. Additionally, support is provided for redirection of the PCI-device final-mix output to USB speakers. 

• A kernel-mode CD-ROM driver that emulates MSCDEX commands and implements reading, parsing, and streaming of CD digital audio to the kernel-mode WDM system-wide mixer at 16-bit 44.1 kHz. 

• A Universal Disk Format (UDF) DVD file reader, splitter, and navigator that provides access for DirectShow clients to separate video and audio streams. 

WDM Streaming Class Driver

Windows 98 contains support for technologies that require data to be moved in real time. Digital audio, video, and scanner/camera support may contain data streams that can overwhelm the PCI bus. The Streaming Class Driver (file name Stream.sys) was written to address this issue.

How WDM Streaming Works

WDM Streaming is directly based on the DirectShow model of user mode filters. In the context of WDM Streaming, a filter represents a kernel-mode driver. The Streaming Class Driver takes the API calls that normally communicate back and forth from the user level (ring 3) to the kernel level (ring 0) and pushes them down so they occur mostly at the kernel level. This allows data streams to be passed through the operating system and to move at a faster pace, because CPU cycles are not used to pass the information back and forth between the user mode and kernel levels.

Efficient Streaming

Typically, time-sensitive applications are divided into several tasks.

Figure 12.1 shows the typical path that a data stream follows. The data stream (for instance, an MPEG-2 data stream with audio) is passed to the first filter to decompress the video stream. Then the entire stream is handed back to the device driver in kernel mode. When the audio portion of the data stream needs to be decoded, the entire data stream is passed back up to the user level. These transitions are CPU-intensive and are not the most efficient way to pass the data stream, because each transition carries the extra load to switch between the two levels, and the data may have to go through various validation stages.

Figure 12.1 Typical data stream path in a non-WDM case 

WDM Streaming enables more efficient data streaming, as shown in Figure 12.2. In this example, almost all data streaming takes place in kernel mode. The filter modules executing in user mode apply controls only to the kernel-mode device drivers/hardware. For example, in the case of an audio data stream, a user-mode filter can apply a loudness control to the kernel-mode driver/hardware renderer.

Note Kernel streaming (KS) filters are not necessarily bound to any piece of hardware.

 

Figure 12.2 WDM data stream path 

Additionally, a stream may be produced and consumed entirely in kernel mode, with only mechanisms exposed to the user-mode client, as shown in Figure 12.3. In this case, a source filter reading a file, for example, or picking up data off a 1394 bus passes it through some hardware-based codec and on through the remaining filters. If the filters in between reside on the same physical hardware, they may negotiate a faster transfer mechanism, or interface, which avoids memory copies and may avoid use of the host CPU in their communication.

 

Figure 12.3 Data stream produced and consumed in kernel mode 

DVD

DVD places full-length motion pictures on digital disc-sized media. DVD hardware and software are specifically tailored to read multiple digitally stored data streams concurrently. DVD is not computer-only media; many DVD players (which are similar to laser disc players) on the market are designed to feed the images directly to a television. DVD has two major compression technologies, MPEG-2 and Dolby Digital (sometimes referred to as AC-3), which are used to store video and audio on a disc. This allows more than two hours of better-than-laser-disc video and better-than-CD audio to be stored on a single disc, opening up new possibilities for content providers. Such possibilities include the ability to have different screen formats (for instance, letterbox, pan and scan, and so on), different soundtracks, different languages, and different ratings (such as both R and PG versions of a movie) all on the same disc.

Hardware Requirements for DVD

DVD requires a special drive as well as a decoder (a hardware decoder card, a software decoder, or a combination of the two). DVD drives use a laser with a shorter wavelength than that used on standard CD-ROM drives, which allows it to read data stored in smaller areas on the media. Standard CD-ROM drives cannot read DVD discs. However, DVD drives can read standard CD-ROM data and audio CDs.

Full-motion video is stored on DVD in the MPEG-2 format. Because high rates of transfer are necessary to read and display full-screen, real-time data, most of the decoding is done at the hardware level, so your DVD system must have a decoder.

