Heya,
The Linux Plumbers Conference 2011 is coming soon. Mark Brown and I are running
the Audio track at LPC, and we are looking for more proposals!
So, please consider submitting something if you haven't done so yet. We
are looking for all kinds of technical talks covering everything audio
plumbing related: audio drivers, audio APIs, sound servers, pro audio,
consumer audio. If you can propose something audio related -- like talks
on media controller routing, on audio for ASOC/Embedded, submit
something! If you care for low-latency audio, submit something. If you
care about the Linux audio stack in general, submit something.
LPC is probably the most relevant technical conference on the general
Linux platform, so be sure that if you want your project, your work,
your ideas to be heard then this is the right forum for everything
related to the Linux stack. And the Audio track covers everything in our
Audio Stack, regardless whether it is pro or consumer audio.
So, submit! submit! submit!
(And contrary to what the web site might suggest regarding deadlines
we'll still consider your submission, if you post it quickly!)
http://www.linuxplumbersconf.org/2011/
Lennart
--
Lennart Poettering - Red Hat, Inc.
This is to bring a discussion from the Jack Dev list to this more
appropriate forum as suggested by Arnold Krille.
First, I hear lots of people seemingly thinking that AVB (IEEE 1722) and
the IEEE 1588 version of Precision Timing Protocol can be done in the
kernel.
It cannot and it must not. They both need hardware assist. Period. A
timestamp is specified to be inserted based on the leading edge of the
header immediately after the preamble. If anyone ever makes some
neighboring equipment that has done these with the required precision,
then you will kill that clock network and there will be yet another good
reason not to bring Linux to the workplace.
The ONLY exception is that if the listener is a stream-to-disk system,
then the timestamp system can simply be ignored. Such a listener will
never turn on PTP, but that won't hurt, because it will just ask for the
1722 stream and the talker will spit it out without knowing that that
node doesn't play PTP.
The version of PTP that is used in AVB is from the 802.1AS
specification. The acronym PTP is now an ambiguous one that has at
least these two uses, and I have heard some other hardware-assisted
networked timing schemes called PTP.
IEEE 1588 specifies an epoch-based struct with 48 bits of seconds (This
gives 8.9 million years before a "y2k" hits IEEE 1588) and a 32-bit
number that specifies nano-seconds. the 802.1AS sub-spec also uses this
epoch-based timestamp.
PTP maintains one suite of transactions to keep itself timed. This is
blind to AVB.
AVB creates Word Clock timeframes using the PTP wall-clock that MUST be
made available to the 1722 layer. IF YOU HAVE PTP, then you can
synthesize predictive wallclocks using a buffer-full scheme in a
PTP-capable NIC. That NIC has to be configured to pay out the frames
per the 802.1Qav forwarding and scheduling spec. This is how streamers
will deliver streams that are well-timed, low-jitter streams. There are
fruit companies doing this as we speak with new NICs that have been
enabled from Broadcom and Marvell (and any host of others.)
It is possible to fake a GrandMaster clock using kernel-timed
calculations. The Best Master Clock Algorithm (BMCA) of a two-node
system will be forced to accept such a sloppy clock and the slave will
achieve lock, but with jitter that will fail a normally specified PTP
system. Noisy environment listeners will not hear this, but clean
listening will reveal the various artifacts of such jitter.
You can just make a leaky-bucket PLL at a receiver and use the DPLL
frequency to inform SRC. This hack will be un-noticed by the average
media-player person, but not by the critical listener.
When the 1722 timestamp is constructed, it is a complex assembly from
the 802.1AS timestamp. The 802.1AS timestamp is a two-part thing, as
specified above with its first part being simply seconds. This will not
roll over in the lifetime of Linux, our species or even our continents,
let alone a recording session. The second part is specified to roll
over at decimal one billion-1 = 999999999 = 0x 3B9ACBFF. The timestamp
in IEEE 1722 rolls over at unsigned long = 4294967295 = 0xFFFFFFFF,
which is 4.294967296 seconds. I apologize for quoting "weeks between
rollover" in the previous thread.
IEEE 1588 and IEEE 1722 are Ethernet-Only protocols, do not shoe-horn
them into IP.
I have heard lots of people say that AVB is just some thing for consumers.
go to http://grouper.ieee.org/groups/1722/ and hover over some of the
names to find where they work. It was, in fact, designed FIRST to very
easily accommodate Pro Audio:
Reliability.
Multiple-Node Synchronization without the need for Sample Rate Conversion.
Low-Jitter.
Unlimited (at least not limited by the protocol, only the bandwidth)
channel count.
And then it would be a trivial subset to get two - or 5.1, 7.1 any
surround count - channels to go from my CD player to any media player
over some LAN. (However, as of two autumns ago, they were still
kvetching over Wi-Fi.)
Finally, Yes, the CLOCK_REALTIME can be very simply pasted from a good
PTP instance.
Hi everybody,
I've just released aj-snapshot-0.9.4
Aj-snapshot is a command line utility to store/restore
ALSA and JACK connections to/from an XML file.
Changes in this release:
- Make the -a and -j flags work together as expected, when they are combined.
