Adjust Audio Play Rate

[bidgeeman]

Hi.
Can someone tell me if it is possible to adjust the playspeed of a player
so that the speed will slow and then speed up? Sort of like the playspeed is on a curve?

Many thanks
Bidge

[Klaus]

Hi Bidge,

check "playtrate" (= speed) in the docs!
Setting the playrate of a player to 1 = "normal" speed
2 = double speed
You can use fractions like 1.3 etc...

Using negative values = playing the sound backwards

Hint!
Keep in mind that this does also change the pitch of your sounds!
Although QuickTime is capable to keep the pitch while changing the playrate,
RunRev did not (yet?) implement this QT API call in the player obhjects!


Best

Klaus

[dickey]

G'day Bidge,

I believe this can be achieved in AppleScript. Please refer this link on macosxhints dot com http://www.macosxhints.com/article.php? ... 3000452805, in reference to changing the playback speed of the player without changing pitch.

I hope this helps my fellow Australian.

Kind regards, Andrew

[Klaus]

I'm sure Bidge wants to use this inside of Rev

[bidgeeman]

Hey. Thanks for all the responses

Could it be possible to adjust the playrate so that they are different as the audio plays? Say that at the start of an audio file the playrate is 1.6, the middle, .7, and the end 1.9 ?

Cheers
Bidge

[bn]

Bidge,

... Say that at the start of an audio file the playrate is 1.6, the middle, .7, and the end 1.9 ?

try this in the script of a player you want to play at different playrates during playing:

Code: Select all

local tIsPlaying, tDuration, tPlayRateAtBegin, tPlayRateMiddle, tPlayRateEnd

on playstarted
   put true into tIsPlaying
   put the duration of me into tDuration
   put 1.6 into tPlayRateAtBegin -- adjust for start rate
   put 0.7 into tPlayRateMiddle -- adjust for middle rate
   put 1.9 into tPlayRateEnd -- adjust for end rate
   send adJustPlayrate to me in 1 milliseconds
end playstarted

on adJustPlayrate
   if not tIsPlaying then  exit adJustPlayrate
   put the currenttime of me into tCurrent
   put  trunc (tCurrent / tDuration * 100) into tPercent
   if tPercent < 50 then
      put tplayRateMiddle+((tPlayRateAtBegin-tplayRateMiddle)* (1-(tPercent*2/100))) into tplayRateNow
      set the playrate of me to tplayRateNow
   else
      put tplayRateMiddle+((tPlayRateEnd-tplayRateMiddle)* ((tPercent/100 -.5)*2)) into tplayRateNow
      set the playrate of me to tplayRateNow
   end if
   if adJustPlayrate is not in the pendingmessages then
      send adjustPlayrate to me in 10 milliseconds
   end if
end adJustPlayrate

on playstopped
   put false into tIsPlaying
   repeat for each line aline in the pendingmessages
      if aline contains "adJustPlayrate" then cancel item 1 of aLine
   end repeat
end playstopped

on mouseDown
   if  tIsplaying then put false into tIsPlaying
end mouseDown

regards
Bernd

[SparkOut]

Oh that's great Bernd! Love the effect of the sliding change in speed.

I know that's exactly what you wanted to achieve Bidge, but just to add another angle, you can also use callbacks at certain points - so this is an alternative where the playRate stays constant until it reaches the callback trigger time. So the first third will play at the constant rate of 1.6, the middle third at 0.7 and the final third at 1.9 - jumping from one rate to another, rather than sliding. I offer this only as an illustration of the use of callbacks, which I know is not appropriate for tackling this particular task. Sorry!
In your initialisation:

Code: Select all

   put the duration of player "Player" into tDuration
   put tDuration / 3 into tInt
   put "0,adjustRate 1.0" into tCallbacks
   --just to reset for tidiness 
   put cr & "1,adjustRate 1.6" after tCallbacks
   put cr & round (tInt) & ",adjustRate 0.7" after tCallbacks
   put cr & round ((2 * tInt)) & ",adjustRate 1.9" after tCallbacks
   put cr & (tDuration - 1) & ",adjustRate 1.0" after tCallbacks
   --just to reset for tidiness
   set the callbacks of player "Player" to tCallbacks
   start player "Player"

In the player:

Code: Select all

on adjustRate pRate
   set the playRate of me to pRate
end adjustRate

[bn]

great Sparkout,
I didn't even think of callbacks since I like "send in time" too much
If one wants to go with callbacks, (which at times are very handy) one could do the sliding pitch / rate like this in a separate button

Code: Select all

on mouseUp
   put the duration of player 2 into tDuration
   put 1.6 into tPlayRateAtBegin -- adjust for start rate
   put 0.7 into tPlayRateMiddle -- adjust for middle rate
   put 1.9 into tPlayRateEnd -- adjust for end rate
   put trunc (tDuration / 100) into tIntervall
   put 0 into tSetCallbackAt
   put "" into tmyCallbacks
   repeat with i = 1 to 100
      if i < 50 then
         put tplayRateMiddle+((tPlayRateAtBegin-tplayRateMiddle)* (1-(i*2/100))) into tplayRateNow
         put tSetCallbackAt & ",adjustRate" && tPlayRateNow & return after tmyCallbacks
      else
         put tplayRateMiddle+((tPlayRateEnd-tplayRateMiddle)* ((i/100 -.5)*2)) into tplayRateNow
         put tSetCallbackAt & ",adjustRate" && tPlayRateNow & return after tmyCallbacks
      end if
      add tIntervall to tSetCallbackAt
   end repeat
   delete char - 1 of tmyCallbacks
   set the callbacks of player 2 to tmyCallbacks
end mouseUp

in the player would be the code you provided

Code: Select all

on adjustRate pRate
   set the playRate of me to pRate
end adjustRate

Now if someone could offer a better algorithm to replace my cheesy calculation of the playrate, I wonder if there are any mathematicians around
regards
Bernd

[bidgeeman]

WOW! That's fantastic! Thanks guys but there is one major problem I have now realized
When I tried to save out the .wav file using QT External the playrate data is not saved with
the .wav. Dammit!

Cheers
Bidge

[bn]

Bidge,
I dont see a way in the quicktime external or with Revs sound recording capabilities to create a sound file with the change of pitch/rate preserved. (I did record a sound file via the internal microphone on a MacBook Pro with pictch changes with Rev's " record sound file theFile" but that is quite lossy/low quality and probably not what you want)
regards
Bernd

[bidgeeman]

Hi Bernd.
Thanks for trying. It's a pity that you can't save the soundfile preserved. The lack of audio control really limits Rev fom being a useful tool for creating sound applications.

Cheers mate
David