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Bug
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Resolution: Fixed
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P2: Important
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6.3.2, 6.5.2, 6.6.0 Beta2
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None
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Windows
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9fcfa21aa (dev), 34e6dec02 (6.6), d2feae42c (dev), 77050605b (6.6), ff4ddd4d5 (6.5), 0caa9caea (6.5)
Audio recording does not start immediately. There is a delay (about a second) between calling the record() function and starting to actually record the sound.
Sample code:
import QtQuick import QtQuick.Window import QtMultimedia Window { width: 640 height: 480 visible: true CaptureSession { id: captureSession audioInput: AudioInput {} recorder: MediaRecorder { id: recorder onRecorderStateChanged: function (state) { if (state === MediaRecorder.RecordingState) { console.log('Recording started') console.timeEnd('Initialization cost') } } onErrorOccurred: function (error, errorString) { console.log('Error: ' + error + ' (' + errorString + ')') } } } Component.onCompleted: { console.time('Initialization cost') console.log('Start recording...') recorder.record() } }
Just run it and check console output.
qml: Start recording... qml: Recording started Initialization cost: 1720ms
The problem analysis:
When recording starts, the QMediaFormat::resolveForEncoding() function is called internally, which enumerates all system codecs and supported file formats, also for video, regardless of whether video recording is actually required. This happens directly in QWindowsFormatInfo constructor.
On my system (Win 10 with standard system codecs) enumerating video codecs takes about 900-12000ms (in a release build). Note that this not only delays the recording, but also blocks the UI thread for a while.
Just a sample call stack when pausing execution during recorder initialization:
1 NtMapViewOfSection ntdll 0x7ffd4bc4d514
2 umppc17010 0x1b1b0ef7963
3 umppc17010 0x1b1b0ef7d09
4 RtlIsCriticalSectionLockedByThread ntdll 0x7ffd4bbc4d42
5 RtlIsCriticalSectionLockedByThread ntdll 0x7ffd4bbc4aaa
6 RtlUnlockHeap ntdll 0x7ffd4bc0fd93
7 RtlUnlockHeap ntdll 0x7ffd4bc0fac0
8 RtlUnlockHeap ntdll 0x7ffd4bc0ed5f
9 RtlGetFullPathName_UstrEx ntdll 0x7ffd4bbcfb53
10 RtlDosPathNameToNtPathName_U ntdll 0x7ffd4bbc73e4
11 LdrLoadDll ntdll 0x7ffd4bbc6af4
12 LoadLibraryExW KERNELBASE 0x7ffd496556b2
13 LoadLibraryExA KERNELBASE 0x7ffd4964e6a1
14 OpenAdapter10_2 igd10um64gen11 0x7ffd3193417b
15 GTPin_Init igd10um64gen11 0x7ffd31ad80d6
16 OpenAdapter10_2 igd10um64gen11 0x7ffd319a1673
17 D3DKMTWaitForVerticalBlankEvent d3d11 0x7ffd44d8617e
18 EnableFeatureLevelUpgrade d3d11 0x7ffd44d07f8e
19 D3D11CoreCreateDevice d3d11 0x7ffd44d3cc26
20 D3D11CoreCreateDevice d3d11 0x7ffd44d3c676
21 D3D11CoreCreateDevice d3d11 0x7ffd44d2df03
22 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b67958
23 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b677f4
24 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b662e2
25 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b66a73
26 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b6655e
27 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b98d8a
28 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b8ccbc
29 DllUnregisterServer mfx_mft_mjpgvd_64 0x7ffcb7b8eccf
30 CoGetTreatAsClass combase 0x7ffd49de5134
31 StringFromGUID2 combase 0x7ffd49d91a00
32 CoGetTreatAsClass combase 0x7ffd49de58bc
33 CoDisableCallCancellation combase 0x7ffd49e21b88
34 Ordinal167 combase 0x7ffd49e26a90
35 CoTaskMemRealloc combase 0x7ffd49e1eff1
36 CoDisableCallCancellation combase 0x7ffd49e21dc0
37 StringFromGUID2 combase 0x7ffd49d91a00
38 StringFromGUID2 combase 0x7ffd49d8dc6f
39 StringFromGUID2 combase 0x7ffd49d91a00
40 CoCreateInstance combase 0x7ffd49d7bd2a
41 CoCreateInstance combase 0x7ffd49d7a7d0
42 CoCreateInstance combase 0x7ffd49d7a52c
