Echo effect causes distortion when active with other effects

[tbazant]

Bug Description

Hi!
I have a Numark NS4FX controller and when playing via the integrated audio interface (haven't tested with external one), ECHO in combination with REVERB or FLANGER plays fine for a few seconds and then the sound turns to ugly loud distorted noise until I turn ECHO off.

Version

2.6 beta, compiled

OS

Debian stable 13

[ronso0]

I use Echo all the time and I don't notice any issues (single or on conjunction with Moog Filter or Reverb)

Could that be a Flanger issue?

[acolombier]

I often use echo and can confirm I sometime gets weird glitches when used with other effect in chain, more likes "ticks" than distortion tho. What's strange is that this isn't consistent and often gets fixed with a reboot.

[daschuer]

From my general experience these "ticks" are caused by missing ramping. This is independent from effect chaining, and is notable dependent on the moment in the music it happens.
The "reboot fix" nature sound more like an uninitialized buffer, or an out of bound access where the uninitialized memory that is used changes during booting.
The "ugly loud distorted noise until I turn ECHO" seems to be a third issue with a feedback loop of the echo.

I can confirm the ticks and the loud noise with a feedback loop:

with these settings:

[tbazant]

latest observation. the distorted behaviour appeard when i'm using the integrated NS4FX audio interface. when i switch to external MAYA44, this does not happen. BTW my audio buffer is 11.6ms

[daschuer]

That sounds more like a clipping issue. The echo effect is able to double up the signal above the clipping threshold. The mixxx engine itself has a floating point format, and can handle any value. There should be a clipping stage at the output, so the hardware should make no difference.
As it makes a difference anyway, there must be a bug.

[acolombier]

The "reboot fix" nature sound more like an uninitialized buffer, or an out of bound access where the uninitialized memory that is used changes during booting.

Yeah, I though as much, but couldn't spot any obvious one, tho I am not so familiar with this part of the code base so could have missed it!
Thanks for confirming tho. Do you think we should create individual bug reports?

[daschuer]

I don't mind. We have three issue.

• Missing ramping
• Reboot issue
• Clipping issue.

[myCatnip]

Reverb Echo Filter chain (top to bottom). Turn on echo, sound cuts out (with a click, or sometimes almost sounds like white noise but more painful). Doesn't matter what latency, from 1.6 to 80ms (i was on 5ms when i try this, and i changed after getting sound back higher and higher and it kept happening.

I just tested 4deck 4fx all fx on every deck.. with that echo chain and another echo chain... everything going happily with the other echo chain... at 1.67ms latency (was just curious.. i know i get warnings now and then at 1.6ms, every other test is at 5ms+)...so everything is going fine, all 4 fx units on, all 4 decks, playing with knobs, eqs, echo chain going... only that Echo is off in that chain. Turn it on... bam within a moment no sound.

Then it gets wierder. I threw in random FX chains to FX3 and FX4 for this test, FX4 contained BQ EQ Reverb Balance. I was trying to get sound back, turning off everything. I turn off a lot, nothing. I turn off balance in that FX4 chain. I get sound back in just the left channel. Toggling that balance in FX4 would turn on and off the left channel.

The balance was not altered, this left audio only is curious because that's exactly how it would most often cut out, to just left channel having audio, in my usual simple setup. Also it has never cut out to just right audio. Usually just left, sometimes none.

Normally i'm using 2 decks 2fx. First noticed this echo issue when i have FX1 on (Flange Bitcrusher Filterr chain) then i add in FX 2 to that deck, and when echo is turned on, sound cuts out, usually just right channel, but can also be both. I turn off echo, but sound only comes back when I turn the filter knob a bit (on FX2).

I got the issue to happen in developer mode twice just now, and nothing in the logs.

I am on a real time Kernel 6.12 (this happens on 6.17 rt also). I made this switch to real time exactly because I was experiencing a lot of random clickynesss at every latency and thought RT might help, but i haven't checked anything about my real time setutp; if i'm even set up correctly for rt, because I thought the issue went away, so i saw no reason to check, however I've just realised... the problem might have just gone away because I haven't turned on Echo in that chain since switching Kernel to "solve" this issue.

Just giving this info FWIW. This particular chain and setup on 6.12 real time is a very repeatable issue for me. My current solution is not using the echo.

Oh this was happening both in 2.5.4 (now) and 2.5.3 recently.

