QAudioOutput and QAudioInput on linux with ALSA
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Hello,
I'm writing a simple VoIP application, and by now it runs very well on Windows, while on Linux (I'm using 3.18.6-1-ARCH, gcc 4.9.2) I have no choice but build it against Qt5, start the PulseAudio daemon, and select the devices shown in this picture, otherwise as soon as I do some UI interaction it soon crashes.
If I use QAudioOutput in "push mode", I get SIGSEGV when I write to the QIODevice returned by QAudioOutput::start(), at this line:m_pushoutput->write(m_pushbuff.constData(), len);in the audiooutpanel.cpp file (line 312);
if I use QAudioOutput in "pull mode", after a while the application freezes.I further investigated, compiled a debug version of Qt 4.8.6, and found that, when the system sends SIGSGV, the debugger stops at this line:
int space = bytesFree();in the QAudioOutputPrivate::write function of the qaudiooutput_alsa_p.cpp file of the qt 4.8.6 source (11 lines below):
qint64 QAudioOutputPrivate::write( const char *data, qint64 len ) { // Write out some audio data if ( !handle ) return 0; #ifdef DEBUG_AUDIO qDebug()<<"frames to write out = "<< snd_pcm_bytes_to_frames( handle, (int)len )<<" ("<<len<<") bytes"; #endif int frames, err; int space = bytesFree(); if(len < space) { // Just write it frames = snd_pcm_bytes_to_frames( handle, (int)len ); err = snd_pcm_writei( handle, data, frames ); } else { // Only write space worth frames = snd_pcm_bytes_to_frames( handle, (int)space ); err = snd_pcm_writei( handle, data, frames ); } if(err > 0) { totalTimeValue += err; resuming = false; errorState = QAudio::NoError; if (deviceState != QAudio::ActiveState) { deviceState = QAudio::ActiveState; emit stateChanged(deviceState); } return snd_pcm_frames_to_bytes( handle, err ); } else err = xrun_recovery(err); if(err < 0) { close(); errorState = QAudio::FatalError; deviceState = QAudio::StoppedState; emit stateChanged(deviceState); } return 0; }Thanks for any help.
PS: also I don't seem to find a way to succesfully build qt 4.8.6 with full PulseAudio support as QAudioDeviceInfo::availableDevices only returns two items ("system default" and "default"); this is the last configuration I've tryed:
./configure -platform linux-g++ -static -debug -prefix /home/tilly/BIN/qt-4.8.6-debug -qt-sql-sqlite -multimedia -audio-backend -system-nas-sound -no-openssl -no-qt3support -no-xmlpatterns -no-webkit -no-javascript-jit -no-script -no-scripttools -no-declarative -no-declarative-debug -no-nis -no-cups -nomake demos -nomake examples -nomake tools -
Hi and welcome to devnet,
Do you have the PulseAudio development package installed ? You can also run configure with the -v option to see why the detection fails.
As for the crashes, can you run your application with a debug build ?
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Hi, thank you for your quick and kind reply :)
I've run configure with the -v option, this is the output as for PulseAudio:
PulseAudio auto-detection... () g++ -c -pipe -D_REENTRANT -g -Wall -W -I../../../mkspecs/linux-g++ -I. -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -o pulseaudio.o pulseaudio.cpp g++ -Wl,-rpath,/home/tilly/BIN/qt-4.8.6-debug/lib -o pulseaudio pulseaudio.o -lpulse-mainloop-glib -lpulse -lglib-2.0 PulseAudio enabled.So it seems it's been detected.
I'm not aware of any PulseAudio development package on ARCH linux, anyway I checked that the folder /usr/include/pulse is present in my system, and contains the pulseaudio header files, but I don't know if this is sufficient. Should I download something else?As for the crashes, yes I run the app with the debug build (of Qt, right?) and, as I wrote, while with the release build I got stuck in the
m_pushoutput->write(m_pushbuff.constData(), len);line of my code (where m_pushoutput is the QIODevice returned by calling QAudioOutput::start()), with the debug build the SIGSEGV is emitted at this line:
int space = bytesFree();in the qaudiooutput_alsa_p.cpp file of the qt 4.8.6 sources.
To be more precise crashes happens randomly, for example, right after I click on a combo (before changing selection), when both audioinput and adiooutput are processing audio. The same thing (even worst) happens with Qt5, but in that case, when I select the "alsa_input" and "alsa_output" devices as shown here, it runs smoothly.
