On Wed, 03 May, 2006 at 03:37AM -0400, [EMAIL PROTECTED] spake thus: > > I have gained much valuable insight from reading the posts from last month on > Linux Audio Dev and OpenGraphics. I have tried to incorporate what wisdom I > could. Someone wiser than I could greatly improve on this, of course. Hence > this document.
When can you send me one? I'm excited and I don't like waiting! :) This all sounds very very good. > > Low to mid-range markets are saturated. Buildable, but not likely saleable. > Top end market is pretty tight. R&D budget for that level of gear is > probably more than the video card project. Semi-pro is more doable. > > Best bet is an aggressive design to sell on performance and features. Most > advanced features can be implemented in software, so the hardware should be > fairly straight-forward, but it still needs good throughput. > > Target market > Semi-pro audio (high end of target) > High end gamers (mid range of target) > Home theater (low end of target) > Hobbyist > -Hobbyist add-ons could greatly increase saleability to other markets > US$300? price range for baseline system - this needs to be priced out > 19" rackmount boxes may cost more. Mainly due to the sheer volume of good > stuff that can be packed into them. see below. > > > Features > 192kHz @ 24bit inputs and outputs (48 bit fixed point internal) > on board resampling/mixing > sample rate > bit depth > # channels > channel swap > on board realtime compression/decompression/transcoding > all analog I/O is in (shielded) breakout boxes > more than one kind of box supported (including custom boxes) > more than one box at a time supported > breakout boxes may be up to 100m from host system > MIDI > 5.1 optical > ADAT > sound samples/effects may be preloaded to card and played/mixed on demand > full 3D audio processing > custom codecs and effects generators may be loaded on demand > on board speech synthesis - just another codec :) > on board speech recognition - same :) > IR remote control? > watchdog timer? > > > Several people have voiced desire for 192kHz capability and have indicated > media at this quality is available from some sources. > > Native sample capabilities > 192kHz at 24 bit max - more than this would be overkill, and would hurt > other capabilities without benefit > 96kHz, 48kHz, 44100Hz, 22050Hz, 11025Hz for good measure > -there is no point resampling to a higher rate unless you are going to mix > with a higher rate source. digital resampling does not increase sound quality. > -resampling from 44100 (CD audio) and lower to 48k or higher creates > artifacts (not an even multiple) > -more processing power/bandwidth is available for effects/additional > channels at lower sample speeds. halving the sample rate doubles the > processing power available per sample. > 48 bit fixed point internal DSP for best accuracy > all samples converted to 48 bit fixed point for internal processing > -there should be no data loss from this conversion > -if the hardware is efficient: > -there should be negligible performance penalty for conversion > -there should be no performance penalty for using the higher bit depth > -simplified design if all DSP functions and codecs use the same format > -downsampling from 48 to 24 bit for output is trivial if implemented in > hardware > > > World clock > world master capable > may also use external world clock > -card can repeat clock to host system and breakout boxes > if no dedicated world clock wiring is desired or possible, soft world clock > may be implemented > -ie card and each peripheral generate their own clock and a periodic sync > signal is provided over data channel. see below. > -unit may not be able to run at full speed due to timing constraints/clock > skew in this case. not acceptable for live work, but OK for lower markets. > > > Virtual back plane for maximum flexibility (any input may be mapped to any > output with any filtering/effects) > external effects box can therefore be patched in at any location, if desired > volume controls are 10-12 bit analog inputs > sample at 20Hz? > volume control sampling does not need to be synchronized to any world clock > mutes are 1 bit input arrays. same sampling as above. > > > I/O > card is purely digital > all analog and most digital I/O is in breakout boxes. see below. > > Analog > inputs and outputs are discrete from each other (no dual I/O jacks to toast > a mic with) > powered outputs are discrete from line outputs > 1/8", 1/4", RCA, balanced XLR as appropriate > inputs > digitally controlled analog gain or preamp for each channel > analog prefilters to reduce digital aliasing > digital post filter? (cropping excess digital bits is trivial) > outputs > digitally controlled output gain or postamp > 5th or 7th order Bessel filters standard > > Digital > optical S/PDIF in and out (5.1 audio) > ADAT (lightpipe) in and out (8 channel, optical) > does anybody have specs on this? > how hard is it to get interface hardware? > cost? > licencing? (this is an open design, so this could be an issue) > MIDI > CD digital audio in/out (2 channel, 16 bit, 44100, twisted pair) > this would be on-card, if provided > could be used to link to other cards > > > Breakout Boxes > more than one type of box should be supportable > > 5 1/4" internal/external box? > cheapest to build > shielded for internal mounting > line in/line out/mic/headphone/IR/MIDI > 5.1 line out? > volume control input > may only need 100baseT if bandwidth isn't a problem > > 9" (approx) external box > home theater/gamer > 5.1 analog and optical in/out > 5.1 analog speaker out (power amp) > (5.1 analogs can be configured as 3 stereo pairs, or 6 mono) > IR/MIDI/mic/headphone > software controlled AM/FM radio tuner? > LCD display? > digital spectrum analyzer display? > > 19" rack mount (someone with experience could probably give better layout) > > I/O patch board > 60-80 ports > 1/4", balanced XLR (with switchable phantom power), headphone > 1-2 volume controls per column > ADAT in/out > MIDI > world clock in/out > 1000baseT > > Control box > 8-16 ports > 1/4", XLR (with switchable phantom