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• Revisiting Nosefart and Discovering GME

  30 mai 2011, par Multimedia Mike — Game Hacking

  I found the following screenshot buried deep in an old directory structure of mine :

  
  
  

  I tried to recall how this screenshot came to exist. Had I actually created a functional KDE frontend to Nosefart yet neglected to release it ? I think it’s more likely that I used some designer tool (possibly KDevelop) to prototype a frontend. This would have been sometime in 2000.

  However, this screenshot prompted me to revisit Nosefart.

  Nosefart Background
  Nosefart is a program that can play Nintendo Sound Format (NSF) files. NSF files are files containing components that were surgically separated from Nintendo Entertainment System (NES) ROM dumps. These components contain the music playback engines for various games. An NSF player is a stripped down emulation system that can simulate the NES6502 CPU along with the custom hardware (2 square waves, 1 triangle wave, 1 noise generator, and 1 limited digital channel).

  Nosefart was written by Matt Conte and eventually imported into a Sourceforge project, though it has not seen any development since then. The distribution contains standalone command line players for Linux and DOS, a GTK frontend for the Linux command line version, and plugins for Winamp, XMMS, and CL-Amp.

  The Sourceforge project page notes that Nosefart is also part of XBMC. Let the record show that Nosefart is also incorporated into xine (I did that in 2002, I think).

  Upgrading the API
  When I tried running the command line version of Nosefart under Linux, I hit hard against the legacy audio API : OSS. Remember that ?

  In fairly short order, I was able to upgrade the CL program to use PulseAudio. The program is not especially sophisticated. It’s a single-threaded affair which checks for a keypress, processes an audio frame, and sends the frame out to the OSS file interface. All that was needed was to rewrite open_hardware() and close_hardware() for PA and then replace the write statement in play(). The only quirk that stood out is that including <pulse/pulseaudio.h> is insufficient for programming PA’s simple API. <pulse/simple.h> must be included separately.

  For extra credit, I adapted the program to ALSA. The program uses the most simplistic audio output API possible — just keep filling a buffer and sending it out to the DAC.

  Discovering GME
  I’m not sure what to do with the the program now since, during my research to attempt to bring Nosefart up to date, I became aware of a software library named Game Music Emu, or GME. It’s a pure C++ library that can essentially play any classic video game format you can possible name. Wow. A lot can happen in 10 years when you’re not paying attention.

  It’s such a well-written library that I didn’t need any tutorial or documentation to come up to speed. Just a quick read of the main gme.h header library enabled me in short order to whip up a quick C program that could play NSF and SPC files. Path of least resistance : Client program asks library to open a hardcoded file, synthesize 10 seconds of audio, and dump it into a file ; ask the FLAC command line program to transcode raw data to .flac file ; use ffplay to verify the results.

  I might develop some other uses for this library.

• How to restrict ffmpeg to use only 50% of my CPU ?

  21 septembre 2016, par zukes

  i m using ffmpeg for streaming my desktop over UDP but my problem is ffmpeg’s process always takes 100% cpu for the entire time it is running leaving no room other application , my question is how can i restrict ffmpeg’s process to take up only 50-60% of cpu ?

  My cpu has single core
  2 gb ram

• Creating thumbnails with FFmpeg

  3 janvier 2012, par Calin-Andrei Burloiu

  I am using FFmpeg to extract thumbnails from specific positions of video files.

  I found on the web two approaches to do this :

  1. With -ss (seek) parameter before -i (input) parameter :

     ffmpeg -y -ss $SEEK_POINT -i input.ogv -vcodec mjpeg -vframes 1 -an -s 120x90 -f rawvideo output.jpg

  2. With -ss (seek) parameter after -i (input) parameter :

     ffmpeg -y -i input.ogv -vcodec mjpeg -ss $SEEK_POINT -vframes 1 -an -s 120x90 -f rawvideo output.jpg

  The first method generates a bad thumbnail with gray spots, but works very fast. The error returned is [theora @ 0x8097240] vp3: first frame not a keyframe.

  The second method always works but show an error which cause the extraction to take a lot of time. This amount of time is not fixed and it depends on the seek point as I noticed. Sometimes it takes a few seconds and other times several minutes to extract a thumbnail. I get the error Buffering several frames is not supported. Please consume all available frames before adding a new one. in the following output :

  Input #0, ogg, from 'input.ogv':
  
    Duration: 00:21:52.76, start: 0.000000, bitrate: 844 kb/s
  
      Stream #0.0: Video: theora, yuv420p, 800x600 [PAR 4:3 DAR 16:9], 25 fps, 25 tbr, 25 tbn, 25 tbc
  
      Stream #0.1: Audio: vorbis, 44100 Hz, stereo, s16, 192 kb/s
  
      Metadata:
  
        ENCODER         : Lavf52.102.0
  
  Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selecting format 'yuvj420p'                                                                         
  
  [buffer @ 0x9250840] w:800 h:600 pixfmt:yuv420p                                 
  
  [scale @ 0x92508a0] w:800 h:600 fmt:yuv420p -> w:120 h:90 fmt:yuvj420p flags:0x4
  
  Output #0, rawvideo, to 'output.jpg':
  
    Metadata:
  
      encoder         : Lavf53.2.0
  
      Stream #0.0: Video: mjpeg, yuvj420p, 120x90 [PAR 4:3 DAR 16:9], q=2-31, 200 kb/s, 90k tbn, 25 tbc
  
  Stream mapping:
  
    Stream #0.0 -> #0.0
  
  Press ctrl-c to stop encoding
  
  [buffer @ 0x9250840] Buffering several frames is not supported. Please consume all available frames before adding a new one.                                    
  
  frame=    0 fps=  0 q=0.0 size=       0kB time=10000000000.00 bitrate=   0.0kbit
  
  Last message repeated 15448 times
  
  frame=    1 fps=  0 q=3.4 Lsize=       3kB time=0.04 bitrate= 598.8kbits/s    
  
  video:3kB audio:0kB global headers:0kB muxing overhead 0.000000%

  How can I extract thumbnails without any problems using FFmpeg from a custom position of a video regardless of the input format ?