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• Adding AY Files To The Game Music Website

  1er décembre 2013, par Multimedia Mike — General

  For the first time since I launched the site in the summer of last year, I finally added support for new systems for my Game Music Appreciation site : A set of chiptune music files which bear the file extension AY. These files come from games that were on the ZX Spectrum and Amstrad CPC computer systems.

  
   
  

  Right now, there are over 650 ZX Spectrum games in the site while there are all of 20 Amstrad CPC games. The latter system seems a bit short-changed, but I read that a lot of Amstrad games were straight ports from the Spectrum anyway since the systems possessed assorted similarities. This might help explain the discrepancy.

  Technically
  The AY corpus has always been low hanging fruit due to the fact that the site already supports the format courtesy of the game-music-emu backend. The thing that blocked me was that I didn’t know much about these systems. I knew that there were 2 systems (and possibly more) that shared the same chiptune format. Apparently, these machines were big in Europe (I was only vaguely aware of them before I started this project).

  Both the Spectrum and the Amstrad used Zilog Z-80 CPUs for computing and created music using a General Instruments synthesizer chip designated AY-3-8912, hence the chiptune file extension AY. This has 3 channels similar to the C64 SID chip. Additionally, there’s a fourth channel that game music emu calls “beeper” (and which Wikipedia describes as “one channel with 10 octaves”). Per my listening, it seems similar to the old PC speaker/honker. The metadata for a lot of the songs will specify either (AY) or (Beeper).

  Wrangling Metadata
  Large collections of AY files are easy to find ; as is typical for pure chiptunes, the files are incredibly small.

  As usual, the hardest part of the whole process was munging metadata. There seems to be 2 slightly different conventions for AY metadata, likely from 2 different people doing the bulk of the work and releasing the fruits of their labor into the wild. After I recognized the subtle differences between the 2 formats, it was straightforward to craft a tool to perform most of the work, leaving only a minimum of cleanup effort required afterwards.

  (As an aside, I think this process is called extract – transform – load, or ETL. Sounds fancy and complicated, yet it’s technically one of the first computer programming tasks I was ever paid to perform.)

  Collateral Damage
  While pushing this feature, I managed to break the site’s search engine. The search solution I developed was always sketchy (involving compiling a C program as a static binary CGI script and trusting it to run on the server). I will probably need to find a better approach, preferably sooner than later.

• FFProbe as .NET Process gives error while command line does not

  13 février 2024, par Ron O

  I've got a sample mp4 (a copy can be found here [sample_tagged.mp4, 562KB]) I've tagged with metadata using FFMpeg. Using a command line, if I issue a general command to view the metadata, I get everything.

  


  > ffprobe.exe -hide_banner -loglevel error -show_entries 'format_tags' sample_tagged.mp4
[FORMAT]
TAG:minor_version=512
TAG:major_brand=isom
TAG:compatible_brands=isomiso2avc1mp41
TAG:IMDB=tt0012345
TAG:Title=Sample MP4
TAG:synopsis=Watch MP4 sample
TAG:Rating=3.30
TAG:TMDB=tv/12345
TAG:Subtitle=Samples for all!
TAG:year=2000
TAG:date=2000:01:01T00:00:00
TAG:ReleaseDate=2000:01:01
TAG:genre=Beach;Windy;Sample
TAG:encoder=Lavf60.3.100
[/FORMAT]


  


  Also using the command line, if I limit it to a specific tag, I only get the specific tag as expected.

  


  > ffprobe.exe -hide_banner -loglevel error -show_entries 'format_tags=TMDB' sample_tagged.mp4
[FORMAT]
TAG:TMDB=tv/12345
[/FORMAT]


  


  I've set up a C# Process (in LINQPad) to mimic this behavior and return the results as a collection of key/value pairs.

  


  async Task Main()
{
  var sample = await FFProbe.GetProperties("sample_tagged.mp4");
  sample.Dump("Sample");

  var targeted = await FFProbe.GetProperties("sample_tagged.mp4", "TMDB");
  targeted.Dump("Sample Targeted");
}

class FFProbe
{
  const string _exeName = @"ffprobe.exe";
  const string _arguments = @"-hide_banner -loglevel error -show_entries 'format_tags{0}' ""{1}""";

  static Encoding _Utf8NoBOM = new UTF8Encoding(false);

  public static async Task>> GetProperties(string filename, params string[] targetProperties)
  {
    using (var probe = new Process())
    {
      var propsRead = new List>();

      probe.EnableRaisingEvents = true;
      probe.OutputDataReceived += (object sender, DataReceivedEventArgs e) =>
      {
        e.Dump("Output");
        if (e?.Data is null)
          return;
        
