MPD is not offering any audio output

eragefe

Hi dafart Yes the PCB accepts both the Raspberry Pi and the beaglebone black.
You have to attach one of them to the right part of the pcb and the I2S will be transferred to the DAC from the RPi/BBB headers The RPi/BBB ground and the DAC ground will be galvanic isolated from each other.
Due to its compatibility to both RPi and BBB we are not going to call it for a BB cape.
I really don’t want to comment other constructions but as I stated before any kind of ripple on the ground degrades always the sound quality. That’s for sure.
Yes you need a separate chip to reclock. That chip takes also care of the problem with clicks and pops when mpd starts and stops a track. (All of those arm computers are stopping the I2S clocks when you stop playing a track and start all over again when you start playing.)

As I understand it the next version of RuneOs will include the drivers for the HDMI chip. In that case you will automatically get the I2S signals on the BBB header. That’s the case with debian and angstrom distributions for the BBB today.

I will also try to explain why and how NOS in another posting.

BR G

eragefe

I probably misunderstood you when you asking if you need a separate chip for reclocking.
That chip is already implemented on the board.

dafart

Thanks eragefe for your explanation!

I'm really exited to see how BBB + runeaudio + i2s over HDMI headers will work out..
I don't think enabling the kernel modules and make mpd use the device will be a big problem, we we're not there yet. AFAIK the hifiberry device works (as a DAC) on the RPi with volumio and is capable of bitperfect transport.

Do you also plan on adding extra connectors (digital s/pdif / coax / usb) or do you plan to transport the i2s signal over HDMI?

I just found out that the NAD M51 has hdmi input connectivity and also supports i2s (not really sure if that's i2s over hdmi or over usb)
But if the combination of the BBB with i2s out over hdmi plays fine with an M51 (or any other receiver with hdmi / i2s input support and a DAC built in) than this will be a very potent hi quality / audiophile little media device.
ComPred to all other network streaming devices I've tried, (not so many but still) all those DLNA supporting streamers get really slow when browsing through BIG libraries. MPD is extremely quick and therefor highly potent (for me)
I have not tried NAD's own system (used in the M50 M52 combo) or meriadian sooloos like systems, but IU doubt if they are as fast and responsive as the mpd / mpod is right now..

Good luck!!

Daf

eragefe

Hi Daf
I feel that I have to explain a little bit more.
As we say here in Sweden one picture says more than thousand words.
So I made a drawing that explains how it is.
The CPU feeding the HDMI chip with I2S and the chip sends audio+video to the HDMI connector.
You actually are “steeling” the I2S before it reaches the HDMI chip and feeding the DAC.
So we actually don’t use I2S over HDMI but I2S directly from soc.

BR G

Attachments

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dafart

Hi eragefe

Thanks for explaining.

So the i2s signal is being transported over hdmi..

That will make it easy to connect to an a/v receiver (though it should support i2s), but when one wants to connect it to a DAC for "pure" audio purposes the available DAC's with HDMI input support are limited.. The NAD M51 is the only one I'm currently aware of..

Or are there hdmi -> coax adapters> Or will that decrease audio quality.

Cheers, daf

eragefe

Ok I did some tests yesterday with BBB and I2S.
With the HDMI driver loaded you can get the I2S signals from P9 pins 28 29 31 on BBB.
BUT it seems that every single track you play is being resampled to 48KHz.(NOT bit perfect)
That is not unusual on both windows and Linux but almost unusable for real high end.

I can also say that the I2S from the RPi header IS bit perfect. (I tested tracks on 44.1, 176.4 and 192KHz).

BR G

ACX

eragefe wroteBUT it seems that every single track you play is being resampled to 48KHz.(NOT bit perfect)

That would be a very bad news if confirmed...
I did a quick Google search, and most of the results were telling the same thing... but maybe there is some hope:
http://permalink.gmane.org/gmane.linux.ports.arm.omap/110104
In the code you can see this part:

+static unsigned int tda998x_hdmi_rates[] = {
+	32000,
+	44100,
+	48000,
+	88200,
+	96000,
+};

so it could be possible to get a bit perfect playback from HDMI I2S... at least up to 96000Hz.

dafart

Is the resampling an issue with alsa?

Hopefully there is a workaround!

