[alsa-devel] alsa-lib rate plugins - float samples - patches

[Pavel Hofman]

Dne 20.6.2011 09:35, Pavel Hofman napsal(a):
> Hi,
> 
> This is probably a question for Jaroslav Kysela. The better-quality rate
> plugins offer float resolution, but currently we are deliberately
> loosing information by down-converting to s16 in plugin_rate API
> (convert_s16). In rate_samplerate.c, the samples are up-converted to
> float before calling the libsamplerate API. Speex offers float API too,
> while we are using the int16 one.
> 
> There are two ways to handle this:
> 
> A. Implementing the generic "convert" API function for these plugins,
> handling the sample - float conversion in each plugin individually.
> 
> B. Extending the pcm_rate API (pcm_rate.h) with a new optional function
> convert_float.
> 
> Since the conversion from general sample format to float is not trivial
> (using the plugin_ops.h operations), I would be inclined to suggest the
> extension (well I have it hacked already :-) ). On the other hand, the
> conversion routine can be located in some common code shared by all the
> plugins involved and we could keep the existing API, using the generic
> convert function.

I am attaching preliminary patches. May I ask for help with adding a new
API version number if you find it necessary? I am afraid this is beyond
my skills.

The patches are not checkpatched yet.

After these patches are finished, I would like to work on implementing
the SoX resampler algorithm which features excellent CPU
consumption/resampling quality ratio.

Thanks a lot.

Pavel.
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