        if (e.Data.StartsWith("TAG"))
        {
          var eq = e.Data.IndexOf('=');

          if (eq > 1)
          {
            var key = e.Data.Substring(4, eq - 4);
            var value = e.Data.Substring(eq + 1).Trim();

            if (!targetProperties.Any() || targetProperties.Any(tp => key.Equals(tp, StringComparison.InvariantCultureIgnoreCase)))
            {
              if (value.Contains("\\r\\n"))
                value = value.Replace("\\r\\n", Environment.NewLine);

              propsRead.Add(new KeyValuePair(key, value));
            }
          }
        }
      };
      probe.ErrorDataReceived += (object sender, DataReceivedEventArgs e) =>
      {
        e.Dump("Error");
        if (e?.Data is null)
          return;
      };

      probe.StartInfo.FileName = _exeName;
      
      var tagLimiter = string.Empty;
      
      if (targetProperties.Any())
        tagLimiter = $"={string.Join(',', targetProperties)}";
      
      var arguments = string.Format(_arguments, tagLimiter, filename);
      arguments.Dump();

      probe.StartInfo.Arguments = arguments;
      probe.StartInfo.UseShellExecute = false;
      probe.StartInfo.CreateNoWindow = true;
      probe.StartInfo.RedirectStandardOutput = true;
      probe.StartInfo.RedirectStandardError = true;
      probe.StartInfo.StandardOutputEncoding = _Utf8NoBOM;
      probe.StartInfo.StandardErrorEncoding = _Utf8NoBOM;

      probe.Start();
      probe.BeginOutputReadLine();
      probe.BeginErrorReadLine();
      
      await probe.WaitForExitAsync();

      return propsRead;
    }
  }
}


  


  The output for the full sample dump matches the full metadata list. But when getting the targeted tag, I get two error responses.

  


  No match for section 'format_tags=TMDB'
Failed to set value ''format_tags=TMDB'' for option 'show_entries': Invalid argument


  


  From the output, the arguments sent into the process match those of the command line above :

  


  -hide_banner -loglevel error -show_entries 'format_tags=TMDB' "sample_tagged.mp4"


  


  I've copy/pasted the generated arguments to the command line call and it returns the value expected.

  


  What am I missing and/or need correction in setting up the call to get the same results via a Process as the command line ?

  


• Linux Media Player Survey Circa 2001

  2 septembre 2010, par Multimedia Mike — General

  Here’s a document I scavenged from my archives. It was dated September 1, 2001 and I now publish it 9 years later. It serves as sort of a time capsule for the state of media player programs at the time. Looking back on this list, I can’t understand why I couldn’t find MPlayer while I was conducting this survey, especially since MPlayer is the project I eventually started to work for a few months after writing this piece.

  For a little context, I had been studying multimedia concepts and tech for a year and was itching to get my hands dirty with practical multimedia coding. But I wanted to tackle what I perceived as unsolved problems– like playback of proprietary codecs. I didn’t want to have to build a new media playback framework just to start working on my problems. So I surveyed the players available to see which ones I could plug into and use as a testbed for implementing new decoders.

  Regarding Real Player, I wrote : “We’re trying to move away from the proprietary, closed-source “solutions”. Heh. Was I really an insufferable open source idealist back in the day ?

  Anyway, here’s the text with some Where are they now ? commentary [in brackets] :

  ---

  Towards an All-Inclusive Media Playing Solution for Linux

  I don’t feel that the media playing solutions for Linux set their sights high enough, even though they do tend to be quite ambitious.

  I want to create a media player for Linux that can open a file, figure out what type of file it is (AVI, MOV, etc.), determine the compression algorithms used to encode the audio and video chunks inside (MPEG, Cinepak, Sorenson, etc.) and replay the file using the best audio, video, and CPU facilities available on the computer.

  Video and audio playback is a solved problem on Linux ; I don’t wish to solve that problem again. The problem that isn’t solved is reliance on proprietary multimedia solutions through some kind of WINE-like layer in order to decode compressed multimedia files.

  Survey of Linux solutions for decoding proprietary multimedia
  updated 2001-09-01

  AVI Player for XMMS
  This is based on Avifile. All the same advantages and limitations apply.
  [Top Google hit is a Freshmeat page that doesn’t indicate activity since 2001-2002.]

  Avifile
  This player does a great job at taking apart AVI and ASF files and then feeding the compressed chunks of multimedia data through to the binary Win32 decoders.

