First, update to latest kernel and firmware. This brings minor usb optimizations, unfortunately the bugs affecting over 44,1 khrz playback are still present. The foundation reported to be working hard on the matter (they hired a specialist to solve the issue, at least that’s what i got…)

sudo apt-get install git-core
sudo wget http://goo.gl/1BOfJ -O /usr/bin/rpi-update && sudo chmod +x /usr/bin/rpi-update
sudo rpi-update

Then, we’ll strip down the distro. This aims basically to use less disk space, but less processes active (especially X graphic user interface) leave the pi arm cpu quieter. Some folks believe that less processes running= better sound. I am not one of those. I indeed can say that less cpu used= less power drain and more responsive system. This can indirectly improve playback quality, also for electrical inducion reasons. But my physics knowledge is not enough to explain clearly the reason why.

Sudo apt-get update

Getting a list of all packages installed give us an idea of what we can remove.

dpkg --get-selections

Let’s remove what we don’t mind to use

sudo apt-get remove aspell desktop-base desktop-file-utils dictionaries-common dillo fonts-droid fonts-freefont-ttf fontconfig fontconfig-config galculator gnome-icon-theme gnome-themes-standard gpicview gsettings-desktop-schemas gsfonts gsfonts-x11 hicolor-icon-theme leafpad lightdm lightdm-gtk-greeter lxappearance lxde lxde-common lxde-core lxde-icon-theme lxmenu-data midori mime-support openbox omxplayer penguinspuzzle x11-common wpagui python3 python3-minimal python-pygame x11-common

Python games? Glad to ask, but no.

sudo rm -rf python_games

Opt contains lot of heavy stuff, such like a damn 1080i video.

sudo rm -rf /opt/vc/src/hello_pi/hello_video/

Python, go away!

sudo apt-get remove `sudo dpkg --get-selections | grep -v "deinstall" | grep python | sed s/install//`

Removing gcc, we’ll install latest version later

sudo apt-get remove gcc-4.4-base:armhf gcc-4.5-base:armhf gcc-4.6-base:armhf

Clean unnecessary packages

sudo apt-get autoremove
sudo apt-get clean

Ok, now let’s update the software environment

sudo apt-get update
sudo apt-get upgrade

sudo apt-get clean

let’s check how much space did we free up:

df -h

Filesystem Size Used Avail Use% Mounted on
rootfs 1.8G 870M 804M 52% /
/dev/root 1.8G 870M 804M 52% /
devtmpfs 235M 0 235M 0% /dev
tmpfs 49M 252K 49M 1% /run
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 98M 0 98M 0% /run/shm
/dev/mmcblk0p1 56M 21M 36M 37% /boot
tmpfs 98M 0 98M 0% /tmp

870, could be worse

We don’t need swap. Do we?

sudo swapoff -a
cd /var
sudo dd if=/dev/zero of=swap bs=1M count=100

Now, we’ll install Mpd. We will now get and install the vanilla package, the one provided with debian. We will use this to get it’s infrastructure, and then we’ll install latest version from source.

sudo apt-get install mpd mpc

Now we install both prerequisites to compile mpd and mpd’s dependencies

sudo apt-get install aptitude wget binutils gcc make subversion autoconf automake autotools-dev libtool pkg-config build-essential libncurses5-dev libncursesw5-dev gcc libglib2.0-dev

sudo apt-get install libfaad2 libfaad-dev libflac8 libflac-dev libogg0 libogg-dev libvorbis0a libvorbis-dev libid3tag0 libid3tag0-dev libmad0 libmad0-dev libcue-dev libcue1 libasound2 libasound-dev libasound2-dev libao-dev libwavpack-dev libwavpack1 libsamplerate0 libsamplerate-dev libmikmod2-dev libmikmod2 libmikmod-dev libshout-dev libavformat-dev libavcodec-dev libavutil-dev libaudiofile-dev libcurl4-openssl-dev libmms-dev libmms0 libtwolame-dev libtwolame0 libmp3lame-dev git-core

Now, we clone the official mpd repo, in order to obtain and compile latest mpd version. As root:

sudo su
cd /home/pi
git clone git://git.musicpd.org/master/mpd.git

cd ./mpd

./autogen.sh

We then configure it to use few options, making mpd more lightweight.

