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• avcodec/amfenc : Fix AV1 HDR metadata for delayed surfaces

  10 septembre 2024, par Cameron Gutman

  avcodec/amfenc : Fix AV1 HDR metadata for delayed surfaces
  AMF_VIDEO_ENCODER_AV1_INPUT_HDR_METADATA was set above in the normal
  
  input case but forgotten for the same in the delayed surface codepath.
  Signed-off-by : Cameron Gutman <aicommander@gmail.com>
  
  Signed-off-by : Dmitrii Ovchinnikov <ovchinnikov.dmitrii@gmail.com>
  

  • [DH] libavcodec/amfenc.c

• Adventures in Unicode

  29 novembre 2012, par Multimedia Mike — Programming, php, Python, sqlite3, unicode

  Tangential to multimedia hacking is proper metadata handling. Recently, I have gathered an interest in processing a large corpus of multimedia files which are likely to contain metadata strings which do not fall into the lower ASCII set. This is significant because the lower ASCII set intersects perfectly with my own programming comfort zone. Indeed, all of my programming life, I have insisted on covering my ears and loudly asserting “LA LA LA LA LA ! ALL TEXT EVERYWHERE IS ASCII !” I suspect I’m not alone in this.

  Thus, I took this as an opportunity to conquer my longstanding fear of Unicode. I developed a self-learning course comprised of a series of exercises which add up to this diagram :

  
  
  

  Part 1 : Understanding Text Encoding
  Python has regular strings by default and then it has Unicode strings. The latter are prefixed by the letter ‘u’. This is what ‘ö’ looks like encoded in each type.

  python

  < view plain text >

  1. >>> ’ö’, u’ö’
  2. (’\xc3\xb6’, u’\xf6’)

  A large part of my frustration with Unicode comes from Python yelling at me about UnicodeDecodeErrors and an inability to handle the number 0xc3 for some reason. This usually comes when I’m trying to wrap my head around an unrelated problem and don’t care to get sidetracked by text encoding issues. However, when I studied the above output, I finally understood where the 0xc3 comes from. I just didn’t understand what the encoding represents exactly.
  

  I can see from assorted tables that ‘ö’ is character 0xF6 in various encodings (in Unicode and Latin-1), so u’\xf6′ makes sense. But what does ‘\xc3\xb6′ mean ? It’s my style to excavate straight down to the lowest levels, and I wanted to understand exactly how characters are represented in memory. The UTF-8 encoding tables inform us that any Unicode code point above 0x7F but less than 0×800 will be encoded with 2 bytes :

   110xxxxx 10xxxxxx
  

  Applying this pattern to the \xc3\xb6 encoding :

              hex : 0xc3      0xb6
             bits : 11000011  10110110
   important bits : ---00011  —110110
        assembled : 00011110110
       code point : 0xf6
  

  I was elated when I drew that out and made the connection. Maybe I’m the last programmer to figure this stuff out. But I’m still happy that I actually understand those Python errors pertaining to the number 0xc3 and that I won’t have to apply canned solutions without understanding the core problem.

  I’m cheating on this part of this exercise just a little bit since the diagram implied that the Unicode text needs to come from a binary file. I’ll return to that in a bit. For now, I’ll just contrive the following Unicode string from the Python REPL :

  python

  < view plain text >

  1. >>> u = u’Üñìçôđé’
  2. >>> u
  3. u’\xdc\xf1\xec\xe7\xf4\u0111\xe9’

  Part 2 : From Python To SQLite3
  The next step is to see what happens when I use Python’s SQLite3 module to dump the string into a new database. Will the Unicode encoding be preserved on disk ? What will UTF-8 look like on disk anyway ?

  python

  < view plain text >

  1. >>> import sqlite3
  2. >>> conn = sqlite3.connect(’unicode.db’)
  3. >>> conn.execute("CREATE TABLE t (t text)")
  4. >>> conn.execute("INSERT INTO t VALUES (?)", (u, ))
  5. >>> conn.commit()
  6. >>> conn.close()

  Next, I manually view the resulting database file (unicode.db) using a hex editor and look for strings. Here we go :

  000007F0   02 29 C3 9C  C3 B1 C3 AC  C3 A7 C3 B4  C4 91 C3 A9
  

  Look at that ! It’s just like the \xc3\xf6 encoding we see in the regular Python strings.

