Error in JS?

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  • Grzegorz
    #1

    Error in JS?

    Hi All,

    I encountered recently the following strange behavior of JS:
    I need to create a simple page that contains one button. After clicking it
    there should be generated two short sounds with a 0,5s gap between them. The
    code looks as follows:

    <html>
    <EMBED SRC="sound1.wav " LOOP=FALSE AUTOSTART=false HIDDEN=true>
    <EMBED SRC="sound2.wav " LOOP=FALSE AUTOSTART=false HIDDEN=true>

    <script language="JavaS cript">

    function PlaySounds() {
    document.embeds[0].play();
    for (j=1;j<=100000; j++) {a=Math.log(1)}
    document.embeds[1].play();
    }

    </script>
    <button onClick="PlaySo unds()">Play sounds</button>
    </html>

    Please look at three rows of PlaySounds function. The for loop is used to
    introduce 0,5 s delay, but depending on processor speed it may take longer
    or shorter.
    It seems like there should be emitted the first sound, then 0,5 silence and
    second sound. As I experienced IT IS NOT SO! First there is the loop
    executed and then both sounds mixed, emitted simultaneously!
    Why???
    And the second qestion, how to achieve desired effect? Please do not advice
    me the setTimeout function because with long series of sound samples it
    works improperly.

    Regards,
    Grzegorz


    Tags: None
    • Martin Honnen
      #2
      Re: Error in JS?



      Grzegorz wrote:
      [color=blue]
      > I encountered recently the following strange behavior of JS:
      > I need to create a simple page that contains one button. After clicking it
      > there should be generated two short sounds with a 0,5s gap between them. The
      > code looks as follows:
      >
      > <html>
      > <EMBED SRC="sound1.wav " LOOP=FALSE AUTOSTART=false HIDDEN=true>
      > <EMBED SRC="sound2.wav " LOOP=FALSE AUTOSTART=false HIDDEN=true>
      >
      > <script language="JavaS cript">
      >
      > function PlaySounds() {
      > document.embeds[0].play();
      > for (j=1;j<=100000; j++) {a=Math.log(1)}
      > document.embeds[1].play();
      > }
      >
      > </script>
      > <button onClick="PlaySo unds()">Play sounds</button>
      > </html>
      >
      > Please look at three rows of PlaySounds function. The for loop is used to
      > introduce 0,5 s delay, but depending on processor speed it may take longer
      > or shorter.
      > It seems like there should be emitted the first sound, then 0,5 silence and
      > second sound. As I experienced IT IS NOT SO! First there is the loop
      > executed and then both sounds mixed, emitted simultaneously!
      > Why???
      > And the second qestion, how to achieve desired effect? Please do not advice
      > me the setTimeout function because with long series of sound samples it
      > works improperly.[/color]

      Use setTimeout. Your loop blocks the browser.

      --

      Martin Honnen
      Attention Required! | Cloudflare
      http://JavaScript.FAQTs.com/


        Comment

        • HikksNotAtHome
          #3
          Re: Error in JS?

          In article <bs97mf$6id$1@n ews.onet.pl>, "Grzegorz" <grzeslaw@op.pl > writes:
          [color=blue]
          >Hi All,
          >
          >I encountered recently the following strange behavior of JS:
          >I need to create a simple page that contains one button. After clicking it
          >there should be generated two short sounds with a 0,5s gap between them. The
          >code looks as follows:[/color]
          [color=blue]
          ><script language="JavaS cript">[/color]

          use type="text/javascript" instead, language is deprecated.
          [color=blue]
          >function PlaySounds() {
          >document.embed s[0].play();
          >for (j=1;j<=100000; j++) {a=Math.log(1)}
          >document.embed s[1].play();
          >}
          >
          ></script>
          ><button onClick="PlaySo unds()">Play sounds</button>
          >
          >Please look at three rows of PlaySounds function. The for loop is used to
          >introduce 0,5 s delay, but depending on processor speed it may take longer
          >or shorter.[/color]

          No, you think its introducing a 1/2 second delay, but as you say, it doesn't
          work. Thats not how you do it in javascript.
          [color=blue]
          >It seems like there should be emitted the first sound, then 0,5 silence and
          >second sound. As I experienced IT IS NOT SO! First there is the loop
          >executed and then both sounds mixed, emitted simultaneously!
          >Why???[/color]

          Because too many other things can affect the speed at which it happens. My IE6
          executes it the same way. But my processor is fast. On a 386 processor, it
          would run slower.
          [color=blue]
          >And the second qestion, how to achieve desired effect? Please do not advice
          >me the setTimeout function because with long series of sound samples it
          >works improperly.[/color]

          If you do not want to use the proper way to introduce a delay, your only other
          option would be to edit the sound files and make a new file, with the delays
          built in.

          Or, use a blank sound file (of 1/2 second length) and then instead of embedding
          the sounds, embed an .m3u file instead and play it.
          --
          Randy

            Comment

            • Brian Genisio
              #4
              Re: Error in JS?

              Grzegorz wrote:
              [color=blue]
              > Hi All,
              >
              > I encountered recently the following strange behavior of JS:
              > I need to create a simple page that contains one button. After clicking it
              > there should be generated two short sounds with a 0,5s gap between them. The
              > code looks as follows:
              >
              > <html>
              > <EMBED SRC="sound1.wav " LOOP=FALSE AUTOSTART=false HIDDEN=true>
              > <EMBED SRC="sound2.wav " LOOP=FALSE AUTOSTART=false HIDDEN=true>
              >
              > <script language="JavaS cript">
              >
              > function PlaySounds() {
              > document.embeds[0].play();
              > for (j=1;j<=100000; j++) {a=Math.log(1)}
              > document.embeds[1].play();
              > }
              >
              > </script>
              > <button onClick="PlaySo unds()">Play sounds</button>
              > </html>
              >
              > Please look at three rows of PlaySounds function. The for loop is used to
              > introduce 0,5 s delay, but depending on processor speed it may take longer
              > or shorter.
              > It seems like there should be emitted the first sound, then 0,5 silence and
              > second sound. As I experienced IT IS NOT SO! First there is the loop
              > executed and then both sounds mixed, emitted simultaneously!
              > Why???
              > And the second qestion, how to achieve desired effect? Please do not advice
              > me the setTimeout function because with long series of sound samples it
              > works improperly.
              >
              > Regards,
              > Grzegorz
              >
              >[/color]

              You are hearing them at the same time, likely, because the sound does
              not actually play, until the javascript block has ended. The message to
              play the sound is queued up, and when the block ends, it plays it... and
              the next one.

              There have only been, in my experience, a few situations where
              busy-waits are appropriate when programming... and they have all been in
              embedded systems, at the microprocessor level. In _ALL_ other cases,
              the programming environment provided me with the resources to do a
              non-blocking sleep.

              In Javascript, it is setTimeout. I am not familiar with embedding
              sounds, but you _might_ be able to use setTimeout to probe when the
              sound has finished, and set the next timeout to play the next sound...
              just a stab in the dark.

              Brian

                Comment

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