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• What Every Programmer Should Know

  24 décembre 2012, par Multimedia Mike — General

  During my recent effort to force myself to understand Unicode and modern text encoding/processing, I was reminded that this is something that “every programmer should just know”, an idea that comes up every so often, usually in relation to a subject in which the speaker is already an expert. One of the most absurd examples I ever witnessed was a blog post along the lines of “What every working programmer ought to know about [some very specific niche of enterprise-level Java programming]“. I remember reading through the article and recognizing that I had almost no knowledge of the material. Disturbing, since I am demonstrably a “working programmer”.

  For fun, I queried the googles on the matter of what ever programmer ought to know.

  Specific Topics
  Here is what every programmer should know about : Unicode, time, memory (simple), memory (extremely in-depth), regular expressions, search engine optimization, floating point, security, basic number theory, race conditions, managed C++, VIM commands, distributed systems, object-oriented design, latency numbers, rate monotonic algorithm, merging branches in Mercurial, classes of algorithms, and human names.

  Broader Topics
  20 subjects every programmer should know, 97 things every programmer should know, 12 things every programmer should know, things every programmer should know (27 items), 10 papers every programmer should read at least twice, 10 things every programmer should know for their first job.

  Meanwhile, I remain fond of this xkcd comic whose mouseover text describes all that a person genuinely needs to know. Still, the new year is upon us, a time when people often make commitments to bettering themselves, and it couldn’t hurt (much) to at least skim some of the lists and find out what you never knew that you never knew.

  What About Multimedia ?
  Reading the foregoing (or the titles of the foregoing pieces), I naturally wonder if I should write something about what every programmer should know about multimedia. I think it would look something like a multimedia programming FAQ. These are some items that I can think of :

  1. YUV : The other colorspace (since most programmers are only familiar with RGB and have no idea what to make of the YUV that comes out of most video decoding APIs)
  2. Why you can’t easily seek randomly to any specific frame in a video file (keyframe/interframe discussion and their implications)
  3. Understand your platform before endeavoring to implement multimedia software (modern platforms, particularly mobile platforms, probably provide everything you need in the native APIs and there is likely little reason to compile libavcodec for the platform)
  4. Difference between containers and codecs (longstanding item, but I would argue it’s less relevant these days due to standardization on the MPEG — MP4/H.264/AAC — stack)
  5. What counts as a multimedia standard in this day and age (comparing the foregoing MPEG stack with the WebM/VP8/Vorbis stack)
  6. Trade-offs to consider when engineering a multimedia solution
  7. Optimization doesn’t always work the way you think it does (not everything touted as a massive speed-up in the world of computing — whether it be multithreaded CPUs, GPGPUs, new SIMD instruction sets — will necessarily be applicable to multimedia processing)
  8. A practical guide to legal issues would not be amiss
  9.  ???

  What other items count as “something multimedia-related that every programmer should know” ?

• Death of A Micro Center

  21 septembre 2012, par Multimedia Mike — History

  The Micro Center computer store located in Santa Clara, CA, USA closed recently :

  
  
  

  I liked Micro Center. I have liked Micro Center ever since I first visited their Denver, CO location 10 years ago. I would sometimes drive an hour in each direction just to visit that shop. I was excited to see that they had a location in the Bay Area when I moved here a few years ago (despite the preponderance of Fry’s stores).

  Now this location is gone. I wonder how much of the “we couldn’t come to favorable terms on a lease” was true (vs. an excuse to close a retail store at a time when more business is moving online, particularly in the heart of Silicon Valley). But that’s not what I wanted to discuss. I came here to discuss…

  The Micro Center Window Logos

  The craziest part about shopping the Santa Clara Micro Center location was the logos they displayed on the window outside. Every time I saw it, it made me sentimental for a time when some of these logos were current, or when some of these companies were still in business. Some of the logos on their front window were for companies I’ve never heard of. It reminds me of the nearby 7-11 convenience stores when I was growing up– their walls were decorated with people sporting embarrassingly 1970s styles long after the 1970s had transpired.

  I thought I would record what those front window logos were and try to pinpoint when the store launched exactly (assuming the logos have been their since the initial opening and never changed).

  
  
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  Here we have Lotus, Hewlett Packard/HP, Corel, Fuji, Power Macintosh, NEC, and Fujitsu. Lotus was purchased by IBM in 1995 and still seems to be maintained as a separate brand. The Power Macintosh was introduced as a brand in 1994. Corel’s logo has seen a few mutations over the years but I don’t know when this one fell out of favor.

  Fuji (vs. Fujitsu) appears to refer to Fujifilm, though this logo is also obsolete.

  
  
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  Hayes– I specifically remember reading the Slashdot post accouncing that Hayes is dead (followed by many comments reminiscing about the Hayes command set). Here is the post, from early 1999.

  From Googling, it doesn’t appear IBM still has a presence in the consumer computing space (though they do have something pertaining to software for consumer products). Then there’s the good old rainbow Apple logo, something that went away in 1997. I suspect 1997 was also the last hurrah of the name ‘Macintosh’ (though I remember mistakenly referring to Apple computer products as Macintoshes well into the mid-2000s and inadvertently angering some Apple enthusiasts).

