Subject: SGI audio Frequently Asked Questions (FAQ) Newsgroups: comp.sys.sgi.misc,comp.answers,news.answers From: sgi-faq@viz.tamu.edu (The SGI FAQ group) Date: 20 Nov 1994 07:00:00 GMT Archive-name: sgi/faq/audio Last-modified: Tue Nov 15 14:55:30 CST 1994 SGI audio Frequently Asked Questions (FAQ) This is one of the Silicon Graphics FAQ series, which consists of: SGI admin FAQ - IRIX system administration SGI apps FAQ - Applications and miscellaneous programming SGI audio FAQ - Audio applications and programming SGI graphics FAQ - Graphics and user environment customization SGI hardware FAQ - Hardware SGI Impressario FAQ - IRIS Impressario SGI Inventor FAQ - IRIS Inventor SGI misc FAQ - Introduction & miscellaneous information SGI movie FAQ - Movies SGI Performer FAQ - IRIS Performer SGI pointer FAQ - Pointer to the other FAQs Read the misc FAQ for information about the FAQs themselves. 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The contents are accurate as far as we know, but the usual disclaimers apply. Please send additions and changes to sgi-faq@viz.tamu.edu. Topics covered in this FAQ: --------------------------- -1- How do I program the Motorola 56000 DSP on the Indigo (R3K and R4K)? -2- How do I connect my stereo to my Ind{igo,igo2,y}? -3- How do I change the volume of the audio out the back of my machine? -4- Indigo2 speaker seems quieter than my Indigo. Am I imagining things? -5- I need to crank up the input gain on Indigo2 to use the microphone successfully. What's the scoop? -6- The glossy paper says that Indigo2 and Indy have 4-channel input and output. That sounds really cool. How do I use it? -7- Okay, so 4-channels of input and output is great, but I need more. Can I get more channels of audio for my machine? -8- Now that I have IRIX 5.X, I can't seem to find audio.h and libaudio.a in order to compile my audio code. What gives? -9- I like the boot tune, but it's just a bit too loud. How do I tone it down a bit? -10- How can I change the output speaker/headphone volume from a shell script? -11- What 3rd party audio solutions exist for Silicon Graphics machines? -12- I'd like to write my own audio programs. How do I get started? ---------------------------------------------------------------------- Subject: -1- How do I program the Motorola 56000 DSP on the Indigo (R3K and R4K)? Date: 20 Aug 94 00:00:01 EST Short answer: You don't. Long answer: The DSP on the Indigo is used exclusively by the audio system: whenever you are using the audio, you are using the DSP. In order to insure that audio processes are serviced, access to the DSP is limited to the audio device driver which performs all functions on behalf of application programs. Moreover, any code developed for the DSP on the Indigo may not work on other systems since the DSP is not guaranteed to be present. For instance, Indigo2 and Indy do not have a DSP. Audio is supported by a combination of code running on the CPU and a audio ASIC chip. SGI supports the Audio Library software inter- face as opposed to any particular hardware implementation of the audio system. Lastly, any signal processing code developed on the host CPU benefits from speed increases of the CPU (and this code is easier to write as well). ------------------------------ Subject: -2- How do I connect my stereo to my Ind{igo,igo2,y}? Date: 20 Aug 94 00:00:01 EST The Line in and Line out levels have been designed to be directly connected to conventional stereo systems. One way to do it is to connect it up as if the computer was a tape recorder. Line out on the computer connects to Rec in on the stereo and Line in connects to Rec out. ------------------------------ Subject: -3- How do I change the volume of the audio out the back of my machine? Date: 20 Aug 94 00:00:01 EST The headphone and speaker volume is adjusted using apanel(1). The sliders under the 'Speaker' label control the output volume of the speaker and headphone. The line-level output voltage is not affected. ------------------------------ Subject: -4- Indigo2 speaker seems quieter than my Indigo. Am I imagining things? Date: 20 Aug 94 00:00:01 EST No, this is not a figment of the imagination. There are two factors at work that make the Indigo2 quieter than Indigo: 1) the speaker amp is less powerful on Indigo2; 2) the system fan on Indigo2 is louder than the Indigo fan. These two things lead to a quiet speaker that seems even quieter. See the release notes for more information. ------------------------------ Subject: -5- I need to crank up the input gain on Indigo2 to use the microphone successfully. What's the scoop? Date: 20 Aug 94 00:00:01 EST The Indigo2 and Indy both have less input gain than the Indigo and 4D/35. However, all have plenty of gain to operate the