ons, 10.03.2004 kl. 10.46 skrev Giuliano Pochini: > On 09-Mar-2004 Ove Kaaven wrote: > > 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. [...] > > No need to enter the philosophycal battlefield.
Oh, I wasn't planning on it. I didn't say that to make an argument or anything, just because "we're ranting anyway". Consider it venting, or whatever, I'm not trying to persuade you, just make it clear that I have an opinion which it's not worth Paul Davis's time to try to change. I'm not trying to push that opinion on him or anyone else, just make it clear that they shouldn't try to push theirs on me either, and then we can get along together, agreeing that we disagree. > The fact it there is > no ALSA support for this yet. Thus, you can just await for it, or use > another mixer library, or help ALSA developers to write it. That point has already been made, and agreed upon. And not really what we were debating, either. > Please start writing what the API should provide. Well, the requirements that raised this thread should be fairly clear. For example, ALTERNATIVE 1 snd_pcm_set_volume(snd_pcm_t* pcm, int volume) and snd_pcm_set_pan(snd_pcm_t* pcm, int pan) using whatever value range makes the most sense, and perhaps some query on whether these controls are available from the pcm info. It's acceptable to have to explicitly ask for these controls using hw_params. The plug plugin could insert the route/volume plugin if these controls are asked for. ALTERNATIVE 2 snd_pcm_set_volume(snd_pcm_t* pcm, int vol_left, int vol_right) but I don't expect this to be useful, since there are probably some oddball devices out there that aren't able to control left and right volume independently like this. ALTERNATIVE 3 Let each PCM channel have its own mixer control, like the EMU10K1 currently do. That is, use snd_pcm_info_get_subdevice() to get the index, then look up a volume control with a well-known name and the given index using the snd_ctl API to control the volume of that PCM stream. The name and semantics of that mixer control would have to be standardized and be the same on all devices that are capable of this feature. Whatever way is chosen, it's simple enough to work with. But if we get into the realm of spatial sound, it can get trickier, of course. I might suggest to create a new snd_pcm_fx_params_t or something, which can be loaded into a PCM stream to change the volume, pan, or other effect. The available effects should depend on which was requested in hw_params. Specifically, the following effects would be desirable: * Volume * Pan (not available if 3D sound is requested) * Frequency (can be used for software-calculated doppler shift, or for "wavetable synthesis"-like purposes) * 3D position (relative to listener) * Velocity (for hardware-calculated doppler shift) * Cone inside/outside angles, direction, outside volume * Min/max distance (wherever the sound is heard) There are also settings that can be considered "global" for all sounds in the game, but I'm not sure how they could really be considered such using the PCM API, so it's acceptable to have to go through every PCM stream and update the parameters of each one, if that's easier to implement. If not, there must be a way to attach each 3D-aware PCM stream to some kind of master structure which can hold these parameters. This master can be a designated PCM stream with special hw_params. Global settings include: * 3D position, orientation (forward and upward directions), and velocity of listener, to allow streams to use absolute, not relative, coordinates, if they want to * Distance, rolloff, and doppler factors (I don't remember the exact semantics of these, but can look it up) These will be required anyway for full HW-accelerated OpenAL support, of course. The API should also be designed to allow for further parametrized effects to be applied to a particular stream, for example reverb effects. For what it's worth, DirectSound has currently defined Gargle, Chorus, Flanger, Echo, Distortion, Compressor, and a couple of Reverb types... ------------------------------------------------------- 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
