[pulseaudio-discuss] Palm's PA patch

[pl bossart]

The resampling part makes complete sense. Palm are using a polyphase
fixed-ratio filter; this will be more optimized than the variable-rate
interpolation provided by libspeexdsp (no need to be variable-rate for
file playback, only needed when devices are not clocked off of the
same reference). The footprint of additional tables is negligible in
light of the MIPS savings.
Looks like there's a 4-band EQ implemented with biquads applied just
before writing the data to ALSA buffers. Not sure if this is the right
thing to do if PA rewinds and remixes, they would need to keep the
filter state. Not sure either why they released the filter
coefficients and algorithm, usually this is the secret sauce you never
provide to anyone.
The bad thing is that we now have at least four independent audio
policy modules in various PulseAudio implementations, each requiring
apps to use a specific interface. Sockets, DBUS, callbacks, you name
it, life just became more difficult for application development.
Cheers
Pierre

On Fri, Jun 19, 2009 at 7:43 AM, Lennart
Poettering<lennart at poettering.net> wrote:
> On Fri, 19.06.09 09:31, Colin Guthrie (gmane at colin.guthr.ie) wrote:
>
>> Joking aside, it's good to see this patch. Am I right in saying that
>> they didn't actually need to share it due to the LGPL side of things? If
>> so good on them for releasing it all the same :)
>
> LGPL is not BSD. Of course they had to release their patches. What
> they didn't have to release is stuff they dynamically link into
> PA. But all changes on PA's sources themselves they had to release.
>
> Lennart
>
> --
> Lennart Poettering                        Red Hat, Inc.
> lennart [at] poettering [dot] net
> http://0pointer.net/lennart/           GnuPG 0x1A015CC4
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