On Sun, 21 Dec 2003, Manuel Jander wrote:
> Hi,
>
> I updated my ALSA- OpenAL interface proposal, taking into account some
> suggestions i have received, and some further investigations, specially
> on the side of OpenAL.
>
> Take a look at:
> http://galadriel.mat.utfsm.cl/~mjander/aureal/alsa/OpenAL-ALSA.txt
>
> AFAIK, the linux OpenAL port was not designed taken any hardware support
> into account.
>
> Things that go against my goals are:
>
> - OpenAL only uses one single ALSA substream. There is no substream
> management (must be added).
> - OpenAL is not hardware mixing aware.
> - OpenAL ALSA structs must be changed to integrate hardware context
> data.
>
> Things that are favorable:
>
> - As far as i dug into OpenAL, it seems that all source buffer
> processing is done in one single place (_alMixSources). Replacing this
> call for hardware assisted sources seems feasible.
>
>
> The same as for the first iteration of this proposal, please take some
> minutes and give some comments/suggestions back. I need feedback.
Ok, regarding the last feedback:
1) try to make all controls non OpenAL specific
- naming should be generic something like - "Ext3D ..."
- the ranges and usage might be different per hardware
2) alsa-lib should provide a common entry point for all 3D APIs
- I propose to have a special name for stream like "surround3d";
note that stream in my eyes is one "voice"; we can use hw mixing
or dmix in case when hw mixing is not available for final output
- we need to add runtime controls for PCM streams to alsa-lib (see bottom),
these controls will eventually map to hw controls or they won't be
present in case when hardware acceleration does not exist
Proposal for runtime PCM controls:
==================================
int snd_pcm_control_list(snd_pcm_t * handle, snd_config_t ** list);
int snd_pcm_control_set(snd_pcm_t * handle, snd_config_t * value);
int snd_pcm_control_get(snd_pcm_t * handle, snd_config_t * value);
A short description: snd_pcm_control_list() returns a compound with list
of all keys (names of variables - controls - assigned to a PCM stream) and
other useful information (ranges, types, user representation etc.).
snd_pcm_control_set() and snd_pcm_control_set() functions will set and get
the contents of value identified by given key.
Note that value might be also a compound so very complex data structures
might be passed through.
Jaroslav
-----
Jaroslav Kysela <[EMAIL PROTECTED]>
Linux Kernel Sound Maintainer
ALSA Project, SuSE Labs
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