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• Trouble with CoCCA Registry

  7 octobre 2012, par Multimedia Mike — General

  I’ve been rather despondent all week. People who see me daily could readily identify this fact. Unfortunately, the exact reason was difficult to adequately explain. The problems that nerds deal with…

  When A Domain Expires
  As a few people noticed, the multimedia.cx domain and all of it’s subdomains didn’t work this last week. The problem started on Monday, October 1. Whose fault ? Well, fundamentally, I neglected to renew the domain name in time. However, I prefer to place the blame on the .cx domain registrar, CoCCA Registry. You see, they have never developed the technology to email a domain holder with a notice that their domain is about to expire or has already expired.

  This domain is the only one I have ever held so I don’t have a lot of experience in this matter. I wondered if I was crazy for thinking it would be normal for a registrar to send an email or 2 with status updates about your domain. I get the impression from speaking with others that this is indeed normal. I have 3 different email addresses listed under my account at the registrar– 2 at multimedia.cx and a backup gmail account. I checked spam folders after this incident. Then I remembered that I have never received any email notifications from them (although password reset emails show up, so that part thankfully works). Also, their support emails are black holes.

  So, I guess the moral is : be wary of dealing with CoCCA Registry. However, they seem to be the only way to register domains under a wide variety of uncommon country codes.

  By Friday, the domain appeared to have been reinstated, even through the status was officially listed as “renewal-pending” according to the web-based management console. Eventually, as cached DNS results started to time out throughout the day, I started seeing subdomains come back. I excitedly used the ‘dig’ command to count down the seconds until gamemusic.multimedia.cx was accessible on the network I was on (the number after the domain name is the time-to-live or ‘TTL’ value) :

  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 3      IN      A       174.143.152.251
  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 2      IN      A       174.143.152.251
  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 1      IN      A       174.143.152.251
  $ dig +nocmd gamemusic.multimedia.cx +noall +answer
  gamemusic.multimedia.cx. 12962  IN      A       207.45.186.114
  

  Finally, today (Saturday), I received a receipt confirming that the domain has been renewed.

  8 Years Old
  Incidentally, happy eighth birthday to multimedia.cx. It was September, 2004 when I decided to branch out from a simple ISP-based web presence.

  People often ask why I went with the .cx TLD. When I decided I wanted a proper domain name 8 years ago, I found that multimedia.X was already taken for just about every TLD value of X. .cx was a notable exception and was distinctive enough (speaking of .X, though, I see that multimedia.xxx is still up for grabs as of this writing ; I imagine that would come with a whole other set of problems).

  It’s funny that tech nerds often rail against outsourcing too much — email, storage, computing power, web hosting — all to some type of cloud provider under the premise that it could easily be taken away. But this episode teaches me that even having your own domain name is no guarantee of a solid online presence.

  Meanwhile, I have taken proactive steps to avert this same situation from arising again :

  
  
  

  Barring a lack of automated emails from the registrar, I hope a Google Calendar reminder set up a month ahead of expiration will do the trick.

• Solving The XVD Puzzle

  15 avril 2012, par Multimedia Mike — General, multimedi archaeology, silicon valley, vg2, xvd, zygo

  I downloaded a multimedia file a long time ago (at least, I strongly suspected it was a multimedia file which is why I downloaded it). It went by the name of ‘lamborghini_850kbps.vg2′. I have had it in my collection for at least 7 years. I couldn’t remember where I found it. I downloaded it before it occurred to me to take notes about this sort of stuff.

  I found myself staring at the file again today and Googled the filename. This led me to a few Japanese sites which also contained working URLs for a few more .vg2 samples. Some other clues led me to a Russian language forum where someone had linked to a site that had Win32 codec modules that could process the files. The site was defunct but the Internet Archive Wayback Machine kept a copy for me, as well as copies of several more .vg2 samples from a defunct Japanese site previously involved with this codec.

  Sometimes this internet technology works really well. But I digress.

  Anyway, through all this, I finally found a clue : XVD. and wouldn’t you know, there is already a basic page on the MultimediaWiki describing the technology. In fact, while VG2 is a custom container, the MultimediaWiki states that the video component has a FourCC of VGMV, and there is already a file named VGMV.avi in the root V-codecs/ samples directory, something I vow to correct (that’s a big pet peeve of mine– putting samples in the root V-codecs/ or A-codecs/ directories).

  XVD… XVD… XVD… why does that sound so familiar ? Oh, of course ; there is a company named XVD and they have an office in the Bay Area which I have passed on numerous occasions, like this morning :

  
  <

  Someone originally connected with the multimedia technology in question operates a website which contains an unofficial history of the XVD tech. At first, I was wondering if the technology was completely defunct (and should therefore be open sourced). But if XVD’s solutions page (dated 2010) is to be believed, the technology is still in service, and purported to be better than H.264 and VC-1 : “The current generation of XVD video compression technology provides better video quality at any given data rate than standards-based codecs (H.264 or VC-1) with four times lower encoding complexity (when compared with H.264 Main Profile).”

