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• 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.

• Video Filters like Instagram and save in SDCARD

  7 mai 2018, par Harsh Bhavsar

  Color Channel Mixer (Info.)
  https://ffmpeg.org/ffmpeg-filters.html#colorchannelmixer

  I am trying to creating video filters using FFMpeg and OpenCV just like Instagram Video filters.
  So if I want to create Sepia Effect Then I have to use color channel mixer for that with RGBA values
  ex. colorchannelmixer=.393 :.769 :.189:0 :.349 :.686 :.168:0 :.272 :.534 :.131 (This code for Sepia Effect)
  Now I want to create more effects like Instagram. So need different color channel mixers for that
  How to create them ?

  Ref. — https://github.com/krazykira/VidEffects/wiki/Permanent-video-effects

  I got only 2 filters

  Sepia
  colorchannelmixer=.393 :.769 :.189:0 :.349 :.686 :.168:0 :.272 :.534 :.131

  Grayscale
  colorchannelmixer=.3 :.4 :.3:0 :.3 :.4 :.3:0 :.3 :.4 :.3

  I need more filters.

  private void initVideoRecorder(String path) { 
  
  try { 
  
  filter = new F FmpegFrameFilter("colorchannelmixer=.393:.769:.189:0:.349:.686:.168:0:.272:.534:.131", VIDEO_GRABBER.getImageWidth(), VIDEO_GRABBER.getImageHeight()); 
  
  videoRecorder = FFmpegFrameRecorder.createDefault(path, VIDEO_GRABBER.getImageWidth(), VIDEO_GRABBER.getImageHeight()); videoRecorder.start(); 
  
  } 
  
  catch (FrameRecorder.Exception e) { 
  
  e.printStackTrace(); 
  
  }
  
   }

• Compilation error when compiling libvpx for FFMPEG

  29 septembre 2014, par Flock Dawson

  I’m compiling FFMPEG on my 64bit Ubuntu 14 machine. Everything compiled well, except for the libvpx library, which keeps throwing errors :

  [AS] vp9/common/x86/vp9_subpixel_8t_ssse3.asm.o
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:856: warning: label alone on a line without a colon might be in error
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:897: warning: label alone on a line without a colon might be in error
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:970: warning: label alone on a line without a colon might be in error
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:1002: warning: label alone on a line without a colon might be in error
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:340: error: invalid combination of opcode and operands
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:457: error: invalid combination of opcode and operands
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:897: error: invalid combination of opcode and operands
  
  vp9/common/x86/vp9_subpixel_8t_ssse3.asm:1002: error: invalid combination of opcode and operands
  
  make[1]: *** [vp9/common/x86/vp9_subpixel_8t_ssse3.asm.o] Error 1
  
  make: *** [.DEFAULT] Error 2

  I followed this guide : https://trac.ffmpeg.org/wiki/CompilationGuide/Ubuntu
  I don’t know what this error means, but read somewhere that compiling libvpx with NASM is broken, but I don’t know how to compile it otherwise. Installing version 1.2 or 1.1 makes no difference whatsoever. Any ideas ?