Lmms: LMMS freezes at 100% on export

[ViperZer0]

Bug Summary

LMMS freezes at 100% on any exports that I try. I have tried to export three different projects, one which was new, and two older projects which I know had at one point successfully exported. Each one freezes at 100% and one closes entirely. Running LMMS from a terminal gives me the following error when the freeze/crash happens:
QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'

The project that crashes gives an additional segfault.

Steps to reproduce

• Create any project, the behavior does not seem to be affected at all by the contents of the project.

Expected behavior

Project should export successfully.

Actual behavior

LMMS freezes and sometimes segfaults at 100% exported, throwing the error
QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'

Affected LMMS versions

Version 1.2.2
Arch Linux
JACK Audio

[trebmuh]

I've tried with the demo "CapDan-ReggaeTry".
I've got the same behavior where LMMS doesn't crash, but freezes.

Launched from a terminal, it says the same:
QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'

LMMS 1.2.2, JACK, options:

Note that even if LMMS freezes, the WAV file seems to be correctly exported (ie: I can read it with VLC).

[Spekular]

How long are you waiting to determine that LMMS is frozen? I know on my system, LMMS sometimes sits several seconds at 100% before the export completes.

You mention that you've succesfully exported projects before; what's changed since then? What was the latest configuration that worked?

[trebmuh]

@Spekular I've just run a test for 5 full minutes and it still is frozen.

_Edit: 50 minutes and it sill is frozen. I had to Ctrl-C it._

[Daniele71]

It happens to me too. opensuse TW

[musikBear]

@ViperZer0 & @Daniele71
Are you both on Arch??
We need more information from you @Daniele71 !
I would like you both to try and change the backend to SDL, and retry to export, that way we can point the finger at JACK Audio
Change of backend:
https://lmms.io/wiki/index.php?title=LMMS_Settings#Audio_Settings
If you still freeze we can point at Arch

[Daniele71]

@ViperZer0 & @Daniele71
Are you both on Arch??
We need more information from you @Daniele71 !
I would like you both to try and change the backend to SDL, and retry to export, that way we can point the finger at _JACK Audio_
Change of backend:
https://lmms.io/wiki/index.php?title=LMMS_Settings#Audio_Settings
If you _still_ freeze we can point at Arch

Opensuse Tumbleweed here. It works with SDL backend !

[trebmuh]

Same for me. Tested the export with the SDL backend, then tested with the ALSA backend, that works fine.

[musikBear]

Super! Thank you both @trebmuh & @Daniele71 for your feedback!
This issue is something related to JACK, or a version of JACK.
@trebmuh & @Daniele71
Afaik SDL output is not inferior to JACK, so you should use SDL for now :)

[trebmuh]

You're welcome. If that can help, I'm using a debian 1.9.14~dfsg-1 backport version of JACK2.

[firewall1110]

The same problem is in master (I downloaded&compiled it at 15.09.2020).
Only after export and before freezing message is not:
_QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'_
but (something about this):
_PERFLOG | Project Render | 35.46user, 1.40system 17.39elapsed_

I use Debian Buster : _libjack-jack2-dev 1.9.12~dfsg-2_

P.S.
Terminal output:
_QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'_
is always after rendering - not only in Jack audio device, and after this only with Jack aufio device LMMS freezing. .

[DomClark]

Can someone provide a backtrace of the hang? See https://github.com/LMMS/lmms/wiki/Debugging-LMMS.

[firewall1110]

With stable release (1.2.2) compiled with QT4 i found, that Hung in

void waitUntilRead()
{
    m_writer_sem.acquire( m_size ); /* can not get this line done : but it is QT library call */
    m_writer_sem.release( m_size );
}

//fifo_buffer.h :: line 69

I made some fprintf(stderr, ...) to trace problem with session (last project DnB) exporting mp3 with default setting.
[----] With sdl device:
---- Mixer::stopProcessing():: 0
---- m_fifoWriter
---- m_fifoWriter->finish()
---- fifoWriter::run() -> write( NULL )
m_fifo->available() == True
--FB-- fifoBuffer::waitUntilRead()::m_size == 2 :: have = 2
--FB-- m_writer_sem.acquire( m_size )
--FB-- m_writer_sem.release( m_size )
---- fifoWriter::run() -> waitUntilRead()
---- m_fifoWriter->wait()
---- m_audioDev->stopProcessing()
---- Mixer::stopProcessing():: 1
---- m_fifoWriter == NULL
QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'
--RM-- ~RenderManager()
--M-- restoreAudioDevice()
---- Mixer::stopProcessing():: 2
---- m_fifoWriter == NULL
--M-- stopProcessing()
--RM-- mixer()->restoreAudioDevice()
---- Mixer::stopProcessing():: 3
---- m_fifoWriter
---- m_fifoWriter->finish()
---- fifoWriter::run() -> write( NULL )
m_fifo->available() == True
--FB-- fifoBuffer::waitUntilRead()::m_size == 2 :: have = 1
--FB-- m_writer_sem.acquire( m_size )
--FB-- m_writer_sem.release( m_size )
---- fifoWriter::run() -> waitUntilRead()
---- m_fifoWriter->wait()
---- m_audioDev->stopProcessing()
--RM-- mixer()->changeQuality( m_oldQualitySettings )
---- Mixer::stopProcessing():: 4
---- m_fifoWriter
---- m_fifoWriter->finish()
---- fifoWriter::run() -> write( NULL )
m_fifo->available() == True
--FB-- fifoBuffer::waitUntilRead()::m_size == 2 :: have = 2
--FB-- m_writer_sem.acquire( m_size )
--FB-- m_writer_sem.release( m_size )
---- fifoWriter::run() -> waitUntilRead()
---- m_fifoWriter->wait()
---- m_audioDev->stopProcessing()

