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• 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.

• Compiling ffmpeg with emscripten

  18 septembre 2018, par noel

  I’m trying to compile ffmpeg into javascript so that I can decode H264 video streams using node. The streams are H264 frames packed into RTP NALUs so any solution has to be able to accept H264 frames rather than a whole file name.

  I found the Broadway.js library, but I couldn’t get it working and it doesn’t handle P-frames which I need. I also found ffmpeg.js, but could get that to work and it needs a whole file not a stream. Likewise, fluent-ffmpeg doesn’t appear to support file streams ; all of the examples show a filename being passed to the constructor. So I decided to write my own API.

  I have been able to compile ffmpeg into one big js file, but I can’t use it like that. I want to write an API around ffmpeg and then expose those functions to JS. So it seems to me like I need to do the following :

  1. Compile ffmpeg components (avcodec, avutil, etc.) into llvm bitcode.
  2. Write a C wrapper that exposes the decoding functionality and uses EMSCRIPTEN_KEEPALIVE.
  3. Use emcc to compile the wrapper and link it to the bitcode created in step 1.

  I found WASM+ffmpeg, but it’s in Chinese and some of the steps aren’t clear. In particular there is this step :

  emcc web.c process.c ../lib/libavformat.bc ../lib/libavcodec.bc ../lib/libswscale.bc ../lib/libswresample.bc ../lib/libavutil.bc \

  I don’t understand how all the ffmpeg components get compiled into separate *.bc files. I followed the emmake commands in that article and I end up with one big .bc file.

  Does anyone know the steps to compile ffmpeg using emscripten so that I can expose some API to javascript ?

  Is there a better way (with decent documentation) to decode h264 video streams using node ?

• Piwik Mobile 2 for Android – Release Candidate

  6 novembre 2013, par thomas — Community

  Exciting news ! We are proud to announce the availability of the first release candidate of Piwik Mobile 2 for Android. Check out the videos here or learn more in the FAQ.

  Piwik Mobile Users : we need your feedback !

  We have been testing Piwik Mobile 2 extensively at present. Now is your time to help us to track down any bugs, or even suggest usability improvements before the upcoming release in a few weeks. We are really interested in your feedback !

  Download

  Piwik Mobile 2 RC 1 for Android 4+

  Known issues

  All known issues are Piwik related and most of them will be fixed in the Piwik 2.0 release :

  • Some visitors in Visitor Log might be skipped #4044 (fixed)
  • If you are using a report date like “Last 7″ or “Last 30″, the number of visits won’t be displayed in the “All Websites Dashboard” #4068
  • Sometimes an HTML entity is displayed in the visitor screen #3970 (fixed)
  • Evolution graph fails to load and returns stack trace for Actions.getPageUrls #3943 (fixed)
  • Date Range is not correct recognized under circumstances #3074 (fixed)