Capacity 

The current capacity of a DVD disc starts at 4.7 billion bytes. Vendors have developed technology to make both sides of the media readable and to layer data on each side (for example, a gold layer of data can be placed above a silver layer). Lower laser power is used to read the top layer, and increased laser power allows the bottom layer to be read. Combining these two options increases the total possible capacity of a single DVD disc to 17 billion bytes.

Uses 

A DVD drive has many uses. Although it was specifically designed to handle the challenges that come with displaying full-motion video, its massive storage capacity allows it to perform in other ways, including the following:

• Support for DVD movie playback is especially important for Entertainment computers, but is also important for any multimedia hardware platform used to provide support for playback of movies. This support includes the full range of interactivity and quality playback found on a standard DVD video player. Because computers can achieve greater image quality than can television sets, a DVD disc on a computer running Windows 98 achieves even better quality than what is available on standard DVD video player devices.

• DVD discs and devices provide cost-effective storage for large data files. In the future, DVD will allow for writable devices, opening a larger range of options. 

DVD Software Components

DVD technology includes several software components: MPEG-2, AC-3 (audio streaming), Subpicture, two class drivers (a ROM class driver and WDM), UDF file system, DirectShow, DirectDraw, and a copyright-protection encryption key.

MPEG-2 

MPEG-2 is a type of video compression that saves space by saving only the data that changes on the screen. So rather than storing a 640 x 480 x 12 (12-bit color depth) for each frame, only those pixels that change are encoded.

Dolby Digital (AC-3) 

AC-3 is a type of audio stream developed by Dolby Labs. It allows up to five separate audio channels (left and right front, left and right rear, and center) and a subwoofer channel.

Subpicture 

DVD discs contain a third data stream called Subpicture. The Subpicture stream delivers the subtitles and any other movie add-on data, such as director's comments, that can be displayed while playing the movie.

DVD-ROM Class Driver 

DVD-ROM drives use a specific command set referred to as the Mt. Fuji specification. The Windows 98 implementation of this command set is provided using the class driver/minidriver architecture conforming to WDM. A class driver is used to provide support for the full Mt. Fuji specification, while the manufacturer of the DVD drive provides a device-specific minidriver that handles device-specific functions. This allows both Windows 98 and Windows NT version 5.0 to read DVD disc data sectors.

WDM Streaming Class Driver

Issues with playing a full-length movie include the fact that data is moved in a different way. Data is usually thought of as being read from the media, loaded into memory, and then used. With multimedia applications, the process is slightly different. Because a full-length movie requires that a large amount of data be moved while playing the movie—the data must be read sequentially, displayed, and cleared by the time the next frame is ready to be displayed. The Streaming Class driver was introduced to address this real-time need. For more information about this driver, see "WDM Streaming Class Driver" earlier in this chapter as well as Chapter 30, "Hardware Management."

UDF file system 

Data on a DVD disc is stored using a file system called Universal Disc Format (UDF). Support for this file system is implemented using installable file system architecture of Windows 98.

DirectShow 

DirectShow (formerly known as ActiveMovie) provides support for a DVD Navigator/Splitter, proxy filters for video and audio streams, a video mixer, a video renderer, and an audio renderer. DVD movies have the equivalent of channels for the various data streams necessary for a full-length movie. Data streams consist of not only the MPEG portion but also digital audio, which may have Dolby surround sound and close captioning information. For a single video image, DVD can provide up to 8 languages/sound tracks and 32 subtitle tracks, and supports up to 9 angles and 8 ratings. DirectShow 2.0 provides support for keeping track of these various data streams and passing them to the proper codec.

DirectDraw HAL with VPE 

Decoded video can become quite large. An MPEG-2 stream starts out at a rate of around 5–10 megabits per second (Mbps). After the stream is decoded, it can easily exceed 100 Mbps. The processing of this amount of information in a continuous stream could overwhelm the PCI bus. So most of the decoding of the information has been moved back to the hardware level by using dedicated MPEG decoder cards. Support for these decoder cards is built in to DirectX 5.0, with DirectDraw's support for Video Port Extensions (VPEs). Video Port Extensions allow the MPEG stream to be written directly to the frame buffer memory of the Video Card from the MPEG decoder card. Data transfer occurs through a special cable that connects the video card and the decoder card at the hardware level. DirectDraw 5.0 allows the data stream to be moved through the hardware layer while keeping track of such things as synchronization.