  If they say so. For my part, I’m just happy that I have finally figured out what this lamborghini_850kbps.vg2 is so that I can properly catalog it on the samples site, which I have now done, along with other samples and various codecs modules.

  This episode reminds me that there’s a branch office of Zygo Corporation close to my home (though the headquarters are far, far away). The companies you see in Silicon Valley. Anyway, long-time open source multimedia hackers will no doubt recognize Zygo from the ZyGo FourCC & video codec transported in QuickTime files that was almost decode-able using an H.263 decoder.

  
  
  

  I may never learn what Zygo’s core competency actually is, but I will always remember their multimedia tech every time I run past their office.

• avformat/vobsub : fix several issues.

  29 septembre 2013, par Clément Bœsch

  avformat/vobsub : fix several issues.
  Here is an extract of fate-samples/sub/vobsub.idx, with an additional
  
  text at the end of each line to better identify each bitmap :
      timestamp : 00:04:55:445, filepos : 00001b000 Ace !
  
      timestamp : 00:05:00:049, filepos : 00001b800 Wake up, honey !
  
      timestamp : 00:05:02:018, filepos : 00001c800 I gotta go to work.
  
      timestamp : 00:05:02:035, filepos : 00001d000 < ???>
  
      timestamp : 00:05:04:203, filepos : 00001d800 Look after Clayton, okay ?
  
      timestamp : 00:05:05:947, filepos : 00001e800 I’ll be back tonight.
  
      timestamp : 00:05:07:957, filepos : 00001f800 Bye ! Love you.
  
      timestamp : 00:05:21:295, filepos : 000020800 Hey, Ace ! What’s up ?
  
      timestamp : 00:05:23:356, filepos : 000021800 Hey, how’s it going ?
  
      timestamp : 00:05:24:640, filepos : 000022800 Remember what today is ? The 3rd !
  
      timestamp : 00:05:27:193, filepos : 000023800 Look over there !
  
      timestamp : 00:05:28:369, filepos : 000024800 Where are they going ?
  
      timestamp : 00:05:28:361, filepos : 000025000 < ???>
  
      timestamp : 00:05:29:946, filepos : 000025800 Let’s go see.
  
      timestamp : 00:05:31:230, filepos : 000026000 I can’t, man. I got Clayton.
  Note the two "< ???>" : they are basically split subtitles (with the
  
  previous one), which the dvdsub decoder is now supposed to reconstruct
  
  with a previous commit. But also note that while the first chunk has
  
  increasing timestamps,
      timestamp : 00:05:02:018, filepos : 00001c800
  
      timestamp : 00:05:02:035, filepos : 00001d000
  ...it’s not the case of the second one (and this is not an exception in the
  
  original file) :
      timestamp : 00:05:28:369, filepos : 000024800
  
      timestamp : 00:05:28:361, filepos : 000025000
  For the dvdsub decoder, they need to be "filepos’ed" ordered, but the
  
  FFDemuxSubtitlesQueue is timestamps ordered, which is the reason of the
  
  introduction of a sub sort method in the context, to allow giving
  
  priority to the position, and then the timestamps. With that change, the
  
  dvdsub decoder get fed with ordered packets.
  Now the packet size estimation was also broken : the filepos differences
  
  in the vobsub index defines the full data read between two subtitles
  
  chunks, and it is necessary to take into account what is read by the
  
  mpegps_read_pes_header() function since the length returned by that
  
  function doesn’t count the size of the data it reads. This is fixed with
  
  the introduction of total_read, and old,new_pos. By doing this change,
  
  we can drop the unreliable len16 heuristic and simplify the whole loop.
  
  Note that mpegps_read_pes_header() often read more than one PES packet
  
  (typically in one call it can read 0x1ba and 0x1be chunk along with the
  
  relevant 0x1bd packet), which triggers the "total_read + pkt_size >
  
  psize" check. This is an expected behaviour, which could be avoided by
  
  having a more chunked version of mpegps_read_pes_header().
  The latest change is the extraction of each stream into its own
  
  subtitles queue. If we don’t do this, the maximum size for a subtitle
  
  chunk is broken, and the previous changes can not work. Having each
  
  stream in a different queue requires some little adjustments in the
  
  seek code of the demuxer.
  This commit is only meaningful as a whole change and can not be easily
  
  split. The FATE test changes because it uses the vobsub demuxer.
  

  • [DH] libavformat/mpeg.c
  • [DH] libavformat/subtitles.c
  • [DH] libavformat/subtitles.h
  • [DH] tests/ref/fate/sub2video