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Elephants Dream - Cover of the soundtrack
17 octobre 2011, par
Mis à jour : Octobre 2011
Langue : English
Type : Image
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Autres articles (111)
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Script d’installation automatique de MediaSPIP
25 avril 2011, parAfin de palier aux difficultés d’installation dues principalement aux dépendances logicielles coté serveur, un script d’installation "tout en un" en bash a été créé afin de faciliter cette étape sur un serveur doté d’une distribution Linux compatible.
Vous devez bénéficier d’un accès SSH à votre serveur et d’un compte "root" afin de l’utiliser, ce qui permettra d’installer les dépendances. Contactez votre hébergeur si vous ne disposez pas de cela.
La documentation de l’utilisation du script d’installation (...) -
MediaSPIP 0.1 Beta version
25 avril 2011, parMediaSPIP 0.1 beta is the first version of MediaSPIP proclaimed as "usable".
The zip file provided here only contains the sources of MediaSPIP in its standalone version.
To get a working installation, you must manually install all-software dependencies on the server.
If you want to use this archive for an installation in "farm mode", you will also need to proceed to other manual (...) -
Les formats acceptés
28 janvier 2010, parLes commandes suivantes permettent d’avoir des informations sur les formats et codecs gérés par l’installation local de ffmpeg :
ffmpeg -codecs ffmpeg -formats
Les format videos acceptés en entrée
Cette liste est non exhaustive, elle met en exergue les principaux formats utilisés : h264 : H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 m4v : raw MPEG-4 video format flv : Flash Video (FLV) / Sorenson Spark / Sorenson H.263 Theora wmv :
Les formats vidéos de sortie possibles
Dans un premier temps on (...)
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Multiprocess FATE Revisited
26 juin 2010, par Multimedia Mike — FATE Server, PythonI thought I had brainstormed a simple, elegant, multithreaded, deadlock-free refactoring for FATE in a previous post. However, I sort of glossed over the test ordering logic which I had not yet prototyped. The grim, possibly deadlock-afflicted reality is that the main thread needs to be notified as tests are completed. So, the main thread sends test specs through a queue to be executed by n tester threads and those threads send results to a results aggregator thread. Additionally, the results aggregator will need to send completed test IDs back to the main thread.
But when I step back and look at the graph, I can’t rationalize why there should be a separate results aggregator thread. That was added to cut down on deadlock possibilities since the main thread and the tester threads would not be waiting for data from each other. Now that I’ve come to terms with the fact that the main and the testers need to exchange data in realtime, I think I can safely eliminate the result thread. Adding more threads is not the best way to guard against race conditions and deadlocks. Ask xine.
I’m still hung up on the deadlock issue. I have these queues through which the threads communicate. At issue is the fact that they can cause a thread to block when inserting an item if the queue is "full". How full is full ? Immaterial ; seeking to answer such a question is not how you guard against race conditions. Rather, it seems to me that one side should be doing non-blocking queue operations.
This is how I’m planning to revise the logic in the main thread :
test_set = set of all tests to execute tests_pending = test_set tests_blocked = empty set tests_queue = multi-consumer queue to send test specs to tester threads results_queue = multi-producer queue through which tester threads send results while there are tests in tests_pending : pop a test from test_set if test depends on any tests that appear in tests_pending : add test to tests_blocked else : add test to tests_queue in a non-blocking manner if tests_queue is full, add test to tests_blocked
while there are results in the results_queue :
get a result from result_queue in non-blocking manner
remove the corresponding test from tests_pendingif tests_blocked is non-empty :
sleep for 1 second
test_set = tests_blocked
tests_blocked = empty set
else :
insert n shutdown signals, one from each threadgo to the top of the loop and repeat until there are no more tests
while there are results in the results_queue :
get a result from result_queue in a blocking mannerNot mentioned in the pseudocode (so it doesn’t get too verbose) is logic to check whether the retrieved test result is actually an end-of-thread signal. These are accounted and the whole test process is done when one is received for each thread.
On the tester thread side, it’s safe for them to do blocking test queue retrievals and blocking result queue insertions. The reason for the 1-second delay before resetting tests_blocked and looping again is because I want to guard against the situation where tests A and B are to be run, A depends of B running first, and while B is running (and happens to be a long encoding test), the main thread is spinning about, obsessively testing whether it’s time to insert A into the tests queue.
It all sounds just crazy enough to work. In fact, I coded it up and it does work, sort of. The queue gets blocked pretty quickly. Instead of sleeping, I decided it’s better to perform the put operation using a 1-second timeout.
Still, I’m paranoid about the precise operation of the IPC queue mechanism at work here. What happens if I try to stuff in a test spec that’s a bit too large ? Will the module take whatever I give it and serialize it through the queue as soon as it can ? I think an impromptu science project is in order.
big-queue.py :
PYTHON :-
# !/usr/bin/python
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import multiprocessing
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import Queue
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def f(q) :
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str = q.get()
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print "reader function got a string of %d characters" % (len(str))
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q = multiprocessing.Queue()
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p = multiprocessing.Process(target=f, args=(q,))
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p.start()
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try :
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q.put_nowait(’a’ * 100000000)
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except Queue.Full :
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print "queue full"
$ ./big-queue.py reader function got a string of 100000000 characters
Since 100 MB doesn’t even make it choke, FATE’s little test specs shouldn’t pose any difficulty.
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