Copyright Protection 

Copyright protection for DVD is provided by encrypting key sectors on a disc and then decrypting those sectors before decoding them. Microsoft provides support for both software and hardware decrypters using a software module that enables authentication between the decoders and the DVD-ROM drives in a computer.

As part of the Copyright Protection scheme used for DVD, the DVD Consortium has set up six worldwide regions. Discs are playable on DVD devices in some or all of the regions according to regional codes set by the creators of the content. Microsoft provides software that responds to the regionalization codes as required by the DVD Consortium and as part of the decryption licenses.

DVD in Windows 98

DVD hardware and software requirements are described in the following sections.

Hardware 

A DVD-ready system must meet the specifications listed in the PC 97 Hardware Design Guide. These requirements are described in Table 12.3.

Table 12.3 DVD hardware requirements 

Hardware	Required	Recommended
Processor	P120 (or equivalent) with 256-KB cache	P166 (or equivalent) with 256-KB cache; MMX enabled
RAM	16 MB	32 MB
Graphics display	800 x 600 x 16 bpp with Video Port Extensions (VPEs)	1024 x 786 x 16 bpp; 2-D accelerator
Decoder	Supported Decoder Card	Supported Decoder Card; NTSC / PAL TV Output

The following decoder cards and DVD drives are directly supported in Windows 98:

• Toshiba, Toshiba Infinia 

• Quadrant, Dell XPS series 

• Luxsonor, Creative PC-DVD (not Dxr2 and prior) 

Software 

Windows 98 ships with a DVD player named Dvdplay.exe. Dvdplay.exe is a stand-alone executable and has no program-specific DLLs associated with it. Like most applets shipped with Windows, DVDPlay has only basic functionality and may be replaced by a third-party application. If you have a supported decoder, DVD Player can be installed and uninstalled from the Control Panel using the Add/Remove Programs option.

Note When the DVD Player is launched, it searches all local drives in alphabetical order, starting with C, looking for a folder called Video_TS. When this folder is located, the data file within it is loaded, and video streaming begins. If this folder exists on a drive that comes before the DVD drive, the player will try to play the data in the first folder it finds. This is also an issue with systems that have multiple DVD drives.

The basic DVD program is shown in Figure 12.4. It contains, from left to right, buttons for choosing a channel; VCR style controls for controlling playback; and menu navigation buttons for using the on-screen menu choices.

Figure 12.4 Basic DVD player 

Recording, Editing, and Playing Audio

Windows 98 multimedia services provide extensible, device-independent audio support. Windows 98 features services for sound control for computers that have sound cards and for waveform-audio, MIDI, and mixer devices.

With audio support in Windows 98, users can do the following:

• Use Media Player or ActiveMovie Control to play WAV or MIDI files. 

• Use applications that take advantage of DirectSound audio acceleration. 

• Use the Sound option in Control Panel to assign sound clips to play each time a specific event occurs. 

• Use CD Player to play audio CDs. 

• Use Sound Recorder to record sound. 

• Use built-in Windows 98 OLE support to copy or link audio clips in other documents. For more information, see Chapter 25, "Application Support." 

For more information about recording, editing, and playing multimedia files, see Help.

Windows 98 Support for MIDI

Musical Instrument Digital Interface (MIDI) is a serial interface standard that allows for the connection of music synthesizers, musical instruments, and computers. The MIDI standard is based partly on hardware and partly on a description of the way in which music and sounds are encoded and communicated between MIDI devices.

MIDI is used as a development tool for musicians. Virtually all advanced music equipment supports MIDI, and MIDI offers a convenient way to control the equipment precisely. MIDI is the electronic equivalent of sheet music. For example, if you buy a CD that contains a particular performance of a piece of music, the data on the CD requires no interpretation at all — it is straightforward playback. If you buy the sheet music and have someone play it, it requires very little data, but, depending on the quality of the instruments, the hardware, and the software, you can get a good or a bad interpretation of that piece of music.

