Linux-audio-dev

linux-audio-dev@lists.linuxaudio.org

7516 discussions

by Duncan Gray

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.

14 years, 5 months

[LAA] [ANN] Release of aj-snapshot-0.9.4

by Lieven Moors

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

14 years, 5 months

Begining of work at flowcanvas replacement

by Nikita Zlobin

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).

14 years, 5 months

aj-snapshot fails to connect a2jmidid ports

by Lieven Moors

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

14 years, 5 months

EBU loudness meter

by Fons Adriaensen

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

14 years, 6 months

[OT] DAH PhD Programme, scholarships available

by Victor Lazzarini

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

14 years, 6 months

ANN: Upcoming L2Ork tour of Europe

by Ivica Ico Bukvic

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 21 - Hamburg, Germany (Academy of Music and Theater) May 24 - 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/

14 years, 6 months

LAC 2011: Sunday night

by Egor Sanin

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.

14 years, 6 months

Linux Audio Conference 2011 starts today with live video stream coverage

by Jörn Nettingsmeier

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

14 years, 6 months

[LAC] [LAC] Kilcar B&B

by Egor Sanin

Hello LACers! I've got myself into a mixup. I've booked a hostel in Dublin for the Conference, but now I want to get out to Maynooth. I've been in touch with Kilcar B&B and Annette has me covered for Friday night, however, after that she's full. I remember someone here was asking about teaming up for a place, so perhaps there's a chance someone over there is willing to split a room and costs. If you don't mind a roommate, please email or call me. I'm in Dublin right now at Avalon house. I've got a mobile here: 085 7836111. I will be walking around a lot today, so phone is better. Thanks gang, I'm looking forward to meeting everyone!

14 years, 6 months

Jump to page:

2025

2024

2023

2022

2021

2020

2019

2018

2017

2016

2015

2014

2013

2012

2011

2010

2009

2008

2007

2006

2005

2004

2003

2002

Linux-audio-dev