power), headphone > ADAT in/out > MIDI > world clock in/out > 32 volume control sliders with mutes (2 banks of 16) > 4 master volume sliders with mutes (same as above, just labelled > differently?) > knob switches? (to select option or backplane presets, etc) > 2 16 pos switches could be encoded in a byte or 4 4 pos switches, etc > digital spectrum analyzer display? (also a programmable output) > -this would suggest an equalizer somewhere would be in order too :) > peak/RMS volume readouts? (which they are is a setting) > 1000baseT > > more than one box at a time should be supported > master can command boxes to forward streams to each other directly? > multi master? > ie more than one card connected to a group of breakout boxes and each other > more complex design > allows cards to talk to each other directly or share I/O resources > 1000baseT connection > NOT TCP/IP or IPv6 - should NOT be WAN routable > don't need the extra overhead > somebody is going to want to use the same switch their internet connection > goes through.... > all analog audio channels are 24 bit > volume control channels are 10-12 bit > mute controls are bit arrays > requires in-box microcontroller > as much work as possible should be done in hardware > minimal processing requirements due to simple protocol > ECC encode/decode/fixup is a large part of workload > no DSP capability, other than perhaps hardware filters > any digital filtering should be done by Master unit > simple remote commands > box detection broadcast (true PnP) > per channel input signal forwarding (either to output on same box, output > on other box, or to Master) > world clock mode selection > set gain controls > box identification > manufacturer > model > serial number(optional) > I/O count/descriptions > read current settings > main load is data stream > latch and marshal input signals for transmit (controlled by world clock) > unmarshal packets to output signal latches > 2 stage latch stepped by world clock > lesser load is volume/mute update stream. same profile, just lower bandwidth > > > I/O bandwidth > 192kHz at 24bit is 576000 B/s > 48kHz at 24bit is 144000 B/s > > max channels for 24 bit audio > 192kHz 48kHz > 10baseT 1 6 > 100baseT 17 69 > Firewire 69 277 (400MHz) > 1000baseT 173 694 > > 100MHz could barely handle 17 channels @ 192kHz > if you add ECC (usually a good idea) it would be even less > Firewire can handle up to 69 channels (less for ECC), but protocols/drivers > are a mess > -how much does firewire hardware cost compared to 1000baseT? how to get? > -Firewire2 at 800MHz might be a possibility, but again, cost/availability? > > > Master Unit > 1/2 height 1/2 length card > PCI or PCIe form factor > PCIe > should be main focus > offers higher bandwidth/lower latency than PCI > common on newer machines > by the time this gets to market, this will be the dominant standard > x1 should be fast enough > PCI > provided for legacy support > large current install base > limited lifetime > 1000baseT external connector > 100 or 1000baseT internal connector (depending on cost and whether the 5 > 1/4" box needs 1000baseT) > world clock in/out (to connect to another card in the same computer) > ADAT I/O? > 5.1 optical out? > RAM > 32-64 MB (128?) > DDR > dual channel? > CPU > 200MHz minimum > can we do 300MHz, or even 400? > overclockable with active cooling? > 3rd party fan/water cooling mounts > dual core? > RISC like instruction set > 48 bit fixed point DSP instructions or DSP farm > 8-32 bit integer math (48 bit integer math?) > bitwise functions > should be efficient for compression/decompression using various codecs > 32 bit address path so memory is upgradeable just by modifying the PCB > I/O controls/registers should be separate bus, so memory map is linear > minimal onboard boot loader, if required. all software is loaded from host > system > separate data and instruction L1 caches > MMU so codecs run in own memory, don't direct have access to hardware > necessary for buggy or untrusted codecs > DMA to access host computer memory > accelerated task switching > multiple register files? > OS > embedded Linux to start with (at least until design is proofed) > a true RTOS would be preferable > multi-tasking > SMP capable if CPU is dual core > zero copy IO for performance > will take a while to write :P > maybe hack Linux? that is what it is for, after all > on board watchdog timer? > good if she locks up > can be used as host computer watchdog timer as well > hardware random # generator? > can be used for white noise production > > > 3 profiles of signal handling > Live > this is usually going from an analog input to an analog output > highest priority in processing > minimal buffering to reduce delay > needs to be < 20ms, even if signal is passed through card more than once > eg input -> card -> external effects box -> card -> output) > this puts the highest load on the card > critical for audiophiles > may be important for gamers and hobbyists > minimal importance for home theater > Real-time > this could be recording or playback > precise timing is only necessary at source or output, respectively > double buffering to improve efficiency is an asset > even 500ms delay playing an MP3 doesn't matter. prebuffering several > seconds wouldn't hurt anything either. > video sync isn't affected if the timing signal back to the computer is > generated AFTER the decompression codec output buffer > double (or more) buffering during recording is critical to prevent data > loss, especially if the audio is being compressed in real time > Transcode > lowest priority - this could be done entirely using time left over from the > other operations > buffering to improve efficiency is an must > delay, clock skew, etc don't matter > could be used with non-audio data with appropriate codecs (SETI at HOME, > anyone?) > > > If I have missed or messed up anything, that is just me being me. Please > feel free to correct/mock/browbeat as appropriate. :) > > _______________________________________________ > Join Excite! - http://www.excite.com > The most personalized portal on the Web! > > >
