Recherche avancée

Sur d’autres sites (4359)

• SNES Hardware Compression

  16 juin 2011, par Multimedia Mike — Game Hacking

  I was browsing the source code for some Super Nintendo Entertainment System (SNES) emulators recently. I learned some interesting things about compression hardware. I had previously uncovered one compression algorithm used in an SNES title but that was implemented in software.

  SNES game cartridges — being all hardware — were at liberty to expand the hardware capabilities of the base system by adding new processors. The most well-known of these processors was the Super FX which allows for basic polygon graphical rendering, powering such games as Star Fox. It was by no means the only such add-on processor, though. Here is a Wikipedia page of all the enhancement chips used in assorted SNES games. A number of them mention compression and so I delved into the emulators to find the details :

  • The Super FX is listed in Wikipedia vaguely as being able to decompress graphics. I see no reference to decompression in emulator source code.
  • DSP-3 emulation source code makes reference to LZ-type compression as well as tree/symbol decoding. I’m not sure if the latter is a component of the former. Wikipedia lists the chip as supporting "Shannon-Fano bitstream decompression."
  • Similar to Super FX, the SA-1 chip is listed in Wikipedia as having some compression capabilities. Again, either that’s not true or none of the games that use the chip (notably Super Mario RPG) make use of the feature.
  • The S-DD1 chip uses arithmetic and Golomb encoding for compressing graphics. Wikipedia refers to this as the ABS Lossless Entropy Algorithm. Googling for further details on that algorithm name yields no results, but I suspect it’s unrelated to anti-lock brakes. The algorithm is alleged to allow Star Ocean to smash 13 MB of graphics into a 4 MB cartridge ROM (largest size of an SNES cartridge).
  • The SPC7110 can decompress data using a combination of arithmetic coding and Z-curve/Morton curve reordering.

  No, I don’t plan to implement codecs for these schemes. But it’s always comforting to know that I could.

  Not directly a compression scheme, but still a curious item is the MSU1 concept put forth by the bsnes emulator. This is a hypothetical coprocessor implemented by bsnes that gives an emulated cartridge access to a 4 GB address space. What to do with all this space ? Allow for the playback of uncompressed PCM audio as well as uncompressed video at 240x144x256 colors @ 30 fps. According to the docs and the source code, the latter feature doesn’t appear to be implemented, though ; only the raw PCM playback.

• Anomalie #2332 (Nouveau) : Critère {id_parent} dans boucles RUBRIQUES

  15 septembre 2011, par marcimat -

  Hop, en ce moment (SPIP 3.0.0-alpha2 SVN [18529]) la page ?exec=plan est en erreur, il y a une récursion infinie sur les rubriques provenant du critère id_parent inopérant lorsqu’il est seul. Mettre dans prive/squelettes/inclure/plan-rubriques.html : id_parent=#ID_RUBRIQUE et tout rentre dans (...)

• How to create buffer for video streaming

  4 juin 2014, par John Simpson

  I am developing a Android video player that can play RTSP Stream. I use ffmpeg in jni part to get and decode RTSP Stream. For now, the player can play and then pause video stream. The next step is to create a buffer for the player so that when user pauses video, the player can still load video stream in the next several seconds.

  Is there any good documentation on how to create a buffer for video streaming in proper way ?

  My plan is to create a array of packets. When the array is full, the player calls

   av_read_pause();

  to stop buffering. When the array has spaces, the player will call

   av_read_play();

  to continue buffering. There is a read_thread for getting packets from the buffer and the decode the packets. The read_thread will stop (resume), when user pauses (resume) video.

  Can this plan work ?