Windows 98 supports the General MIDI Specification to request particular instruments and sounds. This specification is an industry standard that defines how MIDI should be used, and it is supported by Microsoft and most MIDI sound card manufacturers.

Windows 98 supports MIDI streams. This technology is used in advanced sound cards to play very complex MIDI sequences with less CPU use. This technology allows Windows 98 to receive requests for multiple MIDI instructions at once and process the instructions in the operating system. As a result, playing MIDI files now requires even less computing power than before, and it allows developers to process MIDI instructions, graphics, and other data even more successfully.

MIDI devices supported by Windows 98 include the following:

• FM Synthesis 

• Hardware Wavetable Synthesis 

• Software Wavetable Synthesis 

• MPU401 

For more information about playing a MIDI sound file and installing a sound card, see Help.

Recording Sound

If you have a microphone connected to your computer, you can record sound by using Sound Recorder. 

When using Sound Recorder, you can use a real-time audio compression filter to reduce the amount of disk space required to store audio. For example, to turn on voice compression when recording so the file is compressed in real-time, use the GSM 6.10 format in the Convert Now dialog box in Properties from the File menu.

To enable real-time compression while recording

1. On the Start menu, point to Programs, point to Accessories, point to Entertainment, and then click Sound Recorder. 

2. Click the File menu, and then click Properties. 

3. From the drop down box, choose Recording formats. 

4. Click Convert Now, choose a compression format, and then click OK. 

5. Click OK to start recording. 

For more information about recording sound with a microphone, see Help.

Controlling Audio Input Levels

Windows 98 includes a Volume Control tool that provides audio line routing services to manage the different audio lines installed on a computer. An audio line consists of one or more channels of waveform-audio data coming from one origin or system resource. For example, a stereo audio line has two data channels, yet it is considered a single audio line. A mixer control can take on many different characteristics (such as controlling volume), depending on the characteristics of the associated audio line.

The number of lines users can mix by using Volume Control depends on the number of audio source lines the computer has and whether they are using Volume Control for input or output.

For more information about mixing sounds, see Help.

Recording and Playing Digital Video

Windows 98 video services provide the resources for capturing video clips, compressing the content, and controlling playback.

Displaying digital video involves moving and processing huge streams of data continuously and efficiently. In earlier versions of Windows, the process of displaying digital video relied on a series of 16-bit systems — from reading data from the disk, to decompressing the video data, to displaying it on the screen. With the Windows 98 32-bit architecture, users can display bigger, smoother, and more colorful digital video, without adding any hardware.

Windows 98 multimedia is fully compatible with 16-bit multimedia titles. Testing has shown that the 32-bit improvements in file access speed and stream handling result in performance gains for 16-bit multimedia applications and especially for the new generation of 32-bit applications developed for Windows 98.

To determine the format in which an existing video clip was authored

• Right-click the icon for the digital-video file, click Properties, and then click the Details tab. 

For more information about playing video clips, see Help.

Buying a Multimedia Computer

Make sure to select a balanced computer, in which all components work together to meet the demands of supporting multimedia applications. In multimedia systems, balance is more important than speed, because multimedia playback places heavy demands on the CD-ROM (for reading data), on the hard disk (for writing data), on the CPU (for decompressing data), and on the video and audio subsystems (for playback). A fast CPU alone does not guarantee a great playback system.

The PC 97 Hardware Design Guide introduced the Entertainment PC as a distinct category of Windows-based computer, differentiated from the Basic PC by its ease of use and the breadth and quality of its multimedia capabilities. For example, the graphics, video, and audio subsystems for Entertainment PCs are designed to optimize the capabilities of software that uses Microsoft DirectX interfaces.

An Entertainment PC 98 system is optimized for the following uses:

• Games, including the best titles, with the most complex, realistic graphics and audio. 

• Education, using the most engaging titles, with full-screen video, interactive animation, and so on. 

• Active Internet, providing enhanced Web communications capabilities, with personalized and animated Web sites, chat rooms, and so on. 

• Personal communications through multimedia e-mail, Internet audio phone, video phone, and so on. 

• Interactive, high-resolution television and movie viewing through higher video quality, real-time links to content producers, and so on. 