microphone. On the Indigo2 and Indy, you have to set the input gain to a larger nominal level. ------------------------------ Subject: -6- The glossy paper says that Indigo2 and Indy have 4- channel input and output. That sounds really cool. How do I use it? Date: 20 Aug 94 00:00:01 EST In order to enable 4-channel audio, you must choose "4-channel mode" from the 'Options' menu of apanel or make a call in your program to ALsetparams(3A). See the man page for ALsetparams(3A) for more infor- mation. Enabling the 4-channel mode will cause the electrical char- acteristics of your audio connections to change: the headphone jack will become a second line-level output (like the normal line-level output). The mic input will become a second line-level input *if* you have 'line' selected as your input source. If you have the input source set to 'mic', then the mic input will continue to behave as a microphone input. Lastly, when your machine is in 4-channel mode, the input and output sample rates will be locked together. Thus, changing the input or output rate in this mode will affect the output or input rate, respectively. You may also run 4-channel applications when the audio system in in 2-channel mode, and vice versa (2-channel applications work when the system is in 4-channel mode). ------------------------------ Subject: -7- Okay, so 4-channels of input and output is great, but I need more. Can I get more channels of audio for my machine? Date: 20 Aug 94 00:00:01 EST Sonic Solutions (San Raphael, CA) has announced that it is porting Sonic System to SGI platforms. See below. ------------------------------ Subject: -8- Now that I have IRIX 5.X, I can't seem to find audio.h and libaudio.a in order to compile my audio code. What gives? Date: 20 Aug 94 00:00:01 EST The #include file audio.h and the library libaudio.a became a part of the "Digital Media Developement Option" (dmdev) in IRIX 5.X. Dmdev contains more than just the audio development libraries, and it is available for an extra fee. If you are like many people and think this is a bogus situation, tell your salesperson. ------------------------------ Subject: -9- I like the boot tune, but it's just a bit too loud. How do I tone it down a bit? Date: 20 Aug 94 00:00:01 EST The boot tune volume is controlled by the 'volume' variable used by the system PROM. The value for 'volume' can be set in the range [0-255], where lower numbers represent a lower boot tune volume. A 'volume' value of 0 disables the boot tune, viz. the tune is not played at all. The value of 'volume' can be set in the PROM monitor or using the nvram(1M) command. ------------------------------ Subject: -10- How can I change the output speaker/headphone volume from a shell script? Date: 20 Aug 94 00:00:01 EST You can use two methods to do this: 1) apanel -nodisplay or volume.c program (this program can be found in ~4Dgifts/examples/ libaudio directory). ------------------------------ Subject: -11- What 3rd party audio solutions exist for Silicon Graphics machines? Date: 20 Aug 94 00:00:01 EST Doug Cook maintains a list of "Audio Applications for Silicon Graphics Systems" which he posts to comp.sys.sgi.audio. A copy is at viz.tamu.edu:/pub/sgi/lists/audio-apps. ------------------------------ Subject: -12- I'd like to write my own audio programs. How do I get started? Date: 20 Aug 94 00:00:01 EST First, for 5.2 systems you need the Digital Media Development Option. From Michael Portuesi (portuesi@sgi.com): The Digital Media Development Option contains the Video, Audio, Audio File, MIDI, CD, DAT, Movie, and Compression Libraries for your digital media programming enjoyment. The part number for the Digital Media Development Option is SC4-DMDEV-2.0. If you would like to develop applications which manipulate QuickTime files, you must also order the companion product, QuickTime 1.0 Compressor Library, part number SC4-QTCL-1.0. In the United States, you can order these products by calling Silicon Graphics toll-free at 1-800-800-SGI1 (1-800-800-7441). If you live in a country other than the United States, contact your nearest Silicon Graphics office, or call one of these regional telephone numbers: Europe (41) 22-798.75.25 (Geneva, CH) North Pacific (81) 3-5420.71.10 South Pacific (61) 2-879.95.00 Latin America 1(415) 390.46.37 Canada 1(416) 625-4747 For audio, example code is contained in ~4Dgifts/examples/libaudio. This example code comes with the DMDEV option. Other code demonstrating the use of the CD and DAT audio libraries can be found in a 'tar' file at ftp.sgi.com:~ftp/sgi/dat. ------------------------------ End of sgi/faq/audio Digest ****************************** -- The SGI FAQ group sgi-faq@viz.tamu.edu Finger us for info on the SGI FAQs, or look in viz.tamu.edu:/pub/sgi.