[alsa-devel] alsa-lib rate plugins - float samples - patches
pavel.hofman at ivitera.com
Fri Jul 1 11:50:17 CEST 2011
Dne 1.7.2011 11:35, Takashi Iwai napsal(a):
> At Fri, 01 Jul 2011 11:27:03 +0200,
>> Hi Takashi, thanks a lot for your reply. Would moving the new method to
>> the end of snd_pcm_rate_ops struct suffice?
> This is needed together with the API version bump.
> Increase SND_PCM_RATE_PLUGIN_VERSION, change rate_open_func() to call
> all older versions, and don't use the new methods for older versions.
OK, I will fight it :)
>> Or do I have to create a new
>> API number with corresponding checks? I am afraid the latter is the case :)
>>> - From the performance POV, we may need to have the built-in
>>> float conversion in rate plugin indeed. Anyway, if rate plugin
>>> supports float, it should add FLOAT as the supported format.
>>> This needs changes in the parameter setup in rate plugin.
>>> Then it should accept the float format as is without conversions.
>> If I understand correctly, the rate plugin accepts only linear formats
>> now. What was the original reason to exclude float?
> Because the existing rate-converter are only for linear formats :)
OK, I will try to provide automatic conversion to/from floats in the
rate converters in alsa-plugin git for the new API version to include
>> The "convert" API
>> method is generic enough, perhaps I should add float support to all the
>> rate converters using the API "convert" method. Again there is the
>> question of new API version - the new one would offer convert_float and
>> allow float samples in the generic convert method.
>> The specific convert_s16/float methods in pcm_rate.c can be modified to
>> accept float too.
> I don't mind how it'll be implemented as long as the backward
> compatibility is kept somehow.
Backward compatibility - I assume you mean any combination of alsa-lib
and alsa-plugins :) OK, I will try.
> HAVE_SOFT_FLOAT is a bit confusing name. It means actually NO_FLOAT,
> or better to say, NO_FLOAT_CALCULATION. Thus ifndef is correct
OK, how about if I rename the constant accordingly?
>> Well, the libsamplerate is using float internally, I am afraid the
>> float-less case would require disabling this rate converter alltogether.
> Currently yes, but who knows in future? The library internal can
OK. I will make patches for alsa-lib first and then we will see.
More information about the Alsa-devel