Editing Gravis UltraSound (section)

==GF1==
The GF1 was co-developed by Advanced Gravis and Forte Technologies (creator of the [[VFX1 Headgear]] [[virtual reality]] helmet) and produced by Integrated Circuit Systems under the ICS11614 moniker. The chip was derived from the [[Ensoniq]] [[Ensoniq ES-5506 OTTO|OTTO (ES5506)]] chip, a next-generation version of the music-synthesizer chip found in the [[Ensoniq VFX]] and its successors.

The GF1 is purely a sample-based synthesis chip with the [[polyphony]] of 32 [[oscillators]], so it can mix up to 32 mono [[Pulse-code modulation|PCM]] samples or 16 stereo samples entirely in hardware. The chip has no built-in codec, so the sounds must be downloaded to onboard [[RAM]] prior to playback. Sound [[data compression|compression]] [[algorithm]]s such as [[Interactive Multimedia Association|IMA]] [[ADPCM]] are not supported, so compressed samples must be decompressed prior to loading.

The sound quality of the GF1 is not constant and depends on the selected level of polyphony. A [[CD-quality]] 44.1&nbsp;kHz sample rate is maintainable with up to 14-voice polyphony; the sample rate progressively deteriorates until 19.2&nbsp;kHz at the maximum of 32-voice polyphony. The polyphony level is software-programmable, so the programmer can choose the appropriate value to best match the application. Advanced sound effects such as [[reverberation]] and [[Chorus effect|chorus]] are not supported in hardware. However, software simulation is possible; a basic "echo" effect can be simulated with additional tracks, and some [[tracker (music software)|tracker]]s can program effects using additional hardware voices as accumulators.

===Sample RAM===
The UltraSound offers MIDI playback by loading instrument patches into adapter RAM located on the card, not unlike how instruments are stored in [[Read-only memory|ROM]] on other sample-based cards (marketed as "wavetable" cards). The card comes with a 5.6 MB set of instrument patch (*.PAT) files; most patches are sampled at 16-bit resolution and [[Loop (music)|looped]] to save space. The patch files can be continuously tweaked and updated in each software release.

The card's various support programs use .INI files to describe what patches should be loaded for each program change event. This architecture allowed Gravis to incorporate a General MIDI-compatible mapping scheme. [[Windows 95]] and [[Windows 98|98]] drivers use UltraSound.INI to load the patch files on demand. In [[DOS]], the loading of the patches can be handled by ''UltraMID'', a [[middleware]] [[Terminate-and-stay-resident program|TSR]] system provided by Gravis that removes the need to handle the hardware directly.  Programmers are free to include the static version of the UltraMID library in their applications, eliminating the need for the TSR. The application programmer can choose to preload all patches from disk, resizing as necessary to fit into the UltraSound's on-board RAM, or have the middleware track the patch change events and dynamically load them on demand.  This latter strategy, while providing better sound quality, introduces a noticeable delay when loading patches, so most applications just preload a predefined set.

Each application can have its own UltraMID.INI containing a set of patch substitutions for every possible amount of sample RAM (256/512/768/1024 kB), so that similar instruments are used when there is not enough RAM to hold all of the patches needed (even after resampling to smaller sizes). Unused instruments are never loaded. This concept is similar to the handling of sample banks in [[Sampler (musical instrument)|digital samplers]]. Some games — including ''[[Doom (1993 video game)|Doom]]'', ''[[Doom II]]'' and ''[[Duke Nukem 3D]]'' — come with their own optimized UltraMID.INI.

The UltraSound cards gained great popularity in the PC tracker music community. The tracker format was originally developed on the [[Commodore International|Commodore]] [[Amiga]] personal computer in 1987, but due to the PC becoming more capable of producing high-quality graphics and sound, the demoscene spilled out onto the platform in droves and took the tracker format with it. Typical tracker formats of the era included [[MOD (file format)|MOD]], [[S3M]], and later [[XM (mod format)|XM]]. The format stores the notes and instruments digitally in the file instead of relying on a sound card to reproduce the instruments. A tracker [[module file|module]], when saved to disk, typically incorporates all the sequencing data and samples, and typically the composer would incorporate their assumed name into the list of samples. This primitive precursor to the modern sampler opened the way for Gravis to enter the market, because the requirements matched the capabilities of the GF1 chip ideally. The problem with other sound cards playing these formats was that they had to [[downmixing|downmix]] voices into one or both of its output channels in software, further deteriorating the quality of 8-bit samples in the process. An UltraSound card was able to download the samples to its RAM and mix them using fast and high-quality hardware implementation, offloading the CPU from the task. Gravis realized early on that the demo scene support could be a sales booster, and they gave away 6000 cards for free{{Citation needed|date=September 2011}} to the most famous scene groups and people in the scene.

{{See also|Tracker (music software)|l1=Tracker}}

===Compatibility===
As the GF1 chip does not contain AdLib-compatible [[OPL2]] circuitry or a codec chip, [[Sound Blaster]] compatibility was difficult to achieve at best. Consumers were expected to use the included emulation software to emulate other standards, an activity not necessary with many other cards that emulated the Sound Blaster through their sound hardware. The emulation software ran as a huge TSR that was difficult to manage in the pre-Windows days of complicated [[DOS extender]]s.

Although there was native support for many popular games that used middleware sound libraries like HMI (Human Machine Interfaces) Sound Operating System, the Miles Audio Interface Libraries (AIL), the [[Miles Sound System]] or others, the user had to patch the games by replacing the existing sound drivers with the UltraSound versions provided on the installation CD. Also, the UltraSound required two [[Direct memory access|DMA]] channels for [[full-duplex]] operation, and 16-bit channels were generally faster, so many users chose to use them, but this led to errors for games that used the [[DOS/4GW]] DOS extender, which was common in the UltraSound's era.

The two principal software sound emulators included with software package were:
*''SBOS'', Sound Board OS — Sound Blaster Pro 8-bit stereo emulation and AdLib FM synthesis. It was a real-mode software emulator that recreated the AdLib's OPL2 FM synth chip and required that the user have a [[Intel 80286|286]] processor or better. There were special versions for the UltraSound MAX (MAXSBOS) and AMD InterWave-based cards (IWSBOS), which made use of the CS4231 codec chip instead.
*''Mega-Em'' — advanced emulation software that required at least a [[Intel 80386|386]] processor and [[Expanded Memory|EMM]] manager with [[DOS Protected Mode Interface|DPMI]]/[[VCPI]] support. Mega-Em emulated the 8-bit Sound Blaster circuitry for sound effects and the [[Roland MT-32]]/[[Roland LAPC-I|LAPC-I]] or [[Roland Sound Canvas]]/[[MPU-401]] for music. It supported UltraMID TSR functionality.