- Fixed bug where aj-snapshot would not restore connections to a2jmidid ports.
- Refactoring of ignore-clients code.
For more information:
http://aj-snapshot.sourceforge.net/
To clone the git repository:
git clone git://aj-snapshot.git.sourceforge.net/gitroot/aj-snapshot/aj-snapshot
I hope you enjoy...
lievenmoors
I began to work at modular, patchage-like graph (afaik, flowcanvas i
used not only for such things - project panner in ardour3 looks using
it too). This graph is based on goocanvas, driven by cairo.
Project page: http://repo.or.cz/w/gmodulargraph.git
(of course, it is just a git web interface :)
For now i implemented modules with ports and wires. Began to implement
connections. There is no library yet, it is implemented in standalone
test execuable.
Though project is called GModularGraph, some files need to be renamed
(i changed name, because it depends on project, which is not a gtk
part).
Unfortunally i will go to military service after several hours (need to
sleep yet :), so it would be nice, if someone clone it and help with
development (also there is ability to push anonimously into 'mob'
branch, thanks to repo.or.cz for this feature).
Hi, I just discovered that aj-snapshot fails to connect
a2jmidid ports that appear in jack midi.
I store connections by seperating the client and port name
from what jack_get_ports returns, and I restore connections by
concatenating those as port names again (with a seperating colon).
This seems to work with most clients, but not with a2jmidid.
Does anyone know what the problem might be?
Thanks,
lieven
Hello all,
The EBU-R128 loudness meter presented today at the LAC
is now available at
<http://kokkinizita.linuxaudio.org/linuxaudio/downloads>
The package contains the interactive meter, the command
line app to measure sound files, and both the paper and
the presentation slides.
Ciao,
--
FA
Dear all,
we have started a new postgraduate programme, the Digital Arts and
Humanities PhD, which offers a computer music strand.
The programme has a number of scholarships available and applications
are open now.
http://www.forasfeasa.ie/http://learndigitalhumanities.ie/courses/postgrad/digital-arts-and-humaniti…
Regards
Dr Victor Lazzarini
Senior Lecturer
Dept. of Music
NUI Maynooth Ireland
tel.: +353 1 708 3545
Victor dot Lazzarini AT nuim dot ie
Apologies for cross-posting.
After 8 months of planning, fund-raising a metric ton of greenbacks, and literally thousands of hours of hard work distributed across dozens of souls, Linux Laptop Orchestra (L2Ork) is truly excited to announce our maiden tour of Europe May 12 – June 1, 2011. Joining forces with our guest soloist Ron Coulter and our talented soprano l2orkist Aurora Martin, the ensemble will be touring 8 countries, performing and holding workshops in following locations:
May 14 – Linz, Austria (as part of LiWoLi festival)
May 15 – Ljubljana, Slovenia
May 16 – Budapest, Hungary
May 19 – Croatia
May 21Â -Â Hamburg, Germany (Academy of Music and Theater)
May 24Â -Â Amsterdam, Netherlands (STEIM)
May 25 – Amsterdam, Netherlands (Zaal 100)
May 26 – Utrecht, Netherlands (HKU)
May 30 – Paris, France (IRCAM)
June 01 – Oslo, Norway (NIME 2011)
Hope to see you at one of our upcoming destinations! In the meantime, to stay up-to-date with the latest developments join our facebook page (http://www.facebook.com/group.php?gid=117918141555131)
For additional info on L2Ork please visit http://l2ork.music.vt.edu
On a somewhat related note, L2Ork has also made another series of updates to the Linux-centric pd-l2ork variation of Pd which is also available on the L2Ork site together with a series of externals and abstractions. For additional info on pd-l2ork please visit http://l2ork.music.vt.edu/main/?page_id=56
Should you happen to have any questions, suggestions or concerns, please do not hesitate to contact me.
Best wishes,
Ivica Ico Bukvic, D.M.A.
Composition, Music Technology
Director, DISIS Interactive Sound & Intermedia Studio
Director, L2Ork Linux Laptop Orchestra
Assistant Co-Director, CCTAD
CHCI, CS, and Art (by courtesy)
Virginia Tech
Dept. of Music - 0240
Blacksburg, VA 24061
(540) 231-6139
(540) 231-5034 (fax)
ico(a)vt.edu
http://www.music.vt.edu/faculty/bukvic/
Hi LACers,
Is anyone driving in the direction of Dublin or, better yet, the
airport late Sunday night after the conference? I've got a flight
early monday morning and if you're headed in that direction, I would
be very happy to contribute some cash for a lift.
Thanks.
hi everyone!
just a quick reminder that lac 2011 is starting today at 10:00 utc+1,
hosted by NUI maynooth in ireland.
find the program at http://lac.linuxaudio.org/2011.
live streams will be available from streamer.stackingdwarves.net in ogg
theora format.
remote participants are invited to join us on irc for conference-related
chitchat and real-time feedback. at the end of each session, you will
get the chance to ask questions to the presenter, which will be relayed
to the crowd in maynooth by a local chat operator.
best,
jörn