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• Dreamcast Track Sizes

  1er mars 2015, par Multimedia Mike — Sega Dreamcast

  I’ve been playing around with Sega Dreamcast discs lately. Not playing the games on the DC discs, of course, just studying their structure. To review, the Sega Dreamcast game console used special optical discs named GD-ROMs, where the GD stands for “gigadisc”. They are capable of holding about 1 gigabyte of data.

  You know what’s weird about these discs ? Each one manages to actually store a gigabyte of data. Each disc has a CD portion and a GD portion. The CD portion occupies the first 45000 sectors and can be read in any standard CD drive. This area is divided between a brief data track and a brief (usually) audio track.

  The GD region starts at sector 45000. Sometimes, it’s just one humongous data track that consumes the entire GD region. More often, however, the data track is split between the first track and the last track in the region and there are 1 or more audio tracks in between. But the weird thing is, the GD region is always full. I made a study of it (click for a larger, interactive graph) :

  
  
  

  Some discs put special data or audio bonuses in the CD region for players to discover. But every disc manages to fill out the GD region. I checked up on a lot of those audio tracks that divide the GD data and they’re legitimate music tracks. So what’s the motivation ? Why would the data track be split in 2 pieces like that ?

  I eventually realized that I probably answered this question in this blog post from 4 years ago. The read speed from the outside of an optical disc is higher than the inside of the same disc. When I inspect the outer data tracks of some of these discs, sure enough, there seem to be timing-sensitive multimedia FMV files living on the outer stretches.

  One day, I’ll write a utility to take apart the split ISO-9660 filesystem offset from a weird sector.

• Call ffmpeg command from matlab (ubuntu 12.04)

  30 novembre 2014, par bigpig245

  I’m trying to call ffmpeg function to get duration of video from matlab. In command line, it returns ok :

  ntrang@ubuntu:~$ ffmpeg -i /home/ntrang/projects/dataset/hmdb51/01_test/a1.avi 2>&1 | sed -n "s/.*Duration: \([^,]*\), .*/\1/p"

  it returns 00:00:18.03

  But when I call it from matlab by system command :

  >> system('ffmpeg -i /home/ntrang/projects/dataset/hmdb51/01_test/a1.avi 2>&1 | sed -n "s/.*Duration: \([^,]*\), .*/\1/p"');

  it returns empty.

  This is my env setting in Matlab

  LD_LIBRARY_PATH='/usr/local/MATLAB/R2013a/sys/os/glnxa64:/usr/local/MATLAB/R2013a/bin/glnxa64:/usr/local/MATLAB/R2013a/extern/lib/glnxa64:/usr/local/MATLAB/R2013a/runtime/glnxa64:/usr/local/MATLAB/R2013a/sys/java/jre/glnxa64/jre/lib/amd64/native_threads:/usr/local/MATLAB/R2013a/sys/java/jre/glnxa64/jre/lib/amd64/server:/usr/local/MATLAB/R2013a/sys/java/jre/glnxa64/jre/lib/amd64'
  
  
  
  PATH='/usr/lib/lightdm/lightdm:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/lib/jvm/jdk1.7.0_51/bin'

  I also create symbolic link for libstdc but it can help nothing...

  I have looking around on Internet for solution but not so good so far... What should I do ?

  I’m using Matlab R2013a on Ubuntu 12.04.5 LTS 64bit...

  Thanks in advance.

• Linux - FFMpeg - Cannot open libmp3lame.so.0

  15 novembre 2014, par h4ng4r18

  I have installed FFMpeg to /bin/ffmpeg. When I try to run ffmpeg :

  ...bin]$ ffmpeg
  
  ffmpeg: error while loading shared libraries: libmp3lame.so.0: cannot open shared object file:
  
  No such file or directory

  however I can see this file

  bin]$ cd /usr/lib
  
  
  
  lib]$ dir
  
  cups        java-1.8.0        libavdevice.so.52      modprobe.d
  
  games       java-ext          libavdevice.so.52.2.3  python2.6
  
  gcc     jvm           libavformat.so.50      rpm
  
  java        jvm-commmon       libavformat.so.51      sendmail
  
  java-1.5.0  jvm-exports       libavutil.so.49        sendmail.sendmail
  
  java-1.6.0  jvm-private       libmp3lame.so.0        tmpfiles.d
  
  java-1.7.0  libavcodec.so.51  locale             yum-plugins

  I’m unsure of how to proceed at this stage - still quite new to Linux.

  The guide that I followed to get to this stage

  I am at the Symlinks stage and when I run

  sudo ln -s /usr/local/lib/libmp3lame.so.0 /usr/lib/libmp3lame.so.0

  I get "ln : failed to create symbolic link ‘/usr/lib/libmp3lame.so.0’ : File exists"