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• 2011 In Open Source Multimedia

  5 janvier 2012, par Multimedia Mike — Open Source Multimedia

  Sometimes I think that the pace of multimedia technology is slowing down. Obviously, I’m not paying close enough attention. I thought I would do a little 2011 year-end review of what happened in the world of open source multimedia, mainly for my own benefit. Let me know in the comments what I missed.

  The Split
  The biggest deal in open source multimedia was the matter of the project split. Where once stood one project (FFmpeg) there now stands two (also Libav). Where do things stand with the projects now ? Still very separate but similar. Both projects obsessively monitor each other’s git commits and prodigiously poach each other’s work, both projects being LGPL and all. Most features that land in one code base end up in the other. Thus, I refer to FFmpeg and Libav collectively as “the projects”.

  Some philosophical reasons for the split included project stagnation and development process friction. Curiously, these problems are fond memories now and the spirit of competition has pushed development forward at a blinding pace.

  People inside the project have strong opinions about the split ; that’s understandable. People outside the project have strong opinions about the split ; that’s somewhat less understandable, but whatever. After 5 years of working for Adobe on the Flash Player (a.k.a. the most hated software in all existence if internet nerds are to be believed on the matter), I’m so over internet nerd drama.

  For my part, I just try to maintain some appearance of neutrality since I manage some shared resources for the open source multimedia community (like the wiki and samples repo) and am trying to keep them from fracturing as well.

  Apple and Open Source
  It was big news that Apple magnanimously open sourced their lossless audio codec. That sets a great example and precedent.

  New Features
  I mined the 'git log' of the projects in order to pick out some features that were added during 2011.

  First off, Apple’s ProRes video codec was reverse engineered and incorporated into the multimedia libraries. And for some weird reason, this is an item that made the rounds in the geek press. I’m not entirely sure why, but it may have something to do with inter-project conflict. Anyway, here is the decoder in action, playing a video of some wild swine, one of the few samples we have :

  
  
  

  Other new video codecs included a reverse engineered Indeo 4 decoder. Gotta catch ‘em all ! That completes our collection of Indeo codecs. But that wasn’t enough– this year, we got a completely revised Indeo 3 decoder (the previous one, while functional, exhibited a lot of code artifacts betraying a direct ASM ->C translation). Oh, and many thanks to Kostya for this gem :

  
  
  

  That’s the new Origin Xan decoder (best known for Wing Commander IV cinematics) in action, something I first started reverse engineering back in 2002. Thanks to Kostya for picking up my slack yet again.

  Continuing with the codec section, there is a decoder for Adobe Flash Screen Video 2 — big congrats on this ! One of my jobs at Adobe was documenting this format to the outside world and I was afraid I could never quite make it clear enough to build a complete re-implementation. But the team came through.

  Let’s see, there are decoders for VBLE video, Ut Video, Windows Media Image (WMVP/WMP2), Bink audio version ‘b’, H.264 4:2:2 intra frames, and MxPEG video. There is a DPX image encoder, a Cirrus Logic AccuPak video encoder, and a v410 codec.

  How about some more game stuff ? The projects saw — at long last — an SMJPEG demuxer. This will finally allow usage and testing of the SMJPEG IMA ADPCM audio decoder I added about a decade ago. Funny story behind that– I was porting all of my decoders from xine which included the SMJPEG ADPCM. I just never quite got around to writing a corresponding demuxer. Thanks to Paul Mahol for taking care of that.

  Here’s a DFA playback system for a 1995 DOS CD-ROM title called Chronomaster. No format is too obscure, nor its encoded contents too cheesy :

  
  
  

  There’s now a demuxer for a format called XMV that was (is ?) prevalent on Xbox titles. Now the projects can handle FMV files from many Xbox games, such as Thrillville.

  
  
  

  The projects also gained the ability to play BMV files. I think this surfing wizard comes from Discworld II. It’s non-computer-generated animation at a strange resolution.

  
  
  

  More demuxers : xWMA, PlayStation Portable PMP format, and CRI ADX format ; muxer for OpenMG audio and LATM muxer/demuxer.

  One more thing : an AVX-optimized fast Fourier transform (FFT). If you have a machine that supports AVX, there’s no way you’ll even notice the speed increase of a few measly FFT calls for audio coding/decoding, but that’s hardly the point. The projects always use everything on offer for any CPU.

  Please make me aware of features that I missed in the list !

  Continuous Testing
  As a result of the split, each project has its own FATE server, one for FFmpeg and one for Libav. As of the new year, FFmpeg has just over 1000 tests while Libav had 965. This is one area where I’m obviously ecstatic to see competition. Some ad-hoc measurements on my part indicate that the total code coverage via the FATEs has not appreciably increased. But that’s a total percentage. Both the test count and the code count have been steadily rising.

  Google Summer of Code and Google Code-In
  Once again, the projects were allowed to participate in the Google Summer of Code as well as Google Code-In. I confess that I didn’t keep up with these too carefully (and Code-In is still in progress as of this writing). I do know that the project split occurred after FFmpeg had already been accepted for GSoC season 2011 and the admins were gracious enough to allow FFmpeg and Libav to allow both projects to participate in the same slot as long as they could both be mature about it.

  Happy New Year
  Let’s see what we can accomplish in 2012.

