Recherche avancée

Sur d’autres sites (7312)

• Adding C64 SID Music

  1er novembre 2012, par Multimedia Mike — General

  I have been working on adding support for SID files — the music format for the Commodore 64 — to the game music website for awhile. I feel a bit out of my element since I’m not that familiar with the C64. But why should I let that slow me down ? Allow me to go through the steps I have previously outlined in order to make this happen.

  
  
  

  I need to know what picture should represent the system in the search results page. The foregoing picture should be fine, but I’m getting way ahead of myself.

  Phase 1 is finding adequate player software. The most venerable contender in this arena is libsidplay, or so I first thought. It turns out that there’s libsidplay (originally hosted at Geocities, apparently, and no longer on the net) and also libsidplay2. Both are kind of old (libsidplay2 was last updated in 2004). I tried to compile libsidplay2 and the C++ didn’t agree with current version of g++.

  However, a recent effort named libsidplayfp is carrying on the SID emulation tradition. It works rather well, notwithstanding the fact that compiling the entire library has a habit of apparently hanging the Linux VM where I develop this stuff.

  Phase 2 is to develop a testbench app around the playback library. With the help of the libsidplayfp library maintainers, I accomplished this. The testbench app consistently requires about 15% of a single core of a fairly powerful Core i7. So I look forward to recommendations that I port that playback library to pure JavaScript.

  Phase 3 is plug into the web player. I haven’t worked on this yet. I’m confident that this will work since phase 2 worked (plus, I have a plan to combine phases 2 and 3).

  One interesting issue that has arisen is that proper operation of libsidplayfp requires that 3 C64 ROM files be present (the, ahem, KERNAL, BASIC interpreter, and character generator). While these are copyrighted ROMs, they are easily obtainable on the internet. The goal of my project is to eliminate as much friction as possible for enjoying these old tunes. To that end, I will just bake the ROM files directly into the player.

  Phase 4 is collecting a SID song corpus. This is the simplest part of the whole process thanks to the remarkable curation efforts of the High Voltage SID Collection (HVSC). Anyone can download a giant archive of every known SID file. So that’s a done deal.

  Or is it ? One small issue is that I was hoping that the first iteration of my game music website would focus on, well, game music. There is a lot of music in the HVSC that are original compositions or come from demos. The way that the archive is organized makes it difficult to automatically discern whether a particular SID file comes from a game or not.

  Phase 5 is munging the metadata. The good news here is that the files have the metadata built in. The not-so-great news is that there isn’t quite as much as I might like. Each file is tagged with title, author, and publisher/copyright. If there is more than one song in a file, they all have the same metadata. Fortunately, if I can import them all into my game music database, there is an opportunity to add a lot more metadata.

  Further, there is no play length metadata for these files. This means I will need to set each to a default length like 2 minutes and do something like I did before in order to automatically determine if any songs terminate sooner.

  Oddly, the issue I’m most concerned about is character encoding. This is the first project for which I’m making certain that I understand character encoding since I can’t reasonably get away with assuming that everything is ASCII. So far, based on the random sampling of SID files I have checked, there is a good chance of encountering metadata strings with characters that are not in the lower ASCII set. From what I have observed, these characters map to Unicode code points. So I finally get to learn about manipulating strings in such a way that it preserves the character encoding. At the very least, I need Python to rip the strings out of the binary SID files and make sure the Unicode remains intact while being inserted into an SQLite3 database.

• FFMPEG : Invalid Pixel Format String -1 when converting MP3 to SWF

  22 janvier 2013, par James Riley

  I'm having an issue with FFMPEG - receiving an error when trying to convert an MP3 into an SWF. The full output contains :

  $ ffmpeg -i track1.mp3 -y -ar '44100' -ab '96k' 'sample.swf'
  
      FFmpeg version SVN-r26402, Copyright (c) 2000-2011 the FFmpeg developers
  
      configuration: --enable-libmp3lame --enable-libvorbis --enable-shared --disable-mmx
  
      libavutil     50.36. 0 / 50.36. 0
  
      libavcore      0.16. 1 /  0.16. 1
  
      libavcodec    52.108. 0 / 52.108. 0
  
      libavformat   52.93. 0 / 52.93. 0
  
      libavdevice   52. 2. 3 / 52. 2. 3
  
      libavfilter    1.74. 0 /  1.74. 0
  
      libswscale     0.12. 0 /  0.12. 0
  
      Input #0, nsv, from 'track1.mp3':
  
       Metadata:
  
         encoder         : Lavf52.93.0
  
         artist          : Test
  
         title           : Track02
  
         album           : Mixtape
  
         disc            : 1/1
  
         genre           : Acoustic
  
         date            : 2013
  
         track           : 2/2
  
         album_artist    : Test
  
         Duration: 00:00:00.00, start: 0.000000, bitrate: -2147483 kb/s
  
         Stream #0.0: Video: [216][195]2[138] / 0x8A32C3D8, 44318x50468, 24 fps, 24 tbr, 24 tbn, 24 tbc
  
         Stream #0.1: Audio: h[228][146][142] / 0x8E92E468, 0 channels
  
      [buffer @ 0x175cd00] Invalid pixel format string '-1'
  
      Error opening filters!

  I'm aware the FFmpeg version here is old, but the issue is only occuring for one of the MP3s I am testing here. I have many others that are working just fine.

  What can be causing this issue and what steps can I take to resolve this ?

  From what I understand, the pixel format relates to the video output, yet in this case, the SWF is only to be used for audio. I've tested this on a newer version of FFmpeg and the issue isn't occuring - I certainly plan to upgrade FFmpeg on the test server I'm using, but would like to get to the bottom of why this is happening and try to get this particular MP3 converting, where its currently failing despite many others not having the same issue.

  Thanks for any help !

• Breaking a video into frames with python

  30 juillet 2012, par user1481112

  I am trying to write a program that deletes frames of a video that don't have a particular symbol in them. My general plan :

  1. Split the audio from the video
  2. Split the video into frames
  3. Run the frames through a subroutine that looks for the symbol, by checking the pixels where it should be for being the correct color, and logging the ones that don't.
  4. Delete those frames and corresponding audio seconds
  5. Splices it all back together.

  I need some help finding libraries that can do this. I was wondering if wxpython could do the detection of pixel color. I have no idea what library could split audio and video and which could edit audio. I know ffmpeg could split the video into frames but after two days of work I still have not been able to install it for python 2.7, so I either need a way to install it or a different library to do it. Any ideas ?