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Sridhar Dhanapalan: Twitter posts: 2015-05-11 to 2015-05-17

Mon, 2015-05-18 00:27

David Rowe: Lower SNR limit of Digital Voice

Fri, 2015-05-15 15:30

I’m currently working on a Digital Voice (DV) mode that will work at negative SNRs. So I started thinking about where the theoretical limits are:

  1. Lets assume we have a really good rate 0.5 FEC code that approaches the Shannon Limit of perfectly correcting random bit errors up to a channel BER of 12%
  2. A real-world code this good requires a FEC frame size of 1000′s of bits which will mean long latency (seconds). Lets assume that’s OK.
  3. A large frame size with perfect error correction means we can use a really low bit rate speech codec that can analyse seconds of speech at a time and remove all sorts of redundant information (like silence). This will allow us to code more efficiently and lower the bit rate. Also, we only want speech quality just on the limits of intelligibility. So lets assume a 300 bit/s speech codec.
  4. Using rate 0.5 FEC that’s a bit rate over the channel of 600 bit/s.
  5. Lets assume QPSK on a AWGN channel. It’s possible to make a fading channel behave like a AWGN channel if we use diversity, e.g. a long code with interleaving (time diversity), or spread spectrum (frequency diversity).
  6. QPSK at around 12% BER requires an Eb/No of -1dB or an Es/No of Eb/No + 3 = 2dB. If the bit rate is 600 bit/s the QPSK symbol rate is 300 symbols/s

So we have SNR = Es/No – 10*log10(NoiseBW/SymbolRate) = 2 – 10*log10(3000/300) = -8dB. Untrained operators find SSB very hard to use beneath 6dB, however I imagine many Ham contacts (especially brief exchanges of callsigns and signal reports) are made well beneath that. DV at -8dB would be completely noise free, but of low quality (e.g. a little robotic) and high latency.

For VHF applications C/No is a more suitable measurement, this is a C/No = SNR – 10*log10(3000) = 26.7dBHz (FM is a very scratchy readability 5 at around 43dBHz). That’s roughly a 20dB (100 x) power improvement over FM!

Dave Hall: Leaking Information in Drupal URLs

Fri, 2015-05-15 06:30

Update: It turns out the DA was trolling. We all now know that DrupalCon North America 2017 will be in New Orleans. I've kept this post up as I believe the information about handling unpublished nodes is relevant. I have also learned that m4032404 is enabled by default in govCMS.

When a user doesn't have access to content in Drupal a 403 forbidden response is returned. This is the case out of the box for unpublished content. The problem with this is that sensitive information may be contained in the URL. A great example of this the DrupalCon site.

The way to avoid this is to use the m4032404 module which changes a 403 response to a 404. This simple module prevents your site leaking information via URLs.

AttachmentSize DrupalCon-Philadephia.png139.21 KB

Janet Hawtin: lifeless

Thu, 2015-05-14 18:29
in the grit and sunbaked red

you can imagine moonscapes,

endless hot dry emptiness



but the ants commute even on this hot sand

lizards patrol their freeways with quick tongues



improbable silvergrey leaves stand isolated

sand and sticks collecting under the windward edge of any plant.



at dusk the restless kangaroos cross the landscape

in the evenings there are yowls of dingoes

dense clouds of insects orbit the lights

dawn is patterned with tracks



and if it rains

a magician's bouquet

life explodes, instant spring packetmix

just add water.











Andrew Pollock: [tech] LWN Chrome extension published

Thu, 2015-05-14 15:26

I finally got around to finishing off and publishing the LWN Chrome extension that I wrote a couple of months ago.

I received one piece of feedback from someone who read my blog via Planet Debian, but didn't appear to email me from a usable email address, so I'll respond to the criticisms here.

