Regarding inability of Python Module Winsound to produce beep in decimal frequency

[Steve]

"The HAL (hardware abstraction layer) function HalMakeBeep()"
Is the beep that opens the pod bay doors?


Footnote:
 George Melly remarked to Mike Jagger on how lined his face was for one so
young. Jagger replied “They’re laughter lines George” to which Melly
countered: “Mick, nothing’s that f**king funny!”.

-----Original Message-----
From: Python-list <python-list-bounces+gronicus=sga.ninja at python.org> On
Behalf Of Eryk Sun
Sent: Tuesday, August 17, 2021 6:23 PM
To: Dennis Lee Bieber <wlfraed at ix.netcom.com>
Cc: python-list at python.org
Subject: Re: Regarding inability of Python Module Winsound to produce beep
in decimal frequency

On 8/17/21, Dennis Lee Bieber <wlfraed at ix.netcom.com> wrote:
> On Tue, 17 Aug 2021 15:11:05 +1000, Chris Angelico <rosuav at gmail.com> 
> declaimed the following:
>
>>Huh. Okay. Then I withdraw the concern from this list, and instead lay 
>>it at Microsoft's feet. That is, I maintain, a bizarre choice. Surely 
>>there are better ways to trigger audio on the sound card?
>
> 	Possibly there is a section of code that determines if a sound card 
> is available, and if not, routes to the basic internal speaker. The 
> rest of the wave form logic is probably still of use for that.

It may be that there's a fallback audio device that uses the PC speaker on
systems that lack even basic audio support in their chipset. But in common
practice, Beep() does not use the PC speaker.

The "beep.sys" driver in Windows 7+ has no code path that starts a PC
speaker beep via HalMakeBeep(frequency) and ends it after a timeout via
HalMakeBeep(0), which was the old implementation of "beep.sys"
that can still be seen in ReactOS [1].

The HAL (hardware abstraction layer) function HalMakeBeep() is still
implemented in Windows 10, but without the connection to an IOCTL in
"\Device\Beep", or some other installed device driver, there's no way for
user-mode code to make a beep with the classic PC speaker.

In Windows 7+, the beep device's IOCTL_BEEP_SET function is just a relay.
It's implemented by searching for and completing a queued IOCTL request from
a task in the user's session (i.e. an inverted callback from kernel mode to
user mode). This task, which is scheduled to run at logon in every
interactive session, executes the "PlaySoundSrv.dll"
module in an instance of "taskhostw.exe". Upon completion of its queued
IOCTL, from which it gets the beep frequency and duration, the sound server
generates the requested beep waveform and plays it on the default audio
output device via WinAPI PlaySound().

Notably, the "beep.sys" driver doesn't support manually starting the
sound-server task in the user's session. So if one terminates the
"taskhostw.exe" process that's hosting "PlaySoundSrv.dll", WinAPI
Beep() will no longer work. To get it back, the
"\Microsoft\Windows\Multimedia\SystemSoundsService" task has to be restarted
manually.

---

[1]
https://github.com/reactos/reactos/blob/master/drivers/base/beep/beep.c#L295
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