[----] With jackd device:
---- Mixer::stopProcessing():: 0
---- m_fifoWriter
---- m_fifoWriter->finish()
---- fifoWriter::run() -> write( NULL )
m_fifo->available() == False
--FB-- fifoBuffer::waitUntilRead()::m_size == 2 :: have = 0
--FB-- m_writer_sem.acquire( m_size )
--FB-- m_writer_sem.release( m_size )
---- fifoWriter::run() -> waitUntilRead()
---- m_fifoWriter->wait()
---- m_audioDev->stopProcessing()
---- Mixer::stopProcessing():: 1
---- m_fifoWriter == NULL
QMetaMethod::invoke: Unable to handle unregistered datatype 'MidiTime'
--RM-- ~RenderManager()
--M-- restoreAudioDevice()
---- Mixer::stopProcessing():: 2
---- m_fifoWriter == NULL
--M-- stopProcessing()
--RM-- mixer()->restoreAudioDevice()
---- Mixer::stopProcessing():: 3
---- m_fifoWriter
---- m_fifoWriter->finish()
---- fifoWriter::run() -> write( NULL )
m_fifo->available() == True
--FB-- fifoBuffer::waitUntilRead()::m_size == 2 :: have = 1

[Actual files are: fifo_buffer.h , Mixer.cpp , RenderManager.cpp ]

[firewall1110]

I found more bugs in rendering:

the same is in portaudio device:
[using direct sound card name:]
[lmms_portaudio.txt](https://github.com/LMMS/lmms/files/5244438/lmms_portaudio.txt)
[using oss "virtual" device:]
[lmms_portaudio_oss.txt](https://github.com/LMMS/lmms/files/5244454/lmms_portaudio_oss.txt)

But with soundio device there is SegFault on export start (exception with compiled version, but infinite loop with AppImage 1.2.2):
lmms_soundio_dummy.txt
lmms_soundio_pulse.txt

P.S.
All bugs are both in stable and master versions (in lmms-1.2.2-linux-x86_64.AppImage I can not set direct sound card with portaudio - no sound).

[firewall1110]

I clear this:
lmms_jackd_freeze_gdb.txt

But I think it is not more actual ...

[firewall1110]

This bug is related to https://github.com/LMMS/lmms/issues/2638

[Thank You, PhysSong !]

_This can be formulated:_

Some (playable) devices have problems in Mixer::stopProcessing():
soundio : Segmentation Fault

jackd and (sometimes) portaudio :
no sound after Mixer::stopProcessing() , Mixer::startProcessing() ;
and hung in next Mixer::stopProcessing() .

P.S.

_In my experiment I replaced_
void Mixer::restoreAudioDevice()
_and_
void Mixer::changeQuality( const struct qualitySettings & _qs )

_with_

void Mixer::restoreAudioDeviceWithQuality( const struct qualitySettings & _qs )

_In original code_
Mixer::stopProcessing() //<- befor rendering (export)
and
Mixer::startProcessing() ; Mixer::stopProcessing() ; Mixer::startProcessing() ;
after rendering (export)

[firewall1110]

Sorry for my mistake ...

soundio crash with segmentation Fault in Mixer::startProcessing() ;

but problem is in Mixer::stopProcessing()

Line in AudioSoundIo.cpp:
void AudioSoundIo::stopProcessing()
{
m_stopped = true;
if (m_outstream)
{
soundio_outstream_destroy(m_outstream);
// line 228 :: after this we can not simply soundio_outstream_start(m_outstream)) - Segmantation Fault!
m_outstream = NULL; // Segmantation Fault in every conditions
}

if (m_outBuf)
{
    delete[] m_outBuf;
    m_outBuf = NULL;
}

}

[firewall1110]

It seems that this bug can be fixed by adding only one line:

void AudioJack::startProcessing()
{
    if( m_active || m_client == NULL )
    {
        m_stopped = false; // Only this should be added
        return;
    }
...
}

Patch file:

lmms_5664.diff.zip

But I have one pending PR ...

[qnebra]

It doesn't matter how many pull requests you had open. Made new PR if it fixes issue.

[firewall1110]

It seems that I instead have added change to my pending PR ...
Is it problem?

[PhysSong]

Not that much at this moment. We can split them before merging if we should.

[firewall1110]

I think it would be better to work with them both (_not_ splitting): second change is too small - only 1 line.

[firewall1110]

PR patch against stable LMMS 1.2.2 :
lmms_1_2_2_stable.patch.gz

[DomClark]

Fixed in #5681.

[trebmuh]

Awesome.
Thank you all.