I wrote a Chrome extension because I use Google Chrome. To the best of my knowledge, it will work with Chromium as well, but as I've never used it, I can't really say for sure. I've chosen to licence the source under the Apache Licence, and make it freely available. So the extension is available to anyone who cares to download the source and "side load" it, if they don't want to use the Chrome Web Store.

As for whether a userscript would have done the job, maybe, but I have no experience with them.

Basically, I had an itch, and I scratched it, for the browser I choose to use, and I also chose to share it freely.

Binh Nguyen: Keeping Songs Fresh

Thu, 2015-05-14 03:25
If you've been keeping an eye on this blog then you would have noticed that I've been dabbling in music production of late. This is part of something that I've been working on, on and off now while I've been learning more about the craft.

https://www.youtube.com/watch?v=heWeovQRtMA

This is a playlist that I've created to upload such things.

https://www.youtube.com/playlist?list=PL3nb0opSp1dZtkXVdw8ihwJGzC1PtJmwe

Clearly, the track sample outlined above is fairly early in it's inception but it gives you an idea of some of the stuff that I am likely to produce in future.

As to the purpose of this particular post, it's basically about how to keep a song fresh by altering various aspects of it. For instance, think about the following:
  • alter tempo (don't restrict yourself to a single tempo throughout. Listen to grid music specialists (such as 'Jeremy Ellis', https://www.youtube.com/watch?v=HdFlFxJFnfY) and finger drummers (such as 'Mad Zach', http://www.madzach.com/, https://www.youtube.com/results?search_query=mad+zach) and you'll see that the sound is a lot more natural re is a lot to be gained by not adhering to stringently to tr
  • change key/scales (if you're aware of enough music theory you'll be aware that by altering 'modes/scales' you can change the entire feel of songs through that alone. Also remember that in the world of artificial sounds such as that produced by synthesisers scales can sometimes mean very little. Just go by ear in such cases...)
  • alter instruments for the same section (it's astonishing how much variety in software and ourboard gear you can get. Even if you just work with free stuff you'll have more than enough to build quality songs). While we're at it, give each and every instrument a chance. An example of this 'Doctor Rockit' in 'Cafe De Flore', https://www.youtube.com/watch?v=LFDyalRZbfY
  • the human voice (even when re-modulated/synthesised) can completely alter the feel of a song. The timbre itself can sort of be reproduced by artificial means but not quite yet which means you lose out on a lot by rejecting it. Listen to 'Kayne West's' version of 'Harder, Better, Faster Stronger', https://www.youtube.com/watch?v=3CgkWmKJLuE as opposed to the original version and you'll understand what I mean, https://www.youtube.com/watch?v=GDpmVUEjagg
  • if you have difficulty in finding an vocalist try specific social networks for this such as, http://vocalizr.com/ and https://blend.io/
  • else just become really good with instruments such as 'Chicane' in 'Offshore', https://www.youtube.com/watch?v=ltpCS5P0zCw
  • alter phase/time between tracks (slight changes in phase can have quite a different effect)
  • alter notes and their sequence (sounds obvious but doesn't seem to be sound obvious at times particularly when listening to heaps of club/dance music).
  • which leads us to the following point, learn to improvise and harmonise. I grew up on a lot of RnB and Hip Hop but ended up brancing out. Without this basis you'll find it very difficult to make something that doesn't sound overly repetitive. Examples of great harmony include, 'Boyz II Men' in 'End of The Road', https://www.youtube.com/watch?v=zDKO6XYXioc, 'Four Seasons of Loneliness', https://www.youtube.com/watch?v=fUSOZAgl95A, and 'I'll Make Love to You', https://www.youtube.com/watch?v=fV8vB1BB2qc
  • play around with the usual effects mid sound such as envelopes, modulation, LFO's, phasing, flanging, etc... A good example of this is with 'Flume', https://www.youtube.com/watch?v=fpyDJWxCep8&list=PLfk_Bv3x7xZLaDTrnJwvsJwQD_qJ2PmZ-