  Part 3 : From SQLite3 To A Web Page Via PHP
  Finally, use PHP (love it or hate it, but it’s what’s most convenient on my hosting provider) to query the string from the database and display it on a web page, completing the outlined processing pipeline.

  php

  < view plain text >

  1. < ?php
  2. $dbh = new PDO("sqlite:unicode.db") ;
  3. foreach ($dbh->query("SELECT t from t") as $row) ;
  4. $unicode_string = $row[’t’] ;
  5.  ?>
  6.  
  7. <html>
  8. <head><meta http-equiv="Content-Type" content="text/html ; charset=utf-8"></meta></head>
  9. <body><h1>< ?=$unicode_string ?></h1></body>
  10. </html>

  I tested the foregoing PHP script on 3 separate browsers that I had handy (Firefox, Internet Explorer, and Chrome) :

  
  
  

  I’d say that counts as success ! It’s important to note that the “meta http-equiv” tag is absolutely necessary. Omit and see something like this :

  
  
  

  Since we know what the UTF-8 stream looks like, it’s pretty obvious how the mapping is operating here : 0xc3 and 0xc4 correspond to ‘Ã’ and ‘Ä’, respectively. This corresponds to an encoding named ISO/IEC 8859-1, a.k.a. Latin-1. Speaking of which…

  Part 4 : Converting Binary Data To Unicode
  At the start of the experiment, I was trying to extract metadata strings from these binary multimedia files and I noticed characters like our friend ‘ö’ from above. In the bytestream, this was represented simply with 0xf6. I mistakenly believed that this was the on-disk representation of UTF-8. Wrong. Turns out it’s Latin-1.

  However, I still need to solve the problem of transforming such strings into Unicode to be shoved through the pipeline diagrammed above. For this experiment, I created a 9-byte file with the Latin-1 string ‘Üñìçôdé’ couched by 0′s, to simulate yanking a string out of a binary file. Here’s unicode.file :

  00000000   00 DC F1 EC  E7 F4 64 E9  00         ......d..
  

  (Aside : this experiment uses plain ‘d’ since the ‘đ’ with a bar through it doesn’t occur in Latin-1 ; shows up all over the place in Vietnamese, at least.)

  I’ve been mashing around Python code via the REPL, trying to get this string into a Unicode-friendly format. This is a successful method but it’s probably not the best :

  python

  < view plain text >

  1. >>> import struct
  2. >>> f = open(’unicode.file’, ’r’).read()
  3. >>> u = u’’
  4. >>> for c in struct.unpack("B"*7, f[1 :8]) :
  5. ... u += unichr(c)
  6. ...
  7. >>> u
  8. u’\xdc\xf1\xec\xe7\xf4d\xe9’
  9. >>> print u
  10. Üñìçôdé

  Conclusion
  Dealing with text encoding matters reminds me of dealing with integer endian-ness concerns. When you’re just dealing with one system, you probably don’t need to think too much about it because the system is usually handling everything consistently underneath the covers.

  However, when the data leaves one system and will be interpreted by another system, that’s when a programmer needs to be cognizant of matters such as integer endianness or text encoding.

• Announcing Long Term Support in Piwik 2 – The analytics platform for your mission critical projects

  11 janvier 2016, par Matthieu Aubry — About, Development

  We are proud to announce our Long Term Support (LTS) for Piwik 2.X !

  Why Long Term Support (LTS) ?

  Part of our mission is to ready Piwik for the enterprise — and ready the enterprise for Piwik. Our fast release cycle and our ability to quickly innovate has served us well for the past seven years and has lead Piwik to being one of the most popular open source projects, used by over one million websites worldwide. But Piwik’s success today has also shown us that this fast release cycle is not suited for all users and customers. Like most large open source projects (such as Ubuntu, Firefox, Debian, Symfony, Node.js, etc.) at Piwik we now also offer a Long Term Support release which gives users the confidence that Piwik can be used for mission critical projects for months to come.

  What does LTS mean for Piwik ?

  For the duration of the LTS period, Piwik 2.X will continue to receive the following fixes :

  • Critical bugs causing data loss or data corruption.
  • Major and Critical security issues.

  Our goal is to offer you a Piwik LTS release that you can trust for all your mission critical projects.

  How long will Piwik 2.X be supported ?

  Piwik 2.X will be supported for at least 12 months after the initial release of Piwik 3.0.0.
  Piwik 3.0.0 is expected to be released in the second half of 2016.
  This means that Piwik 2.X will be supported at least until the second half of 2017.

  Which Piwik version is LTS ?

  The latest Piwik 2.16.X release is our Long Term Support version.

  How do I benefit from the LTS version ?

  To get the full benefits of Piwik LTS, please make sure you are using the latest LTS version. First, update to the latest Piwik 2.X version, then Configure Piwik to use the LTS release channel and then update to the latest LTS version.

  How do I configure Piwik to use the LTS version ?

  By default, Piwik will not use the LTS version. When you use the one-click update your Piwik instance will be updated to the very latest release : when Piwik 3.0.0 will be released, the one click update will update your instance to 3.0.0. It is however possible to configure your Piwik so that you will stay on Piwik 2.X and keep using the LTS Long Term Support version :

  • Login Piwik as the Super User,
  • Go to Settings > General > Update settings,
  • Under “Release channel” click “Latest stable 2.X Long Term Support version”, and click “Save”.
    

  How do I get professional Piwik Support ?

  If you need professional support for your Piwik service get in touch with the Piwik experts.

  ---

  For other questions, feedback or discussion, feel free to join our forums and comment on this LTS forum post.

  We wish you all a fantastic year 2016 !