• Connection with traditional consumer-electronics devices, providing home theater surround audio such as Dolby Digital (AC-3) for games and DVD movies, and fast and easy capture, editing, and playback of personal video. 

The following sections provide guidelines for what to look for in a multimedia system, along with specifics for audio components, MIDI components, and video components.

What to Look for in Basic Computing Power

This section presents a summary of general system recommendations for a multimedia computer, including system board, memory, and BIOS. The minimum PC 98 performance recommendations consist of the following:

• 200-MHz Pentium processor with Intel MMX technology, or equivalent. The minimum microprocessor capability is specified to support the demands of rich media, Internet access, and conferencing. 

• Minimum 256-KB Level 2 (L2) cache or equivalent. 

• 32-MB minimum system memory. Recommended: 64 MB. Memory should be 66-MHz Dynamic Random Access Memory (DRAM) or better. 

• Graphics adapter using PCI, AGP, or other high-speed bus. 

• Adapter support for screen resolutions as defined by VESA up to the PC 98 required maximum, including 640 x 480 x [8, 15, 16, 24] bpp, 800 x 600 x [8, 15, 16, 24] bpp, and 1024 x 768 x [8, 15, 16] bpp. 

• Two USB ports to support connection of auxiliary input devices, such as game pads, joysticks, and track balls. 

• Two IEEE 1394 ports to support camcorders and other digital consumer electronics devices. 

• Keyboards, pointing devices, and game pads and their connections compliant with the USB Device Class Definition for Human Interface Devices, Version 1.0 or higher, and with the USB HID Usages Table, whether implemented as wired or wireless devices. 

• Data/fax/voice modem that supports V.pcm. 

What to Look for in Audio Hardware

Audio for a multimedia computer should meet PC 98 audio requirements, which include requirements for audio hardware capabilities, performance metrics, and external connections. The following are some key features to look for when you want to purchase a multimedia computer with high-quality audio :

• A sound card with a 16-bit digital-to-analog converter (DAC) for playback and a 16-bit analog-to-digital converter (ADC) for recording (necessary for applications developers). 

• Full-duplex support to record and play sounds at the same time. The device should be capable of capturing audio at one sample rate while playing audio at another sample rate. 

• Full-duplex audio capability for audio hardware supporting H.323/H.324 video and audio conferencing. 

• Audio hardware supporting CD-ROM and DVD media playback, made possible by built-in or external audio codec support for playback of 16-bit stereo PCM data at both a 44.1-kHz and 48-kHz sample rate.

• Audio hardware featuring the acceleration supporting 3-D games, made possible by built-in or external audio codec support for playback of 16-bit stereo PCM data at a 44.1-kHz sample rate. 

• CD-ROM drive providing 12x or higher performance. The CD-ROM drive must support 1200 KB per second average throughput or higher performance when running in the fully on power state. 

  Audio system providing support for basic data formats. The audio system must provide full-duplex support of the following audio formats:

  • Mono/stereo 

  • 8-bit unsigned 

  • 16-bit signed 

• Audio system support for both recording and playing back of sample rates that include 8, 11.025, 16, 22.05, 44.1, and 48 kHz waveforms. Compact disc–quality sound uses 44 kHz. The 11 kHz and 22 kHz waveforms are fractions of 44 and are often used for compressed waveforms that are meant to save CPU processing. The 8 kHz waveform is used for compatibility with telephone audio, and 16 kHz waveform is used for speech recognition. 

  Audio system with sufficient externally accessible inputs and outputs. At a minimum, the audio system must have the following features:

  • A monaural microphone, stereo line input, or both 

  • Stereo line-level output 

• Audio system support of full-duplex operation at independent sampling rates. Voice recognition and audio/video conferencing require the audio system to play back and record simultaneously. Incoming and outgoing audio should be capable of operating at independent sampling rates. This recommendation considers the entire system, including the possibility of USB speakers or microphones. 

• Audio system providing hardware or software support for the Downloadable Samples (DLS) specification. Support for DLS as defined by the MIDI Manufacturers Association is recommended. For more information, see DLS Specification, version 1.0 or higher, at https://www.midi.org/ . 

