tir, 09.03.2004 kl. 15.26 skrev Paul Davis: > >And by that time, games will be even more demanding than before, and > >still want to use those cycles for itself rather than software sound > >processing, so just sitting idle waiting for the ultimate > >infinite-megahertz cpu, that can do everything in no time, gains nobody > >anything... at least our business won't. > > but don't you also want to be able to sell as many copies as possible > to as many satisfied customers as possible?
I suppose that's basically the idea. Customers want full support for their hardware. Which includes HW mixing. > if so, you have to pay > attention to whatever standards can be found for the domain at > hand. in this case, the AC97 codec spec (and its recent successor > whose name i forget) is about the most relevant thing i can think > of. AFAIK, AC97 etc. say nothing about the kinds of gain control and > mix routing that exist for multiple PCM streams. Yeah, we could consider AC97 to be a lowest common denominator. (That's not to say it is, since very old sound cards won't be compliant.) > ergo, there is no > standard way to do this that will work across a significant fraction > of the installed and/or potential user base. Are you mocking ALSA's plugin interface, too? Is there no "standard way" to play 22.050kHz streams using e.g. plughw? Or is plughw a design mistake? It can't be extended to use the route/volume plugin to adjust the volume of the stream in a "standard way", I suppose? > so, either ALSA can come up with such a thing, which might be > interesting but the manpower available to work on it is very limited, > or parties that have a vested interest in it can use an existing API > (SDL springs to mind, though i've never looked at it) or develop a new > one that provides a standard mechanism for doing wat you want. That's always going to be the case. It's Using Open Source In Business 101. > i mean, even at the most basic level, the audio interface that is > built into my laptop motherboard (some intel nonsense) cannot do any > sample rate other than 48kHz! this is a high end laptop (HP Pavilion > zd7000, 3GHz processor, 1440x900 display, etc) ... think of the cycles > that will be spent *resampling* your audio independently of the mixing > step. Independently? No, our software mixing code resamples, adjusts volume, and mixes the stream into the buffer in one step. That's one reason we've decided not to use ALSA's plugin system, as they do it in several steps (you'd have to run it through the rate plugin, the route/volume plugin, and finally the dmix plugin). For best performance, we resample on our own when the sound chip is locked to 48kHz (if we didn't, we might end up letting each sound go through *two* resampling steps - one from the sound effect's sample rate to the mixer stream's sample rate, and another from the mixer stream's rate to the sound card's physical rate if they don't match, therefore it's better to simply make the mixer stream's rate match the sound card's, so that each sound effect is resampled once and only once). > this type of BS seems to be growing more and more common. Perhaps they're thinking like you seem to, that the rise of CPU power will make hardware features obsolete. "Hardware has limitations, software don't." Same thing with winmodems. Why then do companies like Creative churn out sound cards with ever more powerful hardware features, if you're saying nobody should ever write code to take advantage of those hardware features? Since we're ranting anyway: It's a similar situation with 3D graphics hardware, where the 3D cards get ever more powerful, even though the CPU power is going up. And yet the OpenGL folks (at least those working on DRI) say "it's not important for the app to know whether something is done in hardware or not", which I have yet to make sense of given the trend. It's obvious that the greatest in-game 3D on the planet could not be done in smooth realtime on just a CPU without a GPU (particularly when the CPU is also supposed to control enemy AI, make 3D environmental effects on a 48kHz single-stream AC97 chip, communicate with other players via a winmodem, and so on), so why shouldn't there be a feature to tell that certain advanced 3D effects *could* be offloaded to hardware without getting more CPU load? > if i > was in your position (specifically, if i have to assume that my user > base spent a (comparatively) lot of money on a graphics card, maybe > even paid for a 5.1 speaker setup, but are still using the > factory-provided audio interface, i would assume the absolute worst > capabilities for that interface that i could: single sample rate, > single PCM stream, no mixer. Assumptions are seldom worth much. We're not going to assume anything here. If the card has sufficient hardware features, we wish to use them for what they're worth, since that's what they're there for. If it doesn't have them, then we obviously fall back to the old software mixing code that's been in our codebase forever. Is a customer who says "I spent $500 on this new great sound card, but the sound is just as lousy as before" a happy one? I think not. > and btw, i wasn't suggesting that you just "sit there waiting". my > point was that the time you might spend working on this could be spent > working on something else, and by the time you're done, CPU speed > increases will have done this particular task for you. If ALSA provides the interface, it's just a matter of using it instead of software mixing. There's no magic involved that's going to take man-years to accomplish. ------------------------------------------------------- This SF.Net email is sponsored by: IBM Linux Tutorials Free Linux tutorial presented by Daniel Robbins, President and CEO of GenToo technologies. Learn everything from fundamentals to system administration.http://ads.osdn.com/?ad_id=1470&alloc_id=3638&op=click _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