./configure --disable-bzip2 --disable-iso9660 --disable-zzip --enable-id3 --disable-sqlite --enable-ffmpeg --enable-alsa --disable-wave-encoder --enable-pipe-output --enable-httpd-output --disable-recorder-output --disable-sndfile --enable-oss --enable-shout --disable-pulse --disable-ao --disable-mad --disable-inotify --disable-ipv6 --enable-curl --disable-mms --disable-wavpack --disable-lame-encoder --disable-twolame-encoder --enable-vorbis --enable-lsr --with-zeroconf=auto

make
make install
sudo su
/etc/init.d/mpd stop
echo DAEMON=/usr/local/bin/mpd >>/etc/default/mpd
/etc/init.d/mpd start
mkdir -p ~/.mpd/playlists

Now, we’ll start configuring mpd, editing the mpd.conf file

sudo nano /etc/mpd.conf

What interest us is:

#group "nogroup"

Becomes

group "audio"

Mpd will belong to “audio” group, which will be useful for setting mpd’s priorities.

Then

bind_to_address "localhost"

that will become

bind_to_address "any"

Activating auto-update by uncommenting following line, this will enable mpd to automatically update its music database when something new is added or removed.

#auto_update "yes"

Then

audio_output {
type "alsa"
name "My ALSA Device"
device "hw:0,0" # optional
format "44100:16:2" # optional
mixer_device "default" # optional
mixer_control "PCM" # optional
mixer_index "0" # optional

that will become

audio_output {
type "alsa"
name "USB Dac"
device "hw:0,0" # optional
format "44100:16:2" # optional
# mixer_device "default" # optional
# mixer_control "PCM" # optional
# mixer_index "0" # optional

Then we’ll uncomment the lines regarding the buffer

audio_buffer_size "2048"
buffer_before_play "10%"

Ctrl+ x to save, then y to confirm.

Now we assign to our usb dac the device number 0, which is the default for mpd and the mixer. We can do so by commenting out the line

options snd-usb-audio index=-2

in

sudo nano /etc/modprobe.d/alsa-base.conf

By doing so, RaspyFi will use as default the USB Dac. If a usb dac is not connected, then the default audio out will be the analog jack. Nasty!

Now, we create our music directories and mount points. We can use multiple directories, such a nas and a usb drive, by putting a shortcut in mpd default music directory.

mkdir /mnt/nas
chmod 777 /mnt/nas

Add the following line in /etc/fstab

nano /etc/fstab

//192.168.1.NasIP/YourShareName /mnt/nas cifs username=pi,password=,uid=mpd,file_mode=0644,dir_mode=0755,iocharset=utf8,rsize=130048,wsize=4096 0 0

This will automatically mount our samba share on /mnt/nas.

Now we mount an usb drivE. Please note that it is preferrable to use a fat formatted drive, this uses less resources. This is quite important, considering the notorious usb problems.

See how the drive is called

sudo fdisk -l

in my case:
/dev/sda1

We create the music folder:

mkdir /media/music
chmod -R 777 /media/music
mount /dev/sda1 /media/music

Then we add this line to /etc/fstab

sudo nano /etc/fstab

/dev/sda1 /media/music vfat defaults 0 0

Ctrl+ X then, y
We now add a symlink into the default music directory, this will give us the possibility to store our music library on multiple locations. For example, we can have a part of our library on the nas and another one on a usb drive

cd /var/lib/mpd/music
sudo ln -s /mnt/nas
sudo ln -s /media/music

Installing wi-fi client:

sudo apt-get install wicd-curses

cd /var/lib/mpd/music/

Tweaking

This is a fine tuning of the Pi software echosystem, even if we cannot get rid (as for now) of the usb problems, we can still do something to improve general usb performance. Adding this line to:

sudo nano /etc/modprobe.d/alsa-base.conf

options snd-usb-audio nrpacks=1

This sounds really effective to my hears!