  • use of polyrhythms. Can be a little bit confusing to work with but can also achieve good results, http://en.wikipedia.org/wiki/Polyrhythm
  • use of effects such as panning, reverb, delay, EQ, etc... (be careful though. If you plan on deploying to clubs remember that their systems are often monophonic so some of your work may be for nothing. Also, a lot of people's standard stereo systems just don't have the range/ability to be able to do what you may want.)
  • use of automation in order to change relative volume of tracks/instruments in relation to one another
  • production and mixing techniques such as side-chain ducking, parallel processing, etc... Note, that sometimes you can go overboard and it can lose a lot of it's body though
  • split, explode, change sequence, ghost, reverse MIDI sections and/or audio samples
  • 'layering' sounds by having instruments play the same MIDI notes/sequences
  • think about push/pull aspects when dealing with 'fills'. Hear this in parts of Groove Aramda's, 'Lovebox', https://www.youtube.com/watch?v=izMBLSEt16o
  • add random file samples/sounds into the mixture every once in a while. A good example and common user of this technique is 'Daft Punk' in 'Around the World', https://www.youtube.com/watch?v=7nApiS9UTvc
  • gradually build into sections. Keeps it sounding like a song rather than a bunch of clips that have been assembled together. Also, creates a sense of fluidity. An example of this is 'Bob Sinclair' in 'World, Hold On', https://www.youtube.com/watch?v=yzlE7w9wRQk
  • this takes me to my next point, take your time when it comes to building a song. I've been dealing with this problem constantly. It's not just a bunch of clips put together. It's like a story. It's composed of words, phrases, pages, and ultimately a book. Tell the story completely. An example of this is 'Tom Novy's' song ' Take It', https://www.youtube.com/watch?v=_8ddq2NsjjU
  • that said when pushing/pulling/building into different sections one technique you can use to add a bit of 'freshness' is just giving them a hint here and there before hitting them with the complete section
  • think about utilising the entire frequency range. I've heard heaps of songs just cramp their frequency range into too small a range and it ends up losing some expressiveness
  • think about extending notes in breakdowns. A good example of this is 'When the Light's Go Out' by 'Five, https://www.youtube.com/watch?v=mpdcKmaHk_s
  • good songs start with a solid base. Even if they aren't electronic they start with a solid base/beat and build there way up into something great. Listen to 'Kaskade's' song 'This Rhythm' for an example of this, https://www.youtube.com/watch?v=cGRiFhIeWHM as well 'Mousse T' in 'Horny', https://www.youtube.com/watch?v=mGkHc11kSKs
  • use silence to your advantage. If you're just starting out you think you need to just fill every single moment in time with sound. Silence in the right places can change the entire feel of that particular section
  • don't think that pure digital or analogue is best. Fusing the two can produce wonderful results even if they are emulated via software. An example of this is using 'saturation', 'distortion', whitenoise effects to cut through the artificial/pure nature of the sounds that would otherwise be on show
  • use different sounds as well as effects during section transition. A good example of this by 'Doctor Rockit' in 'Cafe De Flore', https://www.youtube.com/watch?v=LFDyalRZbfY
  • listen to heaps of different artists and read a lot. A lot of what I've learnt has actually been from 'Computer Music Magazine' (a lot of content is actually duplicated by other music magazine publishers and articles are often superficially updated by the magazine and re-published. You can save a bit of money by being watchful for these things, http://www.musicradar.com/computermusic). Don't limit yourself to keep yourself interested as well as your listeners interested
https://garyewer.wordpress.com/2014/05/02/5-ideas-for-keeping-your-songs-fresh/ https://garyewer.wordpress.com/2011/08/17/keeping-songs-fresh-and-the-predictability-factor/

Linux Users of Victoria (LUV) Announce: LUV Main June 2015 Meeting: Using deep mutational scanning to understand protein function / Drupal8 out of the box