As it stops before entering the bytesAvailable() function, it looks like a stack overflow or something, but I don't know how to further investigate.
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To look a bit further down, run a debug build of Qt and your software so you can grab some more information
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Dear SGainst, I did run a debug build of Qt (v4.8.6) and my software, and found that where the program crashes each time is at this instruction at line 525 of the qtaudiooutput_pulse_p.cpp Qt 4.8.6 source file:
int space = bytesFree();that is found inside this function (10 lines below definition):
qint64 QAudioOutputPrivate::write( const char *data, qint64 len ) { // Write out some audio data if ( !handle ) return 0; #ifdef DEBUG_AUDIO qDebug()<<"frames to write out = "<< snd_pcm_bytes_to_frames( handle, (int)len )<<" ("<<len<<") bytes"; #endif int frames, err; int space = bytesFree(); if(len < space) { // Just write it frames = snd_pcm_bytes_to_frames( handle, (int)len ); err = snd_pcm_writei( handle, data, frames ); } else { // Only write space worth frames = snd_pcm_bytes_to_frames( handle, (int)space ); err = snd_pcm_writei( handle, data, frames ); } if(err > 0) { totalTimeValue += err; resuming = false; errorState = QAudio::NoError; if (deviceState != QAudio::ActiveState) { deviceState = QAudio::ActiveState; emit stateChanged(deviceState); } return snd_pcm_frames_to_bytes( handle, err ); } else err = xrun_recovery(err); if(err < 0) { close(); errorState = QAudio::FatalError; deviceState = QAudio::StoppedState; emit stateChanged(deviceState); } return 0; }Since there are no variables read/write/dereferencing at that point, I thought it can probably be a stack overflow(?), but I don't actually know how to interpret/fix this. Here's the Disassembler view at eip:
516 [1] { 0x80be742 55 push %ebp 0x80be743 <+0x0001> 89 e5 mov %esp,%ebp 0x80be745 <+0x0003> 57 push %edi 0x80be746 <+0x0004> 56 push %esi 0x80be747 <+0x0005> 53 push %ebx 0x80be748 <+0x0006> 83 ec 2c sub $0x2c,%esp 0x80be74b <+0x0009> e8 a0 45 f9 ff call 0x8052cf0 <__x86.get_pc_thunk.bx> 0x80be750 <+0x000e> 81 c3 ac 57 e2 00 add $0xe257ac,%ebx 0x80be756 <+0x0014> 8b 45 10 mov 0x10(%ebp),%eax 0x80be759 <+0x0017> 89 45 d0 mov %eax,-0x30(%ebp) 0x80be75c <+0x001a> 8b 45 14 mov 0x14(%ebp),%eax 0x80be75f <+0x001d> 89 45 d4 mov %eax,-0x2c(%ebp) 518 [1] if ( !handle ) 0x80be762 <+0x0020> 8b 45 08 mov 0x8(%ebp),%eax 0x80be765 <+0x0023> 8b 40 78 mov 0x78(%eax),%eax 0x80be768 <+0x0026> 