For computers that support software or hardware decoding and playback of DVD-Video or MPEG-2 video, the audio decoder must be capable of supporting the following formats:

• MPEG-1 Layer 2 stereo, at 44.1 and 48 kHz less than or equal to 384 Kbps. 

• Linear PCM (LPCM) less than or equal to 8 channels, 16-bit, 20-bit, and 24-bit at 48 or 96 kHz less than or equal to 6.144 Mb/s. 

Note Conversion to 48-kHz 16-bit stereo is acceptable when the content exceeds the available resolution, sampling rates, or number of output channels.

What to Look for in MIDI Support

Microsoft recommends that sound cards for both consumer and developer systems include the following:

• General MIDI support. General MIDI refers to a system of assigning numbers to each kind of instrument, so that, for example, instrument 12 on one computer is the same as instrument 12 on all others. 

• Support for polyphony, the ability to play multiple sounds at the same time. Systems should include at least 32-voice polyphony. Support for more concurrent sounds means a fuller sounding playback. 

• Wave table sound rather than FM synthesis.

• Standard MIDI port. This is normally implemented as an MPU-401 port. If you play a MIDI stream to the MPU-401 port, you will not hear anything unless you have a MIDI playback device attached to the port. You can use this port to plug in MIDI devices such as piano-style keyboards; it also supports joysticks.

  Note An external MIDI port is needed only if you have external MIDI equipment to connect to the computer. 

• System audio hardware acceleration features, such as Downloadable Samples (DLS) wave-table MIDI synthesis and multistream Head Related Transfer Function (HRTF) 3-D.

• Hardware for higher quality or concurrency DLS wave-table MIDI synthesis, with associated mixing and SRC support. A wave table card should send the audio to the same speakers as their wave output. 

What to Look for in Video and Broadcast Support

Video and broadcast television are becoming integral elements of computer usage, especially for an Entertainment PC. For Entertainment PC 98, important design issues include the following:

• Increased quality of video capture and playback. This includes increased image resolution and increased frame rates. 

• Low-latency video delivery, displaying video from both internal and external video devices. 

• Implementation of a graphics adapter video port for use by one or more video sources. 

The Entertainment PC 98 hardware recommendations for video capture, television output, and DVD playback support include the following:

• DVD-Video support with MPEG-2 hardware. 

• WDM support implemented for all video input and capture capabilities. 

• Support for National Television System Committee (NTSC), Phase Alternation by Line (PAL), or both types of television output, except for systems bundled with a large-screen super VGA (SVGA) monitor. 

• Super VGA resolution. At a minimum, the consumer system should have a Super VGA display, which provides at least 800 x 600-pixel resolution with approximately 64,000 colors (16 bpp) for users working with complicated graphics.

• Hardware-assisted DirectDraw acceleration, Direct3D acceleration, and video playback. 

Troubleshooting Multimedia

This section describes how to identify and resolve multimedia software problems.

For information about troubleshooting related hardware problems, see Chapter 24, "Device Management."

For information about general troubleshooting issues, see Chapter 27, "General Troubleshooting."

Correcting Problems with Playing WAV Files

When a multimedia application is unable to play waveform-audio (WAV) files, it is usually caused by one or more of the following problems.

The sound card is not installed properly. 

Most sound cards come with MS-DOS- based programs for playing sounds or testing card configurations. Run these programs in MS-DOS mode; if the sound card does not work with these programs, it will not work with Windows 98 sound support.

Make sure the sound card settings do not conflict with other hardware. Use the Add New Hardware icon in Control Panel to detect your hardware, thereby determining if you have any hardware for which the appropriate driver is not yet installed. Verify port and IRQ settings.

Note If the sound card can play MIDI files, the card is probably properly installed.

The volume is muted or too low. 

Check to see that the volume in Volume Control is not muted or too low.

To check the volume

• Click the Volume Control icon on the system tray, and make sure the Mute all check box for Wave is not enabled, or raise the volume slider for Wave if it is too low. 

  Note If the Volume Control icon is not on the system tray, click Start and point to Programs, Accessories, and Entertainment, and then click Volume Control. 

