Question

I would like to build a program which lets lyrics of a song run over the screen. Something like this:

http://www.youtube.com/watch?v=kIAiBvD9njM

Can you help me?

Algorithm:

• pushes the marker to the right of a line fitting the music
• lets a line above the current line disappear
• inserts a new line above the current line

What is needed?

• lyrics of the song (line per line)
• time to text data? (when does a line start/end)

Some approaches would help me a lot. Pseudo-code or even Delphi code of any part would be fantastic.

Answer 1

let’s assume you have a text file with the text to be shown and the annotated time of when to hightlight it (kind of a subtitles file, for example the standard proposal w3c timed text (http://www.w3.org/AudioVideo/TT/) or the SUB – Movie subtitle file format in use by several media players.

Your program must first read and parse the text file, and decode the annotated time. Insert it in a stringlist called Subtitles which items would also keep objects similar to this one

type tSubtitle = class
  num : integer;
  prevTime, fromTime : tdatetime;
  toTime, nextTime: tdatetime;
  text: string;
end;

You might want to extend the object to hold some highlighting attributes as well.

Then you just need to display those objects synchronized with a timer.

procedure TForm1.Timer1Timer(Sender: TObject);
var rt : TDateTime;
    done:boolean; 
    si,st,sb:integer; 
    s:string;
begin
  rt:=now-startTime;
  st:=0;
  sb:=subtitles.Count;  // binary search the subtitle for the current time
  repeat
     si:=(st+sb) div 2;
     s:=TSubtitle(subtitles.Objects[si-1]);
     done:= ((t>=s.prevTime) and (t<=s.nextTime));
     if not done then 
     begin
        if t>s.prevTime then st:=si 
        else if t<s.nextTime then sb:=si;
        if st=sb then done:=true;
     end;
  until done;
  // do what you want with s
end;