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• Feeding a series of images to ffmpeg as each image is created [closed]

  5 février 2013, par Mark Schneider

  I'm trying to use ffmpeg to build a 1280x720 slide-show from a sequence of pictures and videos, but I have concerns about potential disk I/O bottleneck.

  I expect a typical slide-show to have about 50 pictures and 2-3 videos (10-15 seconds each at 30 fps). I would like to show each picture for 3-4 seconds (possibly with a
  Ken Burns effect) with a smooth 2 second crossfade between each set of pictures (or for pictures adjacent to videos - between the picture and the first/last frame of the video).

  Given about 50 pictures, the crossfades alone would amount to about 3,000 images (50 transitions x 2 secs/transition x 30 fps). And I suppose if I implement a Ken Burns effect during each picture's 3-4 second showing, I'd have to provide ffmpeg with individual images for each of those frames. (I'm writing a script in Ruby that will pull a list of images from a database and in turn call ImageMagick to create the individual images for each frame. As I understand it, the RMagick library interfaces with ImageMagick such that the output images come back as in-memory objects without needing to write to disk. FWIW, I'm developing in Windows 8 and will deploy to Heroku.)

  All of the slideshow examples I've found online feed ffmpeg a set of images which have already been created. However, in an effort to avoid waiting on considerable disk I/O, I'd like to feed each image to ffmpeg as the image is created rather than create them all in advance.

  Is there a way to send each image file to ffmpeg on the fly as the file is created in memory ?

• Impliment FFmpeg in app and use it for images to video

  20 janvier 2014, par DanM

  I need you help. I have downloaded FFmpeg from here : Link.

  Does ffmpeg4android link is already ready for use in my application or I need to follow the tutorial ​How to Build FFmpeg for Android ?

  After I downloaded it, how can I use it for creating video from images ? Can you please provide me some tutorial for this ?

• Long Overdue MediaWiki Upgrade

  5 février 2014, par Multimedia Mike — General

  What do I do ? What I do ? This library book is 42 years overdue !
  I admit that it’s mine, yet I can’t pay the fine,
  Should I turn it in or should I hide it again ?
  What do I do ? What do I do ?

  I internalized the forgoing paean to the perils of procrastination by Shel Silverstein in my formative years. It’s probably why I’ve never paid a single cent in late fees in my entire life.

  However, I have been woefully negligent as the steward of the MediaWiki software that drives the world famous MultimediaWiki, the internet’s central repository of obscure technical knowledge related to multimedia. It is currently running of version 1.6 software. The latest version is 1.22.

  The Story So Far
  According to my records, I first set up the wiki late in 2005. I don’t know which MediaWiki release I was using at the time. I probably conducted a few upgrades in the early days, but that went by the wayside perhaps in 2007. My web host stopped allowing shell access and the MediaWiki upgrade process pretty much requires running a PHP script from a command line. Upgrade time came around and I put off the project. Weeks turned into months turned into years until, according to some notes, the wiki abruptly stopped working in July, 2011. Suddenly, there were PHP errors about “Namespace” being a reserved word.

  While I finally laid out a plan to upgrade the wiki after all these years, I eventually found that the problem had been caused when my webhost upgraded from PHP 5.2 -> 5.3. I also learned of a small number of code changes that caused the problem to go away, thus kicking the can down the road once more.

  Then a new problem showed up last week. I think it might be related to a new version of PHP again. This time, a few other things on my site broke, and I learned that my webhost now allows me to select a PHP version to use (with the version then set to “auto”, which didn’t yield much information). Rolling back to an earlier version of PHP might have solved the problem easily.

  But NO ! I made the determination that this goes no further. I want this wiki upgraded.

  The Arduous Upgrade Path
  There are 2 general upgrade paths I can think of :
  

  1. Upgrade in place on the server
  2. Upgrade offline and put the site back on the server

  Approach #1 is problematic since I don’t have direct shell access, though I considered using something like PHP Shell. Approach #2 involves getting the entire set of wiki files and a backup of the MySQL tables. This is workable since I keep automated backups of these items anyway.