There’s another tweak that should fix the usb problems, you should add a line in the cmdline.txt. This line turns the usb into 1.1 mode. Please note that by doing so, both usb and ethernet performance in terms of transfer speed will be greatly reduced. This doesn’t work for me, as my Usb Dac doesn’t work with this mode. Feel free to try it, please report if it solves the problem with your dac. You can remove this tweak by deleting the added parameter.

sudo nano /boot/cmdline.txt

dwc_otg.speed=1

Next step is to set the Pi’s cpu to work always at its full power. This is due to the fact that mpd for an unknown reason doesn’t trigger the scaling governor to increase computing speed while in use. By enabling the “performance” option, we’ll be sure that mpd has the full power it deserves.
First, we check out which power management profile we have:

cat /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor
powersave

Ok, let’s put the Pi in performance mode:

sudo su
echo -n performance > /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Check again with previous command to see if it is effective.
Using hw, insted of plug and mmemu

nano /etc/asound.conf

cancel existing text and paste this

pcm.!default {
type hw
card 0
}

ctl.!default {
type hw
card 0
}

LAN TUNING

sudo nano /etc/sysctl.conf

add line

fs.inotify.max_user_watches = 524288

If you should have some problems, remove it. In my configuration I don’t have any problems, but sometimes they could occour depending on traffic and tcp tranfer size.

Adjust limit values of the audio group

First we add mpd to the audio group

sudo nano /etc/security/limits.conf

@audio - rtprio 99
@audio - memlock unlimited
@audio - nice -19

Then we set mpd to have the highest priority (niceness). We do so by adding a script that starts afer mpd that renices it to -20

sudo su
cd /etc/init.d
nano myruns

We put this in the script:

#! /bin/sh
# /etc/init.d/myruns
#
### BEGIN INIT INFO
# Provides: myruns
# Required-Start: $all
# Required-Stop: $mpd
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Renicing mpd
# Description: Being nice with music
### END INIT INFO
# Some things that run always
touch /var/lock/myruns

MAXTRIES=15
TRIES=0

# Carry out specific functions when asked to by the system
case "$1" in
start)
#
# mount music
#
renice -n -20 -p `pgrep mpd`
;;
stop)
echo "Exiting myruns"
;;
*)
echo "Usage: /etc/init.d/myruns {start|stop}"
exit 1
;;
esac

exit 0
Ctrl+ x then y

We then set this as script and we add it to the init.d boot sequence:

chmod 755 myruns
update-rc.d myruns defaults

NAS tuning

sudo nano /etc/fstab

adding line
uid=mpd,file_mode=0644,dir_mode=0755,iocharset=utf8,rsize=130048,wsize=4096

Now we selectively deactivate some process, so they don’t start up nad we’ll have less active processes.

sudo apt-get install rccconf
sudo rccconf

The services I disabled:

cron – scheduler
lightdm – graphic login manager
motd – message of the day for ssh
plymouth- graphic bootlogo
x11-common graphic interface

This broke somehow my ssh server, avoiding me to connect via ssh, so be aware of it. If this will happen you should have access to your pi via a monitor and a keyboard and reinstall sshd via those commands:

sudo apt-get remove openssh-client openssh-server
sudo apt-get install openssh-client openssh-server

Now, we proceed to remove everything we used to compile and several things more. In case we don’t think we’re going to recompile something again.

sudo apt-get remove autoconf automake autotools-dev binutils build-essential dpkg-dev g++ g++-4.6 gcc gcc-4.6 libglib2.0-dev libid3tag0-dev libsamplerate0-dev libstdc++6-4.6-dev make pkg-config git-core x11-common dbus-x11 libice6 libx11-6 libx11-data libx11-xcb1 libxext6 libxi6 libxmuu1 libxtst6 xauth xkb-data fonts-freefont-ttf

cd /home/pi
sudo rm -rf mpd

That’s all folks, shake and serve with ice!

L'articolo RaspyFi Rc2 – How it’s made and list of all the optimizations sembra essere il primo su RaspyFi.

-512 mb model b support (but 256 models should work as well)
-based on latest raspbian image (2012-12-16-wheezy-raspbian)
-XMOS Native support (Hiface 2 is reported to be working)
-less space used and less processes active (shrinked to minimum requirements to get mpd running)
-fits on 2gb sd carD
-fat32 disk ready out of the boX
-volume can be set from client (Erik, this is for you!!)
-usb tweakings
-general quality improvements
-hdmi & analog audio disabled (no bcm2835 kernel module loaded at boot)
-mpd has higher priority set

known issues:
-resampling always enabled to 44100 htrz

SSH

User: pi
password: raspberry

Download RaspyFi RC1

UPDATE YOUR DATABASE FOR FIRST USE!

It Works out of the box with most of USB Dacs! (supported natively by linux) It works also with XMOS Transports (Hiface 2 is reported to be working!)