• Dreamcast Operating Systems

  16 septembre 2010, par Multimedia Mike — Sega Dreamcast

  The Sega Dreamcast was famously emblazoned with a logo proudly announcing that it was compatible with Windows CE :

  
  
  

  It’s quite confusing. The console certainly doesn’t boot into some version of Windows to launch games. Apparently, there was a special version of CE developed for the DC and game companies had the option to leverage it. I do recall that some game startup screens would similarly advertise Windows CE.

  Once the homebrew community got ahold of the device, the sky was the limit. I think NetBSD was the first alternative OS to support the Dreamcast. Meanwhile, I have recollections of DC Linux and LinuxDC projects along with more generic Linux-SH and SH-Linux projects.

  
  
  

  DC Evolution hosts a disc image available for download with an unofficial version of DC Linux, assembled by one Adrian O’Grady. I figured out how to burn the disc (burning DC discs is a blog post of its own) and got it working in the console.

  It’s possible to log in directly via the physical keyboard or through a serial terminal provided that you have a coder’s cable. That reminds me– my local Fry’s had a selection of USB-to-serial cables. I think this is another area that is sufficiently commoditized that just about any cable ought to work with Linux out of the box. Or maybe I’m just extrapolating from the experience of having the cheapest cable in the selection (made by io connect) plug and play with Linux.

  
  
  

  Look ! No messy converter box in the middle as in the Belkin case. The reason I went with this cable is that the packaging claimed it was capable of up to 500 Kbits/sec. Most of the cables advertised a max of 115200 bps. I distinctly recall being able to use the DC coder’s cable at 230400 bps a long time ago. Alas, 115200 seems to be the speed limit, even with this new USB cable.

  Anyway, the distribution is based on a 2.4.5 kernel circa 2001. I tried to make PPP work over the serial cable but the kernel doesn’t have support. If you’re interested, here is some basic information about the machine from Linux’s perspective, gleaned from some simple commands. This helps remind us of a simpler time when Linux was able to run comfortably on a computer with 16 MB of RAM.

  Debian GNU/Linux testing/unstable dreamcast ttsc/1
  dreamcast login : root
  
  Linux dreamcast 2.4.5 #27 Thu May 31 07:06:51 JST 2001 sh4 unknown
  Most of the programs included with the Debian GNU/Linux system are
  
  freely redistributable ; the exact distribution terms for each program
  
  are described in the individual files in /usr/share/doc/*/copyright
  Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
  
  permitted by applicable law.
  dreamcast : # uname -a
  
  Linux dreamcast 2.4.5 #27 Thu May 31 07:06:51 JST 2001 sh4 unknown
  dreamcast : # cat /proc/cpuinfo 
  
  cpu family : SH-4
  
  cache size : 8K-byte/16K-byte
  
  bogomips : 199.47
  Machine : dreamcast
  
  CPU clock : 200.00MHz
  
  Bus clock : 100.00MHz
  
  Peripheral module clock : 50.00MHz
  dreamcast : # top -b
   09:14:54 up 14 min,  1 user,  load average : 0.04, 0.03, 0.03
  
  15 processes : 14 sleeping, 1 running, 0 zombie, 0 stopped
  
  CPU states :   1.1% user,   5.8% system,   0.0% nice,  93.1% idle
  
  Mem :     14616K total,    11316K used,     3300K free,     2296K buffers
  
  Swap :        0K total,        0K used,        0K free,     5556K cached
    PID USER     PRI  NI  SIZE  RSS SHARE STAT %CPU %MEM   TIME COMMAND
  
    219 root      18   0  1072 1068   868 R     5.6  7.3   0:00 top
  
      1 root       9   0   596  596   512 S     0.0  4.0   0:01 init
  
      2 root       9   0     0    0     0 SW    0.0  0.0   0:00 keventd
  
      3 root       9   0     0    0     0 SW    0.0  0.0   0:00 kswapd
  
      4 root       9   0     0    0     0 SW    0.0  0.0   0:00 kreclaimd
  
      5 root       9   0     0    0     0 SW    0.0  0.0   0:00 bdflush
  
      6 root       9   0     0    0     0 SW    0.0  0.0   0:00 kupdated
  
      7 root       9   0     0    0     0 SW    0.0  0.0   0:00 kmapled
  
     39 root       9   0   900  900   668 S     0.0  6.1   0:00 devfsd
  
     91 root       8   0   652  652   556 S     0.0  4.4   0:00 pump
  
     96 daemon     9   0   524  524   420 S     0.0  3.5   0:00 portmap
  
    149 root       9   0   944  944   796 S     0.0  6.4   0:00 syslogd
  
    152 root       9   0   604  604   456 S     0.0  4.1   0:00 klogd
  
    187 root       9   0   540  540   456 S     0.0  3.6   0:00 getty
  
    201 root       9   0  1380 1376  1112 S     0.0  9.4   0:01 bash
  

  Note that at this point I had shutdown both gpm and inetd. The rest of the processes, save for bash, are default. The above stats only report about 14 MB of RAM ; where are the other 2 MB ?

  dreamcast : # df -h
  Filesystem            Size  Used Avail Use% Mounted on
  /dev/rd/1             2.0M  560k  1.4M  28% /
  

• Fetch frame count with ffmpeg

  19 avril 2016, par Hansl

  Does anyone know how to fetch the number of total frames from a video file using ffmpeg ? The render output of ffmpeg shows the current frame and I need the frame count to calculate the progress in percent.