Tia,

Daf

eragefe

No no It is not an alsa problem.
My measurements is done with an analog scope so I cant post pictures and as I said the same OS/alsa with RPi works fine.
That has nothing to do with the hardware or the OS. Once again I am not expert on software but I think the problem has to do with the driver I used in my setup when I did the measurements.
It will be easily solved. (It maybe already is).
My setup was
BBB/nelsons debian for bbb/(TI_BeagleBone_B - TI BeagleBone Black) card/MPD/Alsa.
and
RPi/raspbian/(HifiBerry DAC HiFi pcm5102a-hifi-0)/MPD/Alsa

BR G

Midnight

ACX wrote
eragefe wroteBUT it seems that every single track you play is being resampled to 48KHz.(NOT bit perfect)
That would be a very bad news if confirmed...
I did a quick Google search, and most of the results were telling the same thing... but maybe there is some hope:
http://permalink.gmane.org/gmane.linux.ports.arm.omap/110104
...
so it could be possible to get a bit perfect playback from HDMI I2S... at least up to 96000Hz.

But there is also this description (McASP is an acronym for Multichannel Audio Serial Port, a communication peripheral found in Texas Instruments family of digital signal processors):

McASP produces the bit clock for the i2s bus from
the masted clock by a simple divider and the available sample rates
depend on the used master clock frequency.

So the available sample rates depend on the used CPU frequency?

EDIT: The BBB does not support 44.1 kHz and it's multiples, see this: http://patchwork.ozlabs.org/patch/303984/

eragefe

Ok That explains a lot.

BR G

ChrisMmm

I read what was in the link in the previous post but I am afraid didn't understand the issue exactly.

Does this limitation mean we are unlikely to see bit-perfect on the BBB or does a driver need to be written to cater for this?

Volumio says it has I2S capability for BBB, I tried it and got music but one channel was distorting. I guess that it may have been re-sampled tho.

Have I2S working fine on the RPi (Picoreplayer and Squeezelite) but I would prefer using the BBB as it seems to be a better board for this purpose.

Cheers

Midnight

The link says:

The 44100 Hz sample-rate and it's multiples can not be supported on Beaglebone-Black because of limited clock-rate support.

and

As I mentioned earlier, that is a BBB HW limitation only, the code bellow is able to decide what rates are available based on the sysclk rate.

This means, as far as I understand, the Soc is able to do the other frequencies, but not on the BBB. The main clock on the BBB only allows 48 kHz and 96 kHz sampling rate. As most tracks usually are 44.1 kHz (CD quality) it is not possible to play them bit perfect. Best solution IMHO is using on of mpd's high quality sampling rate converters and 96 kHz output:

samplerate_converter <integer or prefix>
This specifies the libsamplerate converter to use. The supplied value should either be an integer or a prefix of the name of a converter. The default is "Fastest Sinc Interpolator".
At the time of this writing, the following converters are available:

Best Sinc Interpolator (0)
Band limited sinc interpolation, best quality, 97dB SNR, 96% BW.

Medium Sinc Interpolator (1)
Band limited sinc interpolation, medium quality, 97dB SNR, 90% BW.

Fastest Sinc Interpolator (2)
Band limited sinc interpolation, fastest, 97dB SNR, 80% BW.

ZOH Interpolator (3)
Zero order hold interpolator, very fast, very poor quality with audible distortions.

Linear Interpolator (4)
Linear interpolator, very fast, poor quality.

internal
Poor quality, no floating point operations. This is the default (and only choice) if MPD was compiled without libsamplerate.

BTW: if you have heavy distortions it also may be related to dmix on ARM platforms. Disabling dmix for a music player like this is generally a good idea.

glt

I wonder what is that "HW limitation" coming from. Any lowly processor can derive any clock frequency by doing some math on the reference (on-board) clock.

eragefe

I absolutely agree.
I have seen on the net various tests with 44.1 tracks on bbb there people claim that they achieved that patching the driver.

BR G

Midnight

I have no idea what hardware limitation may be there, I've just repeated what I've read on the link

But in fact the datasheet says that the transmit clock of the McASP is generated by a simple divider from a master clock. But in 5 minutes I could not figure out what the master clock is.
The datasheet is here: http://www.ti.com/product/am3358

Midnight

eragefe wroteI absolutely agree.
I have seen on the net various tests with 44.1 tracks on bbb there people claim that they achieved that patching the driver.