85 c0 test %eax,%eax 0x80be76a <+0x0028> 75 0f jne 0x80be77b <QAudioOutputPrivate::write(char const*, long long)+57> 519 [1] return 0; 0x80be76c <+0x002a> b8 00 00 00 00 mov $0x0,%eax 0x80be771 <+0x002f> ba 00 00 00 00 mov $0x0,%edx 0x80be776 <+0x0034> e9 65 01 00 00 jmp 0x80be8e0 <QAudioOutputPrivate::write(char const*, long long)+414> 525 [1] int space = bytesFree(); 0x80be77b <+0x0039> 8b 45 08 mov 0x8(%ebp),%eax 0x80be77e <+0x003c> 8b 00 mov (%eax),%eax 0x80be780 <+0x003e> 83 c0 44 add $0x44,%eax 0x80be783 <+0x0041> 8b 00 mov (%eax),%eax 0x80be785 <+0x0043> 83 ec 0c sub $0xc,%esp 0x80be788 <+0x0046> ff 75 08 pushl 0x8(%ebp) 0x80be78b <+0x0049> ff d0 call *%eax 0x80be78d <+0x004b> 83 c4 10 add $0x10,%esp 0x80be790 <+0x004e> 89 45 e0 mov %eax,-0x20(%ebp) 526 [1] if(len < space) { 0x80be793 <+0x0051> 8b 45 e0 mov -0x20(%ebp),%eax 0x80be796 <+0x0054> 99 cltd 0x80be797 <+0x0055> 3b 55 d4 cmp -0x2c(%ebp),%edx 0x80be79a <+0x0058> 7c 41 jl 0x80be7dd <QAudioOutputPrivate::write(char const*, long long)+155> 0x80be79c <+0x005a> 3b 55 d4 cmp -0x2c(%ebp),%edx 0x80be79f <+0x005d> 7f 05 jg 0x80be7a6 <QAudioOutputPrivate::write(char const*, long long)+100> 0x80be7a1 <+0x005f> 3b 45 d0 cmp -0x30(%ebp),%eax 0x80be7a4 <+0x0062> 76 37 jbe 0x80be7dd <QAudioOutputPrivate::write(char const*, long long)+155> 528 [1] frames = snd_pcm_bytes_to_frames( handle, (int)len ); 0x80be7a6 <+0x0064> 8b 55 d0 mov -0x30(%ebp),%edx 0x80be7a9 <+0x0067> 8b 45 08 mov 0x8(%ebp),%eax 0x80be7ac <+0x006a> 8b 40 78 mov 0x78(%eax),%eax 0x80be7af <+0x006d> 83 ec 08 sub $0x8,%esp 0x80be7b2 <+0x0070> 52 push %edx 0x80be7b3 <+0x0071> 50 push %eax 0x80be7b4 <+0x0072> e8 e7 22 f9 ff call 0x8050aa0 <snd_pcm_bytes_to_frames@plt> 0x80be7b9 <+0x0077> 83 c4 10 add $0x10,%esp 0x80be7bc <+0x007a> 89 45 dc mov %eax,-0x24(%ebp) 529 [1] err = snd_pcm_writei( handle, data, frames ); 0x80be7bf <+0x007d> 8b 55 dc mov -0x24(%ebp),%edx 0x80be7c2 <+0x0080> 8b 45 08 mov 0x8(%ebp),%eax 0x80be7c5 <+0x0083> 8b 40 78 mov 0x78(%eax),%eax 0x80be7c8 <+0x0086> 83 ec 04 sub $0x4,%esp 0x80be7cb <+0x0089> 52 push %edx 0x80be7cc <+0x008a> ff 75 0c pushl 0xc(%ebp) 0x80be7cf <+0x008d> 50 push %eax 0x80be7d0 <+0x008e> e8 1b 18 f9 ff call 0x804fff0 <snd_pcm_writei@plt> 0x80be7d5 <+0x0093> 83 c4 10 add $0x10,%esp 0x80be7d8 <+0x0096> 89 45 e4 mov %eax,-0x1c(%ebp) 0x80be7db <+0x0099> eb 34 jmp 0x80be811 <QAudioOutputPrivate::write(char const*, long long)+207> 532 [1] frames = snd_pcm_bytes_to_frames( handle, (int)space ); 0x80be7dd <+0x009b> 8b 45 08 mov 0x8(%ebp),%eax 