  The program is written in C++ and I’m not very good at interpreting that kind of code. But I’m learning all over again. Examining the object hierarchy, it appears that the designers had the foresight to include native support for decoders that are compiled into the program from source code. However, closer examination reveals that there is support for ONE source decoder and that’s the “decoder” for uncompressed data. Still, I tried to manipulate this routine to accept and decode data from other codecs but no dice. It’s really confounding. The program always crashes when I feed non-uncompressed data through the source decoder.
  [Lives at http://avifile.sourceforge.net/ ; not updated since 2006.]

  Real Player
  There’s not much to do with this since it is closed source and proprietary. Even though there is a plugin architecture, that’s not satisfactory. We’re trying to move away from the proprietary, closed-source “solutions”.
  [Still kickin’ with version 11.]

  XAnim
  This is a well-established Unix media player. To his credit, the author does as well as he can with the resources he has. In other words, he supports the non-proprietary video codecs well, and even has support for some proprietary video codecs through binary-only decoders.

  The source code is extremely difficult to work with as the author chose to use the X coding format which I’ve never seen used anywhere else except for X header files. The infrastructure for extending the program and supporting other codecs and file formats is there, I suppose, but I would have to wrap my head around the coding style. Maybe I can learn to work past that. The other thing that bothers me about this program is the decoding approach : It seems that each video decoder includes routines to decompress the multimedia data into every conceivable RGB and YUV output format. This seems backwards to me ; it seems better to have one decoder function that decodes the data into its native format it was compressed from (e.g., YV12 for MPEG data) and then pass that data to another layer of the program that’s in charge of presenting the data and possibly converting it if necessary. This layer would encompass highly-optimized software conversion routines including special CPU-specific instructions (e.g., MMX and SSE) and eliminate the need to place those routines in lots of other routines. But I’m getting ahead of myself.
  [This one was pretty much dead before I made this survey, the most recent update being in 1999. Still, we owe it much respect as the granddaddy of Unix multimedia playback programs.]

  Xine
  This seems like a promising program. It was originally designed to play MPEGs from DVDs. It can also play MPEG files on a hard drive and utilizes the Xv extensions for hardware YUV playback. It’s also supposed to play AVI files using the same technique as Avifile but I have never, ever gotten it to work. If an AVI file has both video and sound, the binary video decoder can’t decode any frames. If the AVI file has video and no sound, the program gets confused and crashes, as far as I can tell.

  Still, it’s promising, and I’ve been trying to work around these crashes. It doesn’t yet have the type of modularization I’d like to see. Right now, it tailored to suit MPEG playback and AVI playback is an afterthought. Still, it appears to have a generalized interface for dropping in new file demultiplexers.

  I tried to extend the program for supporting source decoders by rewriting w32codec.c from scratch. I’m not having a smooth time of it so far. I’m able to perform some manipulations on the output window. However, I can’t get the program to deal with an RGB image format. It has trouble allocating an RGB surface with XvShmCreateImage(). This isn’t suprising, per my limited knowledge of X which is that Xv applies to YUV images, but it could also apply to RGB images as well. Anyway, the program should be able to fall back on regular RGB pixmaps if that Xv call fails.

  Right now, this program is looking the most promising. It will take some work to extend the underlying infrastructure, but it seems doable since I know C quite well and can understand the flow of this program, as opposed to Avifile and its C++. The C code also compiles about 10 times faster.
  [My home project for many years after a brief flirtation with MPlayer. It is still alive ; its latest release was just a month ago.]

  XMovie
  This library is a Quicktime movie player. I haven’t looked at it too extensively yet, but I do remember looking at it at one point and reading the documentation that said it doesn’t support key frames. Still, I should examine it again since they released a new version recently.
  [Heroine Virtual still puts out some software but XMovie has not been updated since 2005.]

  XMPS
  This program compiles for me, but doesn’t do much else. It can play an MP3 file. I have been able to get MPEG movies to play through it, but it refuses to show the full video frame, constricting it to a small window (obviously a bug).
  [This project is hosted on SourceForge and is listed with a registration date of 2003, well after this survey was made. So the project obviously lived elsewhere in 2001. Meanwhile, it doesn’t look like any files ever made it to SF for hosting.]

  XTheater
  I can’t even get this program to compile. It’s supposed to be an MPEG player based on SMPEG. As such, it probably doesn’t hold much promise for being easily extended into a general media player.
  [Last updated in 2002.]

  GMerlin
  I can’t get this to compile yet. I have a bug report in to the dev group.
  [Updated consistently in the last 9 years. Last update was in February of this year. I can’t find any record of my bug report, though.]