BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  waveOut CALLBACK question          BorlandTalk.com Forum Index -> Delphi Multimedia View previous topic :: View next topic   Author Message jh Guest Posted: Sat Oct 22, 2005 10:36 pm    Post subject: waveOut CALLBACK question Hi, I'm using Delphi 2005 Pro. I have found very few examples of using low level API for wave in/out. I can play or record audio data but still have some problems with reseting devices or playing with different cards sometimes hangs my application. 1. waveOutOpen uses callback with CALLBACK_WINDOW/FUNCTION/THREAD/EVENT. What are advantages of using these callbacks? I mean when e.g. CALLBACK_FUNCTION could be a better way than using CALLBACK_WINDOW? Callback window needs handle. OK, even when I'm creating my own class based on TObject I can get handle. And in most cases it works. CALLBACK_FUNCTION. With my onboard card it "almost" works, with my pro RME audio card it doesn't. Almost, because waveOutReset hangs the application, while waveOutPrepareHeader and waveOutWrite doesn't. MS SDK that it's not allowed using any waveOut function from callback function. OK. It looks that I can only post a message within waveOutProc. So finally it looks like CALLBACK_WINDOW... So where's the difference? 2. CALLBACK_EVENT and CALLBACK_THREAD. I haven't found any example... How should I use it? BTW. How can I play 24 bit wave files? I mean 24-bit stream, no 24 bit reduced to 16 bit like many players do.... thanks, Jacek Back to top Jens Gruschel Guest Posted: Sun Oct 23, 2005 12:04 pm    Post subject: Re: waveOut CALLBACK question Quote: I'm using Delphi 2005 Pro. I have found very few examples of using low level API for wave in/out. I can play or record audio data but still have some problems with reseting devices or playing with different cards sometimes hangs my application. I'm using waveOut... and a callback window without any problems. Could you provide some code? (I've posted some code of mine to the attachment newsgroup). Quote: BTW. How can I play 24 bit wave files? I mean 24-bit stream, no 24 bit reduced to 16 bit like many players do.... Haven't tried it, but should be possible, if you sound card does support it. You can use waveOutOpen with WAVE_FORMAT_QUERY to see whether some format is supported by a device (and it should be possible to enumerate all formats, although I don't remember how exactly this is done). Jens -- Jens Gruschel http://www.pegtop.net Back to top alanglloyd@aol.com Guest Posted: Mon Oct 24, 2005 9:13 am    Post subject: Re: waveOut CALLBACK question Quote: Almost, because waveOutReset hangs the application, while waveOutPrepareHeader and waveOutWrite doesn't. I know there is a stated limitaion to what you may call in a callback function in waveOut. But there is also another gotcha. waveOutReset stops the wave recording, _but_ returns all the buffers immediately with a done flag. Therefore your code handling the buffers must still be active until all the buffers have been returned. I found that in order to stop AVs I had to count the buffers in the queue and only call waveOutClose after the queue was empty. waveInStop has similar gotchas. I have an example in Delphi of using CALLBACK_EVENT. If that is any use to you, email me and I will send it. Alan Lloyd Back to top Thaddy Guest Posted: Mon Oct 24, 2005 4:21 pm    Post subject: Re: waveOut CALLBACK question Quote: BTW. How can I play 24 bit wave files? I mean 24-bit stream, no 24 bit reduced to 16 bit like many players do.... Try waveioX.pas available as freeware from http://www.tobybear.de This file is an extension of Carlos Barbosa's WaveIo, but supports all known wave formats including 24, 32 and 64 bit integer and 32 bit floating point. 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