0x80be7e0 <+0x009e> 8b 40 78 mov 0x78(%eax),%eax 0x80be7e3 <+0x00a1> 83 ec 08 sub $0x8,%esp 0x80be7e6 <+0x00a4> ff 75 e0 pushl -0x20(%ebp) 0x80be7e9 <+0x00a7> 50 push %eax 0x80be7ea <+0x00a8> e8 b1 22 f9 ff call 0x8050aa0 <snd_pcm_bytes_to_frames@plt> 0x80be7ef <+0x00ad> 83 c4 10 add $0x10,%esp 0x80be7f2 <+0x00b0> 89 45 dc mov %eax,-0x24(%ebp) 533 [1] err = snd_pcm_writei( handle, data, frames ); 0x80be7f5 <+0x00b3> 8b 55 dc mov -0x24(%ebp),%edx 0x80be7f8 <+0x00b6> 8b 45 08 mov 0x8(%ebp),%eax 0x80be7fb <+0x00b9> 8b 40 78 mov 0x78(%eax),%eax 0x80be7fe <+0x00bc> 83 ec 04 sub $0x4,%esp 0x80be801 <+0x00bf> 52 push %edx 0x80be802 <+0x00c0> ff 75 0c pushl 0xc(%ebp) 0x80be805 <+0x00c3> 50 push %eax 0x80be806 <+0x00c4> e8 e5 17 f9 ff call 0x804fff0 <snd_pcm_writei@plt> 0x80be80b <+0x00c9> 83 c4 10 add $0x10,%esp 0x80be80e <+0x00cc> 89 45 e4 mov %eax,-0x1c(%ebp) 535 [1] if(err > 0) { 0x80be811 <+0x00cf> 83 7d e4 00 cmpl $0x0,-0x1c(%ebp) 0x80be815 <+0x00d3> 7e 6d jle 0x80be884 <QAudioOutputPrivate::write(char const*, long long)+322> 536 [1] totalTimeValue += err; 0x80be817 <+0x00d5> 8b 45 08 mov 0x8(%ebp),%eax 0x80be81a <+0x00d8> 8b 70 28 mov 0x28(%eax),%esi 0x80be81d <+0x00db> 8b 78 2c mov 0x2c(%eax),%edi 0x80be820 <+0x00de> 8b 45 e4 mov -0x1c(%ebp),%eax 0x80be823 <+0x00e1> 99 cltd 0x80be824 <+0x00e2> 01 f0 add %esi,%eax 0x80be826 <+0x00e4> 11 fa adc %edi,%edx 0x80be828 <+0x00e6> 8b 4d 08 mov 0x8(%ebp),%ecx 0x80be82b <+0x00e9> 89 41 28 mov %eax,0x28(%ecx) 0x80be82e <+0x00ec> 89 51 2c mov %edx,0x2c(%ecx) 537 [1] resuming = false; 0x80be831 <+0x00ef> 8b 45 08 mov 0x8(%ebp),%eax 0x80be834 <+0x00f2> c6 40 1a 00 movb $0x0,0x1a(%eax) 538 [1] errorState = QAudio::NoError; 0x80be838 <+0x00f6> 8b 45 08 mov 0x8(%ebp),%eax 0x80be83b <+0x00f9> c7 40 10 00 00 00 00 movl $0x0,0x10(%eax) 539 [1] if (deviceState != QAudio::ActiveState) { 0x80be842 <+0x0100> 8b 45 08 mov 0x8(%ebp),%eax 0x80be845 <+0x0103> 8b 40 14 mov 0x14(%eax),%eax 0x80be848 <+0x0106> 85 c0 test %eax,%eax 0x80be84a <+0x0108> 74 20 je 0x80be86c <QAudioOutputPrivate::write(char const*, long long)+298> 540 [1] deviceState = QAudio::ActiveState; 0x80be84c <+0x010a> 8b 45 08 mov 0x8(%ebp),%eax 0x80be84f <+0x010d> c7 40 14 00 00 00 00 movl $0x0,0x14(%eax) 541 [1] emit stateChanged(deviceState); 0x80be856 <+0x0114> 8b 45 08 mov 0x8(%ebp),%eax 0x80be859 <+0x0117> 8b 50 14 mov 0x14(%eax),%edx 0x80be85c <+0x011a> 8b 45 08 mov 0x8(%ebp),%eax 0x80be85f <+0x011d> 83 ec 08 sub $0x8,%esp 0x80be862 <+0x0120> 52 push %edx 0x80be863 <+0x0121> 50 push %eax 0x80be864 <+0x0122> e8 a1 35 00 00 call 0x80c1e0a <QAbstractAudioOutput::stateChanged(QAudio::State)> 0x80be869 <+0x0127> 83 c4 10 add $0x10,%esp 543 [1] return snd_pcm_frames_to_bytes( handle, err ); 0x80be86c <+0x012a> 8b 45 08 mov 0x8(%ebp),%eax 0x80be86f <+0x012d> 8b 40 78 mov 0x78(%eax),%eax 0x80be872 <+0x0130> 83 ec 08 sub $0x8,%esp 0x80be875 <+0x0133> ff 75 e4 pushl -0x1c(%ebp) 0x80be878 <+0x0136> 50 push %eax 0x80be879 <+0x0137> e8 42 43 f9 ff call 0x8052bc0 <snd_pcm_frames_to_bytes@plt> 0x80be87e <+0x013c> 83 c4 10 add $0x10,%esp 0x80be881 <+0x013f> 99 cltd 0x80be882 <+0x0140> eb 5c jmp 0x80be8e0 <QAudioOutputPrivate::write(char const*, long long)+414> 545 [1] err = xrun_recovery(err); 0x80be884 <+0x0142> 83 ec 08 sub $0x8,%esp 0x80be887 <+0x0145> ff 75 e4 pushl -0x1c(%ebp) 0x80be88a <+0x0148> ff 75 08 pushl 0x8(%ebp) 0x80be88d <+0x014b> e8 b4 e3 ff ff call 0x80bcc46 <QAudioOutputPrivate::xrun_recovery(int)> 0x80be892 <+0x0150> 83 c4 10 add $0x10,%esp 0x80be895 <+0x0153> 89 45 e4 mov %eax,-0x1c(%ebp) 547 [1] if(err < 0) { 0x80be898 <+0x0156> 83 7d e4 00 cmpl $0x0,-0x1c(%ebp) 0x80be89c <+0x015a> 79 38 jns 0x80be8d6 <QAudioOutputPrivate::write(char const*, long long)+404> 548 [1] close(); 0x80be89e <+0x015c> 83 ec 0c sub $0xc,%esp 0x80be8a1 <+0x015f> ff 75 08 pushl 0x8(%ebp) 0x80be8a4 <+0x0162> e8 3f fd ff ff call 0x80be5e8 <QAudioOutputPrivate::close()> 0x80be8a9 <+0x0167> 83 c4 10 add $0x10,%esp 549 [1] errorState = QAudio::FatalError; 0x80be8ac <+0x016a> 8b 45 08 mov 0x8(%ebp),%eax 0x80be8af <+0x016d> c7 40 10 04 00 00 00 movl $0x4,0x10(%eax) 550 [1] deviceState = QAudio::StoppedState; 0x80be8b6 <+0x0174> 8b 45 08 mov 0x8(%ebp),%eax 0x80be8b9 <+0x0177> c7 40 14 02 00 00 00 movl $0x2,0x14(%eax) 551 [1] emit stateChanged(deviceState); 0x80be8c0 <+0x017e> 8b 45 08 mov 0x8(%ebp),%eax 0x80be8c3 <+0x0181> 8b 50 14 mov 0x14(%eax),%edx 0x80be8c6 <+0x0184> 8b 45 08 mov 0x8(%ebp),%eax 0x80be8c9 <+0x0187> 83 ec 08 sub $0x8,%esp 0x80be8cc <+0x018a> 52 push %edx 0x80be8cd <+0x018b> 50 push %eax 0x80be8ce <+0x018c> e8 37 35 00 00 call 0x80c1e0a <QAbstractAudioOutput::stateChanged(QAudio::State)> 0x80be8d3 <+0x0191> 83 c4 10 add $0x10,%esp 553 [1] return 0; 0x80be8d6 <+0x0194> b8 00 00 00 00 mov $0x0,%eax 0x80be8db <+0x0199> ba 00 00 00 00 mov $0x0,%edx 554 [1] } 0x80be8e0 <+0x019e> 8d 65 f4 lea -0xc(%ebp),%esp 0x80be8e3 <+0x01a1> 5b pop %ebx 0x80be8e4 <+0x01a2> 5e pop %esi 0x80be8e5 <+0x01a3> 5f pop %edi 0x80be8e6 <+0x01a4> 5d pop %ebp 0x80be8e7 <+0x01a5> c3 retCan anyone explain/suggest a fix for that?
