Bug 977 – QAudioOutput won't play short files

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Bug 977 - QAudioOutput won't play short files

Summary:

QAudioOutput won't play short files

Status:	CLOSED WONTFIX

Product:	PySide
Classification:	Unclassified
Component:	PySide
Version:	1.0.6
Platform:	All All

Importance:	P3 normal
Assigned To:	renato filho

URL:

Depends on:
Blocks:
	Show dependency tree / graph

Reported:	2011-08-17 23:32 EEST by Daniel Ashbrook
Modified:	2011-09-21 21:19 EEST (History)
CC List:	8 users (show)

See Also:

Attachments
Simple example to illustrate need for padding of short sounds (1.25 KB, text/x-python-script) 2011-08-17 23:32 EEST, Daniel Ashbrook	Details
c++ port of the example (11.11 KB, application/x-bzip) 2011-08-31 20:04 EEST, renato filho	Details
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Description Daniel Ashbrook 2011-08-17 23:32:39 EEST

Created attachment 406 [details]
Simple example to illustrate need for padding of short sounds

Audio data must be padded to the QAudioOutput.periodSize() in order to play;
otherwise, QAudioOutput does not play.

See the attachment for sample code: with a short (256 byte) sound and 'pad' set
to False, you'll hear nothing; with 'pad' set to True, you'll hear a pop.

Comment 1 Hugo Parente Lima 2011-08-23 20:30:25 EEST

Here I got an assertion error inside the Qt plugin, maybe because I don't use
Pulse Audio, i.e. a Qt bug.

"Connection failure: Connection refused"                                        
Assertion 'c' failed at pulse/context.c:1182, function
pa_context_send_simple_command(). Aborting.                                     
Aborted

Comment 2 renato filho 2011-08-31 17:35:40 EEST

Sorry but I do not understand the problem, I'm running the test without
modifications and I got:

padding 256 bytes to 3528 bytes
active
error: PySide.QtMultimedia.QAudio.Error.NoError
idle
error: PySide.QtMultimedia.QAudio.Error.UnderrunError

If I change the pad value from True to False I got:

active
error: PySide.QtMultimedia.QAudio.Error.NoError
idle
error: PySide.QtMultimedia.QAudio.Error.UnderrunError

And If I uncomment the line "w = WaveAudioOutput(2**18)" and commented the line
"w = WaveAudioOutput(256, pad=False)"

I heard the noise and I got:

padding 262144 bytes to 3528 bytes
active
error: PySide.QtMultimedia.QAudio.Error.NoError
idle
error: PySide.QtMultimedia.QAudio.Error.UnderrunError



What is exactly the problem? How can I reproduce that?

Comment 3 Daniel Ashbrook 2011-08-31 19:55:40 EEST

With:
  w = WaveAudioOutput(256, pad=True)
you should hear a short "pop" sound from your speakers.

With:
  w = WaveAudioOutput(256, pad=False)
you should not hear the "pop" sound. This is the bug.

With both:
  w = WaveAudioOutput(2**18, pad=True)
  w = WaveAudioOutput(2**18, pad=False)
you should hear sound.

The issue is that the sound must be a certain length to hear; with pad=True, I
am padding the buffer to 3528 bytes - so adding 3528-256=3272 zeros to the end.
The padding causes the sound to play. Without that padding, you don't get sound
output, but should!

Comment 4 renato filho 2011-08-31 20:03:09 EEST

Running the same test with C++ example:

1 - With: WaveAudioOutput *out = new WaveAudioOutput(255, true);
padding 255 bytes to 3528 bytes 
STATE: "active" 
ERROR: "NoError" 
STATE: "idle" 
ERROR: "UnderrunError"

2 - With: 
STATE: "active" 
ERROR: "NoError"
and the program freeze

3 - WaveAudioOutput *out = new WaveAudioOutput(pow(2,18));
I heard the noise and:
padding 262144 bytes to 3528 bytes 
STATE: "active" 
ERROR: "NoError" 
STATE: "idle" 
ERROR: "UnderrunError"

Comment 5 renato filho 2011-08-31 20:04:19 EEST

Created attachment 414 [details]
c++ port of the example

Comment 6 renato filho 2011-08-31 20:08:15 EEST

I have created this c++ that produces the same results as python code.

could you confirm that?

If the C++ shows the same problem then this is a bug on Qt multimedia and must
be reported on Qt bug tracker
(https://bugreports.qt.nokia.com/secure/Dashboard.jspa).

Comment 7 renato filho 2011-09-08 23:59:09 EEST

I will mark this bug as closed since the problem exists in both C++ and Python,
but fell free to re-open if you have any other problem.

Comment 8 renato filho 2011-09-21 21:19:48 EEST

Release 1.0.7