Tue, 2015-05-12 15:29
Start: Jun 2 2015 19:00 End: Jun 2 2015 21:00 Start: Jun 2 2015 19:00 End: Jun 2 2015 21:00 Location: 

200 Victoria St. Carlton VIC 3053

Link:  http://luv.asn.au/meetings/map

Speakers:

• Alan Rubin: Using deep mutational scanning to understand protein function

• Donna Benjamin: Drupal8 out of the box

200 Victoria St. Carlton VIC 3053 (formerly the EPA building)

Before and/or after each meeting those who are interested are welcome to join other members for dinner. We are open to suggestions for a good place to eat near our venue. Maria's on Peel Street in North Melbourne is currently the most popular place to eat after meetings.

LUV would like to acknowledge Red Hat for their help in obtaining the venue and VPAC for hosting.

Linux Users of Victoria Inc. is an incorporated association, registration number A0040056C.

June 2, 2015 - 19:00

read more

James Purser: Tired but looking up

Mon, 2015-05-11 23:30

Ye gods I'm tired.

Mostly I think this is due to the prodigious amount of travel that I've been doing to Melbourne for work, which while interesting, has left me with very little time to get a handle on things that I want to do outside of work.

There is a light on the horizon though, it looks like the Melbourne sojourne is coming to an end, and that means that at the very least psychologically I can start looking at committing to doing things around Angry Beanie that I've been meaning to do for the past six months.

So here's a rundown of the tasks I've set myself.

Rebuild Angry Beanie website using Django. This is mostly an exercise in learning Django and python, both tools I've looked at before but never really had a project to get my teeth into both.

Restart production of For Science and Purser Explores The World. I've been trying to get this restarted all year, but the aforementioned Melbourne trips have really thrown a kink in things.

On the subject of PETW I'd love to hear any subjects that you'd like me to cover. I already have a list of topics I want to look at, but I'm always up for more.

Blog Catagories: angry beanie

Colin Charles: Upcoming opportunities to talk MySQL/MariaDB in May 2015

Mon, 2015-05-11 21:25

May is quickly shaping up to be a month filled with activity in the MySQL/MariaDB space. Just a quick note to talk about where I’ll be; looking forward to meet folk to talk shop. 

  1. The London MySQL Meetup GroupMay 13 2015 – organized by former colleague & friend Ivan Zoratti, we will be doing a wrap up of recent announcements at Percona Live Santa Clara, and I’ll be showing off some of the spiffy new features we are building into MariaDB 10. 
  2. MariaDB Roadshow London – May 19 2015 – I’m going to give an overview of our roadmap, and there will be many excellent talks by colleagues there. I believe MariaDB Corporation CEO Patrik Sallner and Stu Schmidt, President at Zend will also be there. Should be a fun filled day. 
  3. Internet Society (ISOC) Hong Kong World Internet Developer Summit – May 21-22 2015 – I’ll be giving a keynote about MariaDB and how we are trying to make it important Internet infrastructure as well as making it developer friendly. 
  4. O’Reilly Velocity 2015 – May 27-29 2015 – I will in 90 minutes attempt to give a tutorial to attendees (over a 100 have already pre-registered) an overview of MySQL High Availability options and what their choices are in 2015. Expect a lot of talk on replication improvements from both MySQL & MariaDB, Galera Cluster, as well as tools around the ecosystem. 

Related posts:

  1. Opportunities to talk MariaDB/MySQL in Manila, Philippines
  2. Upcoming MariaDB 10.0.7 will have more engines – mroonga, OQGRAPH
  3. Upcoming MariaDB/MySQL events: Tokyo, Buenos Aires

Gary Pendergast: Oh Hai

Mon, 2015-05-11 15:26

 

Rohan Victor Pendergast, born 18:33 on 10/5/15.

Boy and Bear seemed to be what got him moving, so here they are now.

(PS: Should you ever find yourself in such a position, I highly recommend finding a hospital that gives the parents champagne for having a babby on Mother’s Day.)