This is no more based on moebius linux, it is instead based on latest raspbian (updated at 12\1\13). It is definetely sounding better and it features some under the hood tweaking that proved to be effective. It is ready out of the box to play your library from a FAT32 usb stick or self powered hard disk. (IF you need ntfs support you should mount it and then edit /etc/mpd.conf).
You can also play your music from a Nas, you should have a samba share called nas and edit /etc/fstab and change the ip with you’r nas ip:

sudo nano /etc/fstab

//192.168.1.YOURIPHERE/nas /mnt/nas cifs username=pi,password= 0 0

reboot and edit /etc/mpd.conf , removing the comment from nas and commenting Music

music_directory “/mnt/nas”
#music_directory “/media/Music”

(Quality-wise, the nas option is strongly suggested)

To enjoy the best quality your RaspyFi powered Pi can give you please use a quality psu, I found out that Xperia phones chargers are pretty well made and stable, if you have an Ipod\Ipad\Iphone charger this could be good as well!

And you’re ready to go! I’m already working on a Real Time version of RaspyFi, stay tuned!

L'articolo RaspyFi new release is out! sembra essere il primo su RaspyFi.

Hey,

I’m experiencing audio stutter while playing movies via the Raspberry Pi to the TV. I used to have the 1080p videos buffering all the time, but I fixed by switching my shares from Samba to NFS, using Hanewin NFS Server. That fixed all the buffering issues and makes the Pi read the shares much, much faster.

http://openelec.tv/forum/134-usage/40394-audio-stuttering

I’m also having problems with RaspyFI, when i comment out the line

format          ”44100:16:2″    # optional

in order to avoi resampling (you remember Audiophilia Hysterica obliges you to think resampling is evil??) I get audio stuttering, especially with flac with samplerate higher than redbook standards . I do really think this is related to an driver issue of the Soc controlling both ethernet and USB.

The main theory circulating on the net states that usb related issues (which can affect wi-fi dongles transfer, keyboard and mouse imputs etc etc) are due to some drivers problems which manifestates themselfs under heavy stress of usb\ethernet pathways, in conjunction and in some cases alone. More precisely there seems that there is some packet loss:

- USB congestion:our devices work in full-speed (USB 1.1 12 Mbit/s) and transmit at max 1 packet of 64 bytes each frame (64 Kb/s). We have analyse the transfer with and USB analyser and ALL packets are correctly transmitted over the wire (no bus reset, no invalid packet, the USB host ack all packet). this mean that the USB Host controller of the raspberry Pi as correctly received and ack the missing USB packet.Our conclusion is that or the libusb or the linux kernel drop some packets and do not raise any error.
We have found a serious issue on the raspberry PI USB stack (or at last the HID USB stack). We produce USB device and have found that we often get missing packet.
We have create an specific firmware illustrate the problem. This debug protocol is very simple the Raspberry will send one packet of 64 bytes, then the device will start a burst of USB transaction. Our USB device work in full speed (USB 1.1) and follow the HID protocol. All packets have the same size (64 bytes). the first uint32_t will contain the current packet number and the second uint32_t will contain the number of packet to send. Each packet is numbered and we stop after burst of 4096 packet of on the first missing packet.

The debug program call libusb-1.0, and will look for one of our device with the debug firmware, then send one USB packet to the device to start the burst. Then we will wait for all packet and check that all packet are send. You can download the source here http://www.yoctopuce.com/tmp/debug_libusb.zip

We have test this code and firmware on many linux platform (i386 and x86_64), and on a ARM based NAS (QNAP TS-219P II). We never get any missing packet. but on the Raspberry PI we always get missing packets. We have check with a USB analyser that the missing packet is correctly sent on the wire (the packet has been correctly acked by the Raspberry PI USB host). It seems that the packet is lost by the Raspberry PI firmware.

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=5249

In addition to this:

The USB driver may not be fixable, the jury is still out on this one. There are three key problems:

1) Documentation on the Broadcom USB controller is proprietary and is not made openly available by the Raspberry Pi Foundation.

2) The USB core for the Broadcom SoC was bought from a 3rd party, and we are told that not even Broadcom has full documentation, nor understands the driver.

3) The Foundation has discovered that the controller and its driver expect realtime response from the ARM core, and if Linux’s non-realtime scheduling doesn’t respond in 1 ms, a split transaction USB event can be dropped. Not surprisingly, this occurs regularly and produces lost mouse clicks, stuck keyboard keys, etc..

That’s a pretty nasty combination of problems, and it means that assuming that it’s fixable may not be a safe prediction. We’ll have to wait and see.

