From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stas Sergeev Subject: Re: sound support Date: Wed, 09 Mar 2005 22:31:17 +0300 Message-ID: <422F4F05.2080705@aknet.ru> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-msdos-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: linux-msdos@vger.kernel.org Hello. Ryan Underwood wrote: > Yeah, that is a big problem because > everyone is using a callback model > these days I am not sure we can't try to use the callback model, it may just be inefficient. That also depends on how's the server reacts on the partially satisfied request (i.e. it asked for XXX bytes, but we only give it a half of the size or so). If the server have no problem with that, we might still be able to calculate how we have to speed the DMA up or down. >> It just sums the values of the streams. >> I don't know how good it mixes more than >> 2 streams. > I know this is false because I have played What exactly of the above, on your opinion, is false, btw? The "it just sums the values...", or the "I don't know how..." statement? Or do you think just summing the values will produce the good results for many streams? Here's the quote: --- The resolution for 32-bit mixing is only 24-bit. The low significant byte is filled with zeros. The extra 8 bits are used for the saturation. --- For the 16bit streams there might be all the 16bits for saturation, but with more than 2 streams the losses are unavoidable, and consider that the physical output is usually only 16bit, not 32. >> way dmix is implemented, its use is very >> limited. Well, not our problems at all. > It might be a good question for the ALSA list. It is not a question, this all is even documented. >> Isn't it what's the O_NONBLOCK for? > Here is Takashis' reply to a Linus rant: Wow, amazing! O_NONBLOCK is not for that, now I see. I wasn't aware such a seemingly obvious things of the standard can sound so different when Linus explains it:) > There is disagreement, but most kernel developers who responded thought > that O_NONBLOCK to avoid hanging the app was silly. If the app wanted > to wait for the sound device to become available, it makes more sense > to loop until not errno==EBUSY. I don't think they (Linus mainly) offer such a silly thing. His point it that the synchronization on the sound device is silly and must not be done (no sane program should lock up and wait for the device to free, as this may take from seconds to years). And --- If you actually think this is a useful feature, I would suggest trying to key it off O_EXCL or a new flag. --- Actually reading that discussion was both informative and fun. Yes, I find it funny to see how easily Linus beats his opponents even on the things that initially look obviously not on his side, and how easily he proves what initially looks obviously wrong. That's something;) > Ok, so what you mean is that we must > have precise, low latency control > over what is written to the buffer. No, what I mean is that we have to try to advance the emulated DMA with the constant speed. That means we shouldn't do the callbacks to it and request the data from it to fill the buffer. Instead we'll have to do the buffering on an SB side (SB have the FIFO actually), and SB needs to have the information to be able to adjust the speed of the emulated DMA to match the speed of the real output. It is probably more difficult to implement with callbacks, but it may be possible. The DOS program must see the DMA to advance smoothly, but we can still do some buffering on an SB side. The good thing is that the current DMA implementation will work, it is only the SB layer that will require some work. Of course the most frightening part is to put the stuff into a separate thread. > Isn't it possible for a BSD port too? It might be (it was done in the past), but it may be feature-less and difficult to maintain. Linux kernel have a lot of dosemu-related patches in it, dated from the beginning of the project to nowadays. And I personally (which may be totally wrong) don't see a lot of demand for that. Linux is always the primary "market", but perhaps the windows port will have some market too. Not sure, but it worth to try imo. > dosbox and qemu and > complaining about the speed Is qemu still slow, even with its new proprietary virtualization technology (or whatever that kqemu is)? From what I've heard (not too much), it may be faster than dosemu. >> are is much appreciated. x86_64 port is >> probably more difficult, but can and must >> be done. > By this you mean using a CPU emulator For realmode only. Not a big deal. We could even use simx86, but unfortunately it broke. > In this case we are losing the > speed of native CPU, native IO, VESA > console (vs vgaemu). I'm not sure > how it would turn out. On 64bit machines? It might be very fast. Emulating realmode code is not a big deal *at all*. And even the protected mode user-space code is not much of a slowdown when translation is used, I beleive. The real problem is with the ring0/system code, which we always can avoid to execute. >> qemu-user development, and qemu-user no >> longer runs dosemu (while it used to do > Have you mailed him with that problem? Yes, long ago. He said he isn't going to invest any more time in the qemu-user development. > Well, we are running protected mode OS too, > as long as there is a DPMI > interface and we can find it. :))) Guess where's the DPMI come from? It was developed by MS as a quick hack to be able to run the windows kernel in protected mode without too much of a redesign. Then there was a DPMI committee, but I don't think any other OS have ever used that API. > The LDT emulation was the only other > problem, wasn't it? For Win31? Sure. (plus tons of the DPMI and extender improvements) > Do you have information on this? I didn't > know there was any special > virtualization capability of x86-64. Nothing except for the some announcements: http://www.extremetech.com/article2/0,1558,1644513,00.asp And for Intel: http://www.intel.com/technology/computing/vptech/