Could you point to a url? I'm interested

eragefe

It was here I started to look into bbb/I2S months ago.
http://www.element14.com/community/community/knode/single-board_computers/next-gen_beaglebone/blog/2013/07/06/bbb--building-a-dac#comment-30847

BR G

aleg

This evening I upgraded my new BBB to the latest Angstrom distro and installed RuneAudio.
Just like the original poster my USB-SPDIF converter doesn't show up in the list of audio devices in RuneGUI.
Just Null (test output) is shown.

aplay -l does show my device and also the generated mpd.conf shows my device, but it is not enabled according to mpd.conf.

Do I need to enable my device manually or is it turned off for a reason?
If to be done manually where does it need to be changed becaue the mpd.conf says it is an auto generated file.

Thank you for your assistance

Cheers

Aleg

Debug info:

###### System info ######
Linux version 3.12.6-2-ARCH (nobody@root-chroot-copy) (gcc version 4.7.2 (GCC) ) #1 SMP Mon Jan 6 12:59:03 MST 2014

system load:	0.16 0.05 0.06 1/84 1323

HW platform:	BeagleBone Black (04)

playerID:	04e982c18599446a162f6ba2f08b9e05a8


###### Audio backend ######
Advanced Linux Sound Architecture Driver Version k3.12.6-2-ARCH.

Card list: (/proc/asound/cards)
--------------------------------------------------
 0 [hiFace         ]: snd-usb-hiface - hiFace
                      hiFace at usb-musb-hdrc.1.auto-1

ALSA interface #0: (/proc/asound/card0/pcm0p/info)
--------------------------------------------------
card: 0
device: 0
subdevice: 0
stream: PLAYBACK
id: USB-SPDIF Audio
name: USB-SPDIF Audio
subname: subdevice #0
class: 0
subclass: 0
subdevices_count: 1
subdevices_avail: 1

ALSA interface #1: (/proc/asound/card1/pcm0p/info)
--------------------------------------------------

interface #0 stream status: (/proc/asound/card0/stream0)
--------------------------------------------------------
no stream present

interface #1 stream status: (/proc/asound/card1/stream0)
--------------------------------------------------------
no stream present


###### Kernel module snd_usb_audio settings ######

Module = "snd_usb_audio"

  Attributes:
    coresize            = "112254"
    initsize            = "0"
    initstate           = "live"
    refcnt              = "0"
    taint               = ""
    uevent              = 

  Parameters:
    autoclock           = "Y"
    device_setup        = "0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0"
    enable              = "Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y,Y"
    id                  = "(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null),(null)"
    ignore_ctl_error    = "N"
    index               = "0,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1"
    nrpacks             = "3"
    pid                 = "-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1"
    vid                 = "-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1"

  Sections:
    .ARM.exidx.exit.text= "0xbf140e94"
    .ARM.exidx.init.text= "0xbf140e8c"
    .ARM.exidx          = "0xbf143334"
    .ARM.extab          = "0xbf1432bc"
    .ARM.extab.init.text= "0xbf140e80"
    .bss                = "0xbf1471e4"
    .data               = "0xbf143898"
    .exit.text          = "0xbf13f19c"
    .gnu.linkonce.this_module= "0xbf147080"
    .init.text          = "0xbf150000"
    .note.gnu.build-id  = "0xbf143874"
    .rodata             = "0xbf13f1a8"
    .rodata.str1.1      = "0xbf140f2c"
    .strtab             = "0xbf155328"
    .symtab             = "0xbf150048"
    .text               = "0xbf133000"
    __param             = "0xbf140e9c"


###### Kernel optimization parameters ######

hardware platform:	BeagleBone Black
current orionprofile:	RuneAudio

kernel scheduler for mmcblk0:		[noop] deadline cfq 
/proc/sys/vm/swappiness:		0
/proc/sys/kernel/sched_latency_ns:	4500000