For the time being though, USB and networking (which is implemented over USB) have a large catalogue of issues and incompatibilities. All boards have this inherent problem but YMMV on whether the issues bite you, as it depends on exactly what devices you have connnected and what you’re doing with the board.

In addition to the above faults, the community discovered a PCB track layout error on the board which causes a proportion of the USB chips to overheat owing to an incorrect connection. It doesn’t appear to be critical but wastes power and the heat may shorten board or device lifetime.

Relations are very tense on the forum, and the Foundation has banned people who express their concern about the faults.

http://hardware.slashdot.org/story/12/08/24/2228251/serious-problems-with-usb-and-ethernet-on-the-raspberry-pi

 

So what happens? Under heavy load some of our precious binary vives is lost and never reaches our fancy USB Dac. Setting the resample mode seems to avoid it because of less bandwith is required to stream the audio to the dac, but we don’t want this as we are:

1- Applying some post processing to our audio stream (which, I remember should be evil to us…)
2- Making our hi-res flac library very sad
3- Degrading our listening experience as it is non-bit- perfect (wheter this is perceptible or not, still I don’t know… but we are damn audio purity integralists, aren’t we?)

But, is there a light out of the tunnel? Of course yes, theorethically at least.

As you can find out from that quote:

3) The Foundation has discovered that the controller and its driver expect realtime response from the ARM core, and if Linux’s non-realtime scheduling doesn’t respond in 1 ms, a split transaction USB event can be dropped. Not surprisingly, this occurs regularly and produces lost mouse clicks, stuck keyboard keys, etc..

 

So, if we succeed in compiling a real-time kernel, hopefully out problem will be solved and finally we’ll have bit perfect reproducion. This is already in process, as a superuser from tforumhifi il helping while compiling a custom real-time kernel for RaspyFi, you can follow the iter here on the RaspyFi thread:

http://www.tforumhifi.com/t32285-raspyfi-raspberry-pi-voyage-mpd-progetto-per-un-ottima-sorgente-low-cost

Meanwhile, a possible solution for audio stuttering via usb is made possible by setting the Usb transfer rate to USB 1.1 and setting it in full mode:

We have run some tests today to validate the tentative fixes.

First we have run rpi-update to get the latest fix. Here is my cmdline.txt and the kernel version

CODE: 

root@raspberrypi:/home/pi# more /boot/cmdline.txt
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
root@raspberrypi:/home/pi# uname -a
Linux raspberrypi 3.2.27+ #160 PREEMPT Mon Sep 17 23:18:42 BST 2012 armv6l GNU/Linux


As expected, Gordon fix does not completely solve the issue of packet loss in this case, but the packet loss seems to happen far less frequently (I have been able to stress the PI for several minutes before I get a missing packet).

Then we have added the dwc_otg.speed=1 parameter to force USB to work only in full speed mode (speed of USB 1.1). This solved the issue. This confirms that the PI has some trouble to handle USB 1.1 devices behind an USB 2.0 hub, but forcing the USB to work in full speed mode completely solves the packet loss for our USB 1.1 devices.

Our working config:

CODE: 

root@raspberrypi:/home/pi# more /boot/cmdline.txt
dwc_otg.lpm_enable=0 console=ttyAMA0,115200 kgdboc=ttyAMA0,115200 dwc_otg.speed=
1 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait
root@raspberrypi:/home/pi# uname -a
Linux raspberrypi 3.2.27+ 

http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=5249&start=200

This is done byadding the dwc_otg.speed=1 parameter to force USB to work only in full speed mode:

sudo nano /boot/cmdline.txt

and adding dwc_otg.speed=1 in the text. ctrl +x, y and reboot

adding the dwc_otg.speed=1 parameter to force USB to work only in full speed mode

Some reported this solution as working, It’s worth trying… I’ll let you know…

Then a final option is this, that prevents kernel panic by setting always free quote of memory and setting the Soc in turbo mode.

Just to report, I had exactly the same error and I solved with:

• vm.min_free_kbytes = 32768 in /etc/sysctl.conf
• smsc95xx.turbo_mode=N in /boot/cmdline.txt

Remember that with turbo mode enabled you are seriously risking to corrupt your SD card…

So, that’s all about USB problems with the PI, I’ll upgrade this post with new informations when they’ll come out.

L'articolo Anatomy of a PI – USB Audio quality and related issues on Pi sembra essere il primo su RaspyFi.