  
  
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  As for the next segment, obviously, both Sony and Toshiba are still very much alive. Iomega was acquired by EMC in 2008 but is still maintained as a separate brand. USRobotics is still around and making — what else ? — 56K modems (and their current logo is slightly different than the one seen here).

  Targus seems to be a case maker (“Leading Provider of Cases, Bags and Accessories for Laptops and Tablets”). I wonder if that’s just their current business or if they had more areas long ago ? It seems strange that they would get brand billing like this.

  Finally, searching for information about Practical Peripherals only produces sites about how they’re long dead (like this history lesson). It’s unclear when they died.

  The interior of this store was also decorated with more technology company logos near the ceiling (I didn’t really register that fact until I had visited many times). Regrettably, I now won’t be able to see how up to date those logos were.

  Based on the data points above, it’s safe to conclude that the store opened between 1995 or 1996 (again, assuming the logos were placed at opening and never changed).

  Epilogue

  Here’s one more curious item still visible from the outside :

  
  
  

  “See the world’s fastest PC !” Featuring an Intel Core 2 Extreme ? That CPU dates back to 2007 and was succeeded by Nehalem in late 2008. So even that sign, which is presumably easier and cleaner to replace than the window logos, was absurdly out of date.

• What is “interoperable TTML” ?

  19 septembre 2012, par silvia

  I’ve just tried to come to terms with the latest state of TTML, the Timed Text Markup Language.

  TTML has been specified by the W3C Timed Text Working Group and released as a RECommendation v1.0 in November 2010. Since then, several organisations have tried to adopt it as their caption file format. This includes the SMPTE, the EBU (European Broadcasting Union), and Microsoft.

  Both, Microsoft and the EBU actually looked at TTML in detail and decided that in order to make it usable for their use cases, a restriction of its functionalities is needed.

  EBU-TT

  The EBU released EBU-TT, which restricts the set of valid attributes and feature. “The EBU-TT format is intended to constrain the features provided by TTML, especially to make EBU-TT more suitable for the use with broadcast video and web video applications.” (see EBU-TT).

  In addition, EBU-specific namespaces were introduce to extend TTML with EBU-specific data types, e.g. ebuttdt:frameRateMultiplierType or ebuttdt:smpteTimingType. Similarly, a bunch of metadata elements were introduced, e.g. ebuttm:documentMetadata, ebuttm:documentEbuttVersion, or ebuttm:documentIdentifier.

  The use of namespaces as an extensibility mechanism will ascertain that EBU-TT files continue to be valid TTML files. However, any vanilla TTML parser will not know what to do with these custom extensions and will drop them on the floor.

  Simple Delivery Profile

  With the intention to make TTML ready for “internet delivery of Captions originated in the United States”, Microsoft proposed a “Simple Delivery Profile for Closed Captions (US)” (see Simple Profile). The Simple Profile is also a restriction of TTML.

  Unfortunately, the Microsoft profile is not the same as the EBU-TT profile : for example, it contains the “set” element, which is not conformant in EBU-TT. Similarly, the supported style features are different, e.g. Simple Profile supports “display-region”, while EBU-TT does not. On the other hand, EBU-TT supports monospace, sans-serif and serif fonts, while the Simple profile does not.

  Thus files created for the Simple Delivery Profile will not work on players that expect EBU-TT and the reverse.

  Fortunately, the Simple Delivery Profile does not introduce any new namespaces and new features, so at least it is an explicit subpart of TTML and not both a restriction and extension like EBU-TT.

  SMPTE-TT

  SMPTE also created a version of the TTML standard called SMPTE-TT. SMPTE did not decide on a subset of TTML for their purposes – it was simply adopted as a complete set. “This Standard provides a framework for timed text to be supported for content delivered via broadband means,…” (see SMPTE-TT).

  However, SMPTE extended TTML in SMPTE-TT with an ability to store a binary blob with captions in another format. This allows using SMPTE-TT as a transport format for any caption format and is deemed to help with “backwards compatibility”.

  Now, instead of specifying a profile, SMPTE decided to define how to convert CEA-608 captions to SMPTE-TT. Even if it’s not called a “profile”, that’s actually what it is. It even has its own namespace : “m608 :”.

  Conclusion

  With all these different versions of TTML, I ask myself what a video player that claims support for TTML will do to get something working. The only chance it has is to implement all the extensions defined in all the different profiles. I pity the player that has to deal with a SMPTE-TT file that has a binary blob in it and is expected to be able to decode this.

  Now, what is a caption author supposed to do when creating TTML ? They obviously cannot expect all players to be able to play back all TTML versions. Should they create different files depending on what platform they are targeting, i.e. a EBU-TT version, a SMPTE-TT version, a vanilla TTML version, and a Simple Delivery Profile version ? Should they by throwing all the features of all the versions into one TTML file and hope that the players will pick out the right things that they require and drop the rest on the floor ?

  Maybe the best way to progress would be to make a list of the “safe” features : those features that every TTML profile supports. That may be the best way to get an “interoperable TTML” file. Here’s me hoping that this minimal set of features doesn’t just end up being the usual (starttime, endtime, text) triple.

  UPDATE :

  I just found out that UltraViolet have their own profile of SMPTE-TT called CFF-TT (see UltraViolet FAQ and spec). They are making some SMPTE-TT fields optional, but introduce a new @forcedDisplayMode attribute under their own namespace “cff :”.