A waveform-audio driver is not installed. 

If you are running Sound Recorder and there is no waveform-audio driver installed, you will receive an error message. In this case, make sure that the waveform-audio driver is listed in the Multimedia devices list; you can see this list by clicking the Devices tab in the Multimedia option in Control Panel. Check with the manufacturer of the sound card to ensure you have the proper drivers. If you cannot find the correct driver for the sound card in the list, try using the Windows 95 driver for that card or connecting to the manufacturer's Web site and downloading a current driver.

You should also make sure the correct codec is installed. You can check the codec by clicking Multimedia in the Control Panel and then clicking the Devices tab. The codecs are listed under Audio Compression Codecs.

A waveform-audio MCI driver is not enabled. 

If you are running Media Player and cannot play WAV files, perform the following procedure to correct the problem.

To enable the waveform-audio MCI driver

1. In Control Panel, double-click Multimedia, and then click the Devices tab. 

2. In the Multimedia devices list, click the plus (+) sign next to Media Control Devices. 

   If Wave Audio Device (Media Control) does not appear in the list, the driver is not installed.

3. Click Wave Audio Device (Media Control), and then click Properties. 

4. In the Properties dialog box, click Use this Media Control device. 

Correcting Problems with Playing MIDI Files

A multimedia application's inability to play MIDI files is commonly caused by one or more of the following problems.

The sound card is not installed properly. 

Most sound cards come with MS-DOS- based programs for playing sounds or testing card configurations. Run these test programs; if the sound card does not work with these programs, it will not work with Windows 98 sound support.

Make sure that the sound card settings do not conflict with other hardware. Use the Add New Hardware option in Control Panel to detect your hardware, thereby determining whether you have any hardware for which the appropriate driver is not yet installed. Verify port and IRQ settings.

Note If the sound card can play WAV files, the card is probably properly installed.

The volume is muted or too low. 

Check to see that the volume in Volume Control is not muted or too low.

To check the volume

• Click the Volume Control icon on the system tray, and make sure the Mute all check box for MIDI is not enabled, or raise the volume slider for MIDI if it is too low. 

  Note If the Volume Control icon is not on the system tray, click Start and point to Programs, Accessories, and Entertainment, and then click Volume Control. 

A MIDI driver is not installed. 

If you are using Media Player and cannot play a MIDI file, it might be because there is no MIDI driver installed. Try installing the driver that came with the hardware. Or, if you do not find the correct driver for the sound card in the list, try using the Windows 95 driver for that card.

A MIDI MCI driver is not installed or enabled. 

In Media Player, make sure that the option named MIDI Sequencer appears in the Device menu. If not, the MIDI MCI driver is not installed or not enabled.

To verify that the MIDI MCI driver is enabled

1. In Control Panel, double-click Multimedia, and then click the Devices tab. 

2. In the Multimedia devices list, click the plus (+) sign next to Media Control Devices. 

   If MIDI Sequencer Device (Media Control) does not appear in the list, the driver is not installed. See the following procedure for instructions. 

3. Click MIDI Sequencer Device (Media Control), and then click Properties. 

4. In the Properties dialog box, click Use this Media Control device. 

To install the MIDI MCI driver

1. In Control Panel, double-click Add New Hardware, click No, I want to select the hardware from a list when prompted to have Windows 98 search for your hardware, and then click Next. 

2. In the Hardware Types list, click Sound, click Video And Game Controllers, and then click Next. 

3. Click Microsoft MCI in the Manufacturers list, and then click MIDI Sequencer Device (Media Control) in the Models list.

4. Click Next. 

5. To complete the installation, click Finish. 

The incorrect MIDI output device is selected.

If the selected midi device is incorrect, you hear no MIDI output. Choose only External MIDI or MIDI OUT for an add-on MIDI daughter card or if an external MIDI device (for example, a synthesizer) is connected to the MIDI port of a sound card.

For example, if you do not have an MPU-401 compatible synthesizer plugged into the MIDI port, make sure that MPU-401 is not selected as your default MIDI device.