Thanks a lot in advance -
Can you redo the build with DEBUG_AUDIO defined ? It might give some additional hints on what is going on
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Hi, here we go :)
After compiling with DEBUG_AUDIO I run the app, and got a long list of logs of what's appening, just before the app stops or hungs:
37 s 236 ms :open() 37 s 359 ms :open() defaults out of range pmin= 21333 , pmax= 21334 , bmin= 42666 , bmax= 170667 used: buffer_time= 85332 , period_time= 21333 37 s 457 ms :userFeed() IN read in bytes = 0 (frames=0) 37 s 460 ms :userFeed() OUT frames to write out = 512 ( 1024 ) bytes 37 s 478 ms :updateAvailable() frames to write out = 512 ( 1024 ) bytes frames to write out = 512 ( 1024 ) bytes frames to write out = 512 ( 1024 ) bytes 37 s 503 ms :updateAvailable() 37 s 509 ms :userFeed() OUT 37 s 524 ms :updateAvailable() 37 s 541 ms :updateAvailable() 37 s 544 ms :userFeed() IN 37 s 565 ms :updateAvailable() 37 s 566 ms :updateAvailable() read in bytes = 1700 (frames=850) frames to write to QIODevice = 850 ( 1700 ) bytes frames to write out = 512 ( 1024 ) bytes 37 s 683 ms :updateAvailable() ... (long long list of similar logs) ... frames to write out = 512 ( 1024 ) bytes frames to write out = 512 ( 1024 ) bytes 39 s 10 ms :updateAvailable() 39 s 11 ms :userFeed() OUT 39 s 22 ms :updateAvailable() 39 s 26 ms :userFeed() OUT 39 s 36 ms :userFeed() IN read in bytes = 680 (frames=340) frames to write to QIODevice = 340 ( 680 ) bytes 39 s 44 ms :updateAvailable() 39 s 47 ms :userFeed() OUT frames to write out = 512 ( 1024 ) bytes frames to write out = 512 ( 1024 ) bytes frames to write out = 512 ( 1024 ) bytes 39 s 66 ms :updateAvailable() 39 s 68 ms :userFeed() OUT 39 s 86 ms :updateAvailable() 39 s 89 ms :userFeed() IN read in bytes = 1020 (frames=510) frames to write to QIODevice = 510 ( 1020 ) bytes 39 s 99 ms :userFeed() OUT 39 s 116 ms :updateAvailable() 39 s 117 ms :userFeed() OUT frames to write out = 512 ( 1024 ) bytes frames to write out = 512 ( 1024 ) bytesActually I didn't find this very usefull, but if you wish I can send more and give you a more detailed description.
What I've found really strange (I'm not used to read assembly at all) is that when the SIGSEGV occurs the eip points at line 0x80be783 in this fragment (4th line down):
525 [1] int space = bytesFree(); 0x80be77b <+0x0039> 8b 45 08 mov 0x8(%ebp),%eax 0x80be77e <+0x003c> 8b 00 mov (%eax),%eax 0x80be780 <+0x003e> 83 c0 44 add $0x44,%eax 0x80be783 <+0x0041> 8b 00 mov (%eax),%eax 0x80be785 <+0x0043> 83 ec 0c sub $0xc,%esp 0x80be788 <+0x0046> ff 75 08 pushl 0x8(%ebp) 0x80be78b <+0x0049> ff d0 call *%eax 0x80be78d <+0x004b> 83 c4 10 add $0x10,%esp 0x80be790 <+0x004e> 89 45 e0 mov %eax,-0x20(%ebp) (see entire fragment in my previous answer)this seems to be a push in the stack just before calling "bytesFree()".
But why is deferencing %eax and than calling *%eax is behond my understanding (in all other function call there is a fixed memory address).
The really strange thing, hower, is that if I watch locals at that point:int frames, err; int space = bytesFree(); <-- stopped herewhile when stopped at breakpoint "frames", "err" and "space" contain just rubbish, as expected, when stopped after SIGSEGV they do have initialized values (usually frames=1, err=-77, space=320). Does this make any sense??
However, as it seems that the device is stopped from some other thread while inside this function, I've slightly modified the qaudiooutput_asla_p.cpp Qt source file, and added a few checks just before trying to write to the audio device;
here's the pach:522,525d519 < // tilly 20/04/2015: moved this two lines on top of function) < if(deviceState != QAudio::ActiveState && deviceState != QAudio::IdleState) < return 0; < 529,530c523,524 < // tilly 20/04/2015: (see above) < --- > if(deviceState != QAudio::ActiveState && deviceState != QAudio::IdleState) > return 0; 540,543d533 < // tilly 20/04/2015: added this two lines to check state before SIGEGV occurs! < if(deviceState != QAudio::ActiveState && deviceState != QAudio::IdleState) < return 0; < 784,787d773 < // tilly 20/04/2015: added this two lines < if(!audioDevice) < return 0; < 792c778 < while(audioDevice && (written < len)) { // tilly 20/04/2015: added audioDevice test! --- > while(written < len) { 796,797c782 < else // tilly 20/04/2015: added else [if ever chunk<0 (as not excluded by the test before) - adding to written would result in a mess probably..] < written+=chunk; --- > written+=chunk;As I link to Qt statically, this gave my app a reasonable level of stability, so if audio stops I can just print an error message, but any further explaination on the cause of the SIGSEGV would be much appreciated.
What do you think about that? -
I'd check with all function modifying the state of the device to see if there's something unusual happening. Also I wonder if it's your device driver that is acting up.
A quick check to the bug report system would also be a good idea
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