43 MFGetAttributesAsBlob MFPlat 0x7ffd4321da68
44 MFGetAttributesAsBlob MFPlat 0x7ffd4321d764
45 MFInitVideoFormat_RGB MFPlat 0x7ffd4322e3fc
46 MFEnumLocalMFTRegistrations MFPlat 0x7ffd4322fb78
47 getCodecSet<enum QMediaFormat::VideoCodec> qwindowsformatinfo.cpp 49 0x7ffcedb91b59
48 QWindowsFormatInfo::QWindowsFormatInfo qwindowsformatinfo.cpp 153 0x7ffcedb90cbf
49 QWindowsMediaIntegration::formatInfo qwindowsintegration.cpp 55 0x7ffcedbac567
50 formatInfo qmediaformat.cpp 462 0x7ffcbc847231
51 QMediaFormat::supportedFileFormats qmediaformat.cpp 504 0x7ffcbc846021
52 QMediaFormat::resolveForEncoding qmediaformat.cpp 789 0x7ffcbc846cea
53 QMediaEncoderSettings::resolveFormat qplatformmediarecorder_p.h 52 0x7ffcbc80594a
54 QMediaRecorder::record qmediarecorder.cpp 347 0x7ffcbc874716
55 QMediaRecorder::qt_static_metacall moc_qmediarecorder.cpp 331 0x7ffcbc872955
56 QMediaRecorder::qt_metacall moc_qmediarecorder.cpp 525 0x7ffcbc8726ab
57 QMetaObject::metacall qmetaobject.cpp 335 0x7ffcae4bf939
58 QQmlObjectOrGadget::metacall qqmlobjectorgadget.cpp 15 0x7ffcb182c9e0
59 QV4::CallMethod qv4qobjectwrapper.cpp 1542 0x7ffcb147e1eb
60 QV4::CallPrecise qv4qobjectwrapper.cpp 1834 0x7ffcb147f51c
61 <lambda_3e8464433ed092c25780b342b967fe3f>::operator() qv4qobjectwrapper.cpp 2731 0x7ffcb1481b53
62 <lambda_4473c4284921ec2280ffebb7045bfe66>::operator()<<lambda_3e8464433ed092c25780b342b967fe3f>> qv4qobjectwrapper.cpp 2709 0x7ffcb148d1fc
63 QV4::QObjectMethod::callInternal qv4qobjectwrapper.cpp 2731 0x7ffcb14784ae
64 QV4::QObjectMethod::virtualCall qv4qobjectwrapper.cpp 2621 0x7ffcb1477ddc
65 QV4::FunctionObject::call qv4functionobject_p.h 172 0x7ffcb12afbed
66 QV4::Moth::VME::interpret qv4vme_moth.cpp 902 0x7ffcb155c501
67 QV4::Moth::VME::exec qv4vme_moth.cpp 584 0x7ffcb1558b35
68 QV4::doCall qv4function.cpp 54 0x7ffcb13d4647
69 QV4::Function::call qv4function.cpp 80 0x7ffcb13d3876
70 <lambda_f15eb9b3a6e26b3d0034fc979a0ed169>::operator() qv4function.cpp 31 0x7ffcb13d441d
71 QV4::convertAndCall<<lambda_f15eb9b3a6e26b3d0034fc979a0ed169>> qv4jscall_p.h 185 0x7ffcb13d7439
72 QV4::Function::call qv4function.cpp 27 0x7ffcb13d352e
73 QQmlJavaScriptExpression::evaluate qqmljavascriptexpression.cpp 270 0x7ffcb1791a3d
74 QQmlBoundSignalExpression::evaluate qqmlboundsignal.cpp 202 0x7ffcb160fad1
75 QQmlBoundSignal_callback qqmlboundsignal.cpp 315 0x7ffcb16100d9
76 QQmlNotifier::emitNotify qqmlnotifier.cpp 71 0x7ffcb180113a
77 QQmlData::signalEmitted qqmlengine.cpp 356 0x7ffcb1673328
78 doActivate<0> qobject.cpp 3913 0x7ffcae56d3b0
79 QMetaObject::activate qobject.cpp 4078 0x7ffcae554408
80 QQmlComponentAttached::completed moc_qqmlcomponentattached_p.cpp 163 0x7ffcb1639f52
81 QQmlObjectCreator::finalize qqmlobjectcreator.cpp 1520 0x7ffcb1804469
82 QQmlComponentPrivate::complete qqmlcomponent.cpp 1149 0x7ffcb16389db
83 QQmlComponentPrivate::completeCreate qqmlcomponent.cpp 1253 0x7ffcb16372db
84 QQmlComponent::completeCreate qqmlcomponent.cpp 1231 0x7ffcb1633e53
85 QQmlComponentPrivate::createWithProperties qqmlcomponent.cpp 959 0x7ffcb16399f5
86 QQmlComponent::create qqmlcomponent.cpp 908 0x7ffcb1633c35
87 QQmlApplicationEnginePrivate::finishLoad qqmlapplicationengine.cpp 135 0x7ffcb15effcb
88 QQmlApplicationEnginePrivate::ensureLoadingFinishes qqmlapplicationengine.cpp 163 0x7ffcb15f026e
89 QQmlApplicationEnginePrivate::startLoad qqmlapplicationengine.cpp 110 0x7ffcb15efa3b
90 QQmlApplicationEngine::load qqmlapplicationengine.cpp 324 0x7ffcb15ee9ae
91 main main.cpp 16 0x7ff6eea1399b
92 qtEntryPoint qtentrypoint_win.cpp 50 0x7ff6eea22107
93 WinMain qtentrypoint_win.cpp 60 0x7ff6eea21f0e
94 invoke_main exe_common.inl 107 0x7ff6eea1ebb2
95 __scrt_common_main_seh exe_common.inl 288 0x7ff6eea1ea9e
96 __scrt_common_main exe_common.inl 331 0x7ff6eea1e95e
97 WinMainCRTStartup exe_winmain.cpp 17 0x7ff6eea1ec4e
98 BaseThreadInitThunk KERNEL32 0x7ffd4a7a7614
99 RtlUserThreadStart ntdll 0x7ffd4bc026b1
- relates to
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- Closed
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