Author Archives: Pavel Hofman

Download your current kernel headers: sudo aptitude install linux-headers-$(uname -r) If the command fails with “not found” error, install headers package appropriate for your running kernel. Or install whole kernel source by sudo apt-get source linux-image-$(uname -r) Download development software stack: sudo aptitude install kernel-package Clone git sound tree: git clone https://kernel.googlesource.com/pub/scm/linux/kernel/git/tiwai/sound.git If needed, switch to another branch: cd sound git checkout -b ak411x-fix remotes/origin/topic/ak411x-fix cd .. Clone git alsa-driver-build tree: git clone https://kernel.googlesource.com/pub/scm/linux/kernel/git/tiwai/alsa-driver-build.git Setup alsa kernel, configure, compile: cd alsa-driver-build.git/alsa utils/setup-alsa-kernel ../../sound ./gitcompile If your kernel headers are located in a different directory than /usr/src/linux-headers-$(uname -r), specify the path … Continue reading →

Pulseaudio with default-sample-rate=192000 and resample-method=src-sinc-best-quality takes about 90% CPU on my i5, aplay via default (pulse plugin) complains about xruns, pulseaudio gets killed eventually (I do not know what kills it, CPU ulimit is unlimited, probably some laptop service watching CPU hogs). Simply starting pulseaudio with LD_PRELOAD LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libsoxr-lsr.so.0 pulseaudio drops pulseaudio CPU load down to 6-9% while resampling running (checked in the card’s hw_params). That was simple 🙂 Integrating with client-spawn pulseaudio Tested on Mint15: 1. Create executable script /usr/local/bin/pulseaudio.sh. Make sure to use correct path to your libsoxr-lsr library: #! /bin/bash export LD_PRELOAD=/usr/lib/x86_64-linux-gnu/libsoxr-lsr.so.0 exec /usr/bin/pulseaudio $@ Do not forget … Continue reading →

Since my previous post the great libsoxr library incl. the libsoxr-lsr variant has become part of debian testing/ubuntu repositories. It means we can easily use it instead of libsamplerate now. Just install the package: pavel@samsung ~ $ aptitude search libsoxr p libsoxr-dev – High quality 1D sample-rate conversion lib p libsoxr-dev:i386 – High quality 1D sample-rate conversion lib p libsoxr-lsr0 – High quality 1D sample-rate conversion lib p libsoxr-lsr0:i386 – High quality 1D sample-rate conversion lib p libsoxr0 – High quality 1D sample-rate conversion lib p libsoxr0:i386 – High quality 1D sample-rate conversion lib sudo aptitude install libsoxr-lsr0 Check contents … Continue reading →

Preliminary results of libsoxr integration Plugin rate API modified to allow float. This avoids the information loss of int24->int16 conversion currently occuring in alsa-lib (int24->float32 is bit perfect). Libsamplerate (and libsoxr) use float internally. The sweep file generated by: sox -V -r 44100 -c 2 -s -b 24 -n sweep.wav synth 10 sine 1:22000 vol -6dB Spectrum of the sweep sox sweep.wav -n spectrogram -w Kaiser -z 180 -o spectrum-sweep.png Devices defined in .asoundrc: pcm.raw { type hw card 0 device 0 format S32_LE } pcm.flexibleraw { type plug slave.pcm raw } pcm.dumpratefile { type file #slave.pcm flexibleraw slave.pcm null … Continue reading →

Here is a simple script for A/B testing. Just modify the CONFIG section to your needs, or feel free to rewrite completely 🙂 Continue reading →