  In fairly short order, I was able to set up a working copy of the MultimediaWiki hosted on a local Linux machine. Now what’s the move ? The MediaWiki software I’m running is 1.6.10. The very latest, as of this upgrade project is 1.22.2. I suppose it’s way too much to hope that the software will upgrade cleanly from 1.6.x straight to 1.22.x, but I guess it’s worth a shot…

  HA ! No chance. Okay, next idea is to march through the various versions and upgrade each in turn. MediaWiki has all their historic releases online, all the way back to the 1.3 lineage. I decided that the latest of each lineage should upgrade cleanly from anything in the previous version of lineage. E.g., 1.6.10 should upgrade cleanly to 1.7.3 (last in the 1.7 series). This seemed to be a workable strategy. So I downloaded the latest of each series, unpacked, and copied all the wiki files over the working installation and ran ‘php update.php’ in the maintenance/ directory.

  The process is tedious and not without its obstacles. I consider this penance for my years of wiki neglect. First, I run into the “PHP Parse error : syntax error, unexpected T_NAMESPACE, expecting T_STRING” issue, the same that I saw years ago after the webhost transitioned from PHP 5.2 -> 5.3. I could solve this by editing assorted files and changing “Namespace” -> “MWNamespace” (which is what MediaWiki did by version 1.13). But I would prefer not to.

  Instead, I downloaded the source for PHP 5.2 and compiled it in a separate directory, then called ‘/path/to/php/5.2/bin/php update.php’. Problem solved.

  The next problem is that a bunch of the database update scripts are specifying “Type=InnoDB”. This isn’t supported by modern MySQL databases. Now, it’s “Engine=InnoDB”. A quick search & replace at the command line fixes this for 1.6.x… and 1.7.x… and 1.8 through 1.12. Finally, at 1.13, it was no longer necessary. As a bonus, at 1.13, I was able to test the installation since Namespace had been renamed to MWNamespace. I would later learn that the table type modifications probably could have been simplified in by changing “$wgDBmysql4 = true ;” to “$wgDBmysql5 = true ;” somewhere in LocalSettings.php.

  Command line upgrading worked smoothly up through 1.18 series when I got a new syntax error :

  <br />
PHP Fatal error:  Call to a member function addMessages() on a non-object in /mnt/sdb1/archive/wiki/extensions/Cite.php on line 68<br />

  Best I could do was comment out that line. I hope that doesn’t break anything important.

  In the home stretch, the very last transition (1.21 -> 1.22) failed :

  PHP Fatal error :  Cannot redeclare wfProfileIn() (previously declared in 
  /mnt/sdb1/archive/wiki/includes/profiler/Profiler.php:33) in 
  /mnt/sdb1/archive/wiki/includes/ProfilerStub.php on line 25
  

  Apparently, this problem arises occasionally since 1.18. I found a way around it thanks to this page : Deleted the file StartProfiler.php. Who am I to argue ?

  Upon completing the transition to 1.22, the wiki doesn’t look correct– the pictures aren’t showing up. The solution was to fix the temporary directory via LocalSettings.php.

  Back To Production
  Okay, it all works again ! Locally, that is. How to get it back to the server ? My first idea was that, knowing that this upgrade process can succeed, try stepping through the upgrade process again, but tell the update.php scripts to access the database tables on multimedia.cx. This seemed to be working for awhile, even though the database update phase often took 4-5 minutes. However, the transition from 1.8.5 -> 1.9.6 took 75 minutes and then timed out. According to my notes, “This isn’t going to work.”

  The new process :

  1. Dump the database tables from the local database.
  2. Create a new database remotely (melanson_wiki_ng).
  3. Dump the database table into melanson_wiki_ng.
  4. Move the index.php file out of the wiki files directory temporarily (or rename).
  5. Modify the LocalSettings.php to talk to the new database.
  6. Perform a lftp mirror operation in order to send all the files up to the server.
  7. Send the index.php file and hope beyond hope that everything magically works.

  And that’s the story of how the updated MultimediaWiki came back online. Despite the database dump file being over 110 MB, it only tool MySQL 1m45s to transmit it all to the remote server (let’s hear it for the ‘–compress’ option). For comparison, inserting the tables back into a fresh local database took 1m07s.

  When the MultimediaWiki was first live again, it loaded, but ever so slowly. This is when I finally looked into optimization and found that I was lacking any caching. So as a bonus, the MultimediaWiki should be much faster now.

  Going Forward
  For all I know, I did everything described here in the hardest way possible. But at least I got it done. Unless I learn of a better process, future upgrades will probably look similar to this.

  Additionally, I should probably take some time to figure out what new features are part of the standard MediaWiki distribution nowadays.