###### Filesystem mounts ######

rootfs / rootfs rw 0 0
/dev/root / ext4 rw,relatime,data=ordered 0 0
devtmpfs /dev devtmpfs rw,relatime,size=253580k,nr_inodes=63395,mode=755 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620 0 0
mqueue /dev/mqueue mqueue rw,relatime 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
systemd-1 /proc/sys/fs/binfmt_misc autofs rw,relatime,fd=27,pgrp=1,timeout=300,minproto=5,maxproto=5,direct 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
securityfs /sys/kernel/security securityfs rw,nosuid,nodev,noexec,relatime 0 0
tmpfs /sys/fs/cgroup tmpfs rw,nosuid,nodev,noexec,mode=755 0 0
cgroup /sys/fs/cgroup/systemd cgroup rw,nosuid,nodev,noexec,relatime,xattr,release_agent=/usr/lib/systemd/systemd-cgroups-agent,name=systemd 0 0
cgroup /sys/fs/cgroup/cpuset cgroup rw,nosuid,nodev,noexec,relatime,cpuset 0 0
cgroup /sys/fs/cgroup/cpu,cpuacct cgroup rw,nosuid,nodev,noexec,relatime,cpuacct,cpu 0 0
cgroup /sys/fs/cgroup/memory cgroup rw,nosuid,nodev,noexec,relatime,memory 0 0
cgroup /sys/fs/cgroup/devices cgroup rw,nosuid,nodev,noexec,relatime,devices 0 0
cgroup /sys/fs/cgroup/freezer cgroup rw,nosuid,nodev,noexec,relatime,freezer 0 0
cgroup /sys/fs/cgroup/net_cls cgroup rw,nosuid,nodev,noexec,relatime,net_cls 0 0
cgroup /sys/fs/cgroup/blkio cgroup rw,nosuid,nodev,noexec,relatime,blkio 0 0
cgroup /sys/fs/cgroup/perf_event cgroup rw,nosuid,nodev,noexec,relatime,perf_event 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
configfs /sys/kernel/config configfs rw,relatime 0 0
tmpfs /run tmpfs rw,nosuid,nodev,mode=755 0 0
tmpfs /tmp tmpfs rw 0 0
tmpfs /tmp tmpfs rw 0 0
/dev/root /var/tmp ext4 rw,relatime,data=ordered 0 0
//192.168.178.41/Klassiek /mnt/MPD/Klassiek cifs ro,relatime,vers=1.0,sec=ntlm,cache=strict,uid=45,forceuid,gid=45,forcegid,addr=192.168.178.41,file_mode=0755,dir_mode=0755,nounix,serverino,rsize=16384,wsize=16384,actimeo=1 0 0


###### mpd.conf ######

###################################
# Auto generated mpd.conf file
# please DO NOT edit it manually!
# Use RuneUI MPD config section
###################################

follow_outside_symlinks 	"yes"
follow_inside_symlinks 	"yes"
db_file 	"/var/lib/mpd/mpd.db"
log_file 	"/var/log/runeaudio/mpd.log"
pid_file 	"/var/run/mpd/pid"
music_directory 	"/mnt/MPD"
playlist_directory 	"/var/lib/mpd/playlists"
state_file 	"/var/lib/mpd/mpdstate"
user 	"mpd"
bind_to_address 	"any"
port 	"6600"
log_level 	"default"
zeroconf_enabled 	"yes"
zeroconf_name 	"runeaudio"
volume_normalization 	"no"
audio_buffer_size 	"512"
buffer_before_play 	"0%"
filesystem_charset 	"UTF-8"
id3v1_encoding 	"UTF-8"
gapless_mp3_playback 	"yes"
auto_update 	"no"
mixer_type 	"none"
group 	"audio"
max_connections "20"

decoder {
		plugin "ffmpeg"
		enabled "no"
}

input {
		plugin "curl"
}

audio_output {
enabled		"no"
type		"alsa"
name		"USB-Audio"
device		"hw:0,0"
dsd_usb		"yes"
}

audio_output {
enabled		"yes"
type		"null"
name		"Null"
}

Orion

aleg wroteThis evening I upgraded my new BBB to the latest Angstrom distro and installed RuneAudio.
Just like the original poster my USB-SPDIF converter doesn't show up in the list of audio devices in RuneGUI.
Just Null (test output) is shown.

Hi aleg,
I think that our init-routine is missing your audio device.
Try this mod at source code:

Edit the file /var/www/inc/player_lib.php at line 1134

if (wrk_checkStrSysfile('/proc/asound/cards','USB-Audio')) {

and change it (all in a single line!!):

if (wrk_checkStrSysfile('/proc/asound/cards','USB-Audio') OR wrk_checkStrSysfile('/proc/asound/cards','hiFace')) {

reboot your BBB.

Let me know if it works.

Ciao.

Simone

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