To select the correct MIDI output device

1. In Control Panel, double-click Multimedia. 

2. Select the MIDI tab. 

3. Choose the proper MIDI playback device under MIDI output so that it appears in the box under Single Instrument. 

4. Click OK. 

Correcting Problems with Playing a DVD Disc

Because DVD uses several pieces, the first step in troubleshooting a DVD issue is to narrow down which piece is not functioning correctly.

• Make sure that the DVD drive is displayed as functioning correctly in Device Manager.

• Make sure that Windows 98 can read the data on the CD by using Windows Explorer to see the contents of the DVD disc. There can be at least two folders: Video_TS and Audio_TS. 

• Make sure that ActiveMovie is working correctly by playing an AVI file. 

Correcting Problems with Playing or Hearing an Audio CD

When a you are unable to hear an audio CD being played, it is commonly caused by one or more of the following problems.

The CD-ROM drive is not properly installed. 

Place a data CD in the CD-ROM drive, and make sure you can view the files in Windows Explorer or list the files at the command prompt. If you can, the CD-ROM drive is properly installed. If not, verify your disk drivers (ESDI, SCSI, Proprietary, MSCDEX), and make the appropriate configuration changes so that you can view the files on a data CD.

The volume is muted or too low. 

Check to see that the volume in Volume Control is not muted or too low.

To check the volume

• Click the Volume Control icon on the system tray, and make sure the Mute all check box for CD Audio is not enabled, or raise the volume slider for CD Audio if it is too low. 

  Note If the Volume Control icon is not on the system tray, click Start and point to Programs, Accessories, and Entertainment, and then click Volume Control. 

Digital CD audio for the CD-ROM device is not enabled. 

You can have Windows use digital playback of a CD audio for digital devices, such as USB speakers. This feature works with only certain CD-ROM devices.

To verify the digital CD audio is enabled

1. In Control Panel, double-click Multimedia, and then click the CD Music tab. 

2. Select the Enable digital CD audio for this CD-ROM device check box. 

The CD audio MCI driver is not installed. 

In Media Player, make sure that the option CD Audio appears in the Device menu. If not, the CD audio MCI driver is not installed or not enabled.

To verify the CD audio MCI driver is enabled

1. In Control Panel, double-click Multimedia, and then click the Devices tab. 

2. In the Multimedia devices list, click the plus (+) sign next to Media Control Devices. 

   If CD Audio Device (Media Control) does not appear in the list, the driver is not installed. See the following procedure for instructions. 

3. Click CD Audio Device (Media Control), and then click Properties. 

4. In the Properties dialog box, click Use this Media Control device. 

To install the CD audio MCI driver

1. In Control Panel, double-click Add New Hardware, click No, I want to select the hardware from a list when prompted to have Windows 98 search for your hardware, and then click Next. 

2. In the Hardware Types list, click Sound, click Video And Game Controllers, and then click Next. 

3. Click Microsoft MCI in the Manufacturers list, and then click CD Audio Device (Media Control) in the Models list.

4. Click Next. 

5. To complete the installation, click Finish. 

The CD-ROM is not connected to the sound card. 

If the CD-ROM is playing and there is no sound coming from the sound card speakers, try plugging the speakers or headphones into the audio jack on the face of the CD-ROM drive. If you get sound, check the internal or external audio connection between the CD-ROM drive and the sound card.

Correcting Problems with Hearing from Headphones

Verify that the sound card is correctly installed by reviewing the card's properties.

To view your sound card's properties

1. In Control Panel, double-click Multimedia, and then click the CD Music tab.

2. Make sure that the volume level is set to produce sound from the headphones. If not, use the slider to adjust the CD Music Volume. 

Note If you have Digital Playback enabled on the CD Music tab, the headphone output for the CD-ROM drive is disabled.

Additional Resources 

For more information about	See this resource
Multimedia in Windows 98	Microsoft Windows 98 Device Development Kit
Video support	https://www.microsoft.com/hwdev/platform/pcdesign/desguide/default.asp
Implementing drivers that support simultaneous use of devices	Microsoft DirectX Driver Development Kit
MIDI Manufacturers Association	https://www.midi.org/
Computer design guidelines	https://www.microsoft.com/hwdev/platform/pcdesign/desguide/default.asp