I just saw: trl 0x2E, val 0x7F"
debug [Main] Processing QEvent::MetaCall for object WaveformWidgetFactory(0x58873bdd9f60) running in thread: "Main" took 383 ms

and I'm just typing here sitting at 0.5% cpu usage and 0% gpu usage... maybe real time was a bad idea and the issue is just the echo.

Will test with non RT kernel tomorrow.

[ronso0]

Thanks for the info!

FWIW just recently I experimented with some Quick Effect chains, and with one that has Echo I also suddenly got insane noise on that channel. I didn't check which chain exactly that was, but I used it before a few tiumes without any issues 🤷‍♂️

[acolombier]

It looks like Echo has an OOB read. I am struggling to get the sanitizer working, and the crash only trigger and Android, but I assume this is a global problem, which could explain or be related to the issue we hearing

F/DEBUG   (20875): Cmdline: org.mixxx
F/DEBUG   (20875): pid: 20151, tid: 20226, name: AudioTrack  >>> org.mixxx <<<
F/DEBUG   (20875): uid: 10302
F/DEBUG   (20875): tagged_addr_ctrl: 0000000000000001 (PR_TAGGED_ADDR_ENABLE)
F/DEBUG   (20875): pac_enabled_keys: 000000000000000f (PR_PAC_APIAKEY, PR_PAC_APIBKEY, PR_PAC_APDAKEY, PR_PAC_APDBKEY)
F/DEBUG   (20875): esr: 0000000092000007 (Data Abort Exception 0x24)
F/DEBUG   (20875): signal 11 (SIGSEGV), code 2 (SEGV_ACCERR), fault addr 0xb4000070767c4000 (read)
F/DEBUG   (20875):     x0  00000000002327fc  x1  0000000000000800  x2  b400007263ddd310  x3  b4000072641bd6f0
F/DEBUG   (20875):     x4  000000709f63e628  x5  0000000000000001  x6  0000000000000263  x7  000000000000366d
F/DEBUG   (20875):     x8  000000000008ca00  x9  0000000000000132  x10 0000000000000264  x11 0000000000005064
F/DEBUG   (20875):     x12 b400007076591800  x13 000000000008c9fd  x14 0000000000002832  x15 b400007076591804
F/DEBUG   (20875):     x16 0000000000000002  x17 000000000008c9ff  x18 000000709ee20000  x19 b400007295949350
F/DEBUG   (20875):     x20 000000709f63f640  x21 0000000000005065  x22 b400007233f78810  x23 000000709f63e628
F/DEBUG   (20875):     x24 0000000000000001  x25 b4000072641bd6f0  x26 b4000073448da8e0  x27 b40000722c63de38
F/DEBUG   (20875):     x28 000000709f63f640  x29 b40000722c67ab80
F/DEBUG   (20875):     lr  00000070e27c9ab8  sp  000000709f63e5b0  pc  00000070e27c9cd8  pst 0000000020001000
F/DEBUG   (20875):     esr 0000000092000007
F/DEBUG   (20875): 35 total frames
F/DEBUG   (20875): backtrace:
F/DEBUG   (20875):       #00 pc 0000000000e7dcd8  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (EchoEffect::processChannel(EchoGroupState*, float const*, float*, mixxx::EngineParameters const&, EffectEnableState, GroupFeatureState const&)+684) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #01 pc 0000000000ecec9c  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (EngineEffect::process(ChannelHandle const&, ChannelHandle const&, float const*, float*, unsigned long, mixxx::audio::SampleRate, EffectEnableState, GroupFeatureState const&)+832) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #02 pc 0000000000ed0db8  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (EngineEffectChain::process(ChannelHandle const&, ChannelHandle const&, float*, float*, unsigned long, mixxx::audio::SampleRate,GroupFeatureState const&, bool)+564) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #03 pc 0000000000ed2120  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (EngineEffectsManager::processInner(SignalProcessingStage, ChannelHandle const&, ChannelHandle const&, float*, float*, unsigned long, mixxx::audio::SampleRate, GroupFeatureState const&, float, float, bool)+412) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #04 pc 0000000000ed22d8  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (EngineEffectsManager::processPostFaderInPlace(ChannelHandle const&, ChannelHandle const&, float*, unsigned long, mixxx::audio::SampleRate, GroupFeatureState const&, float, float, bool)+48) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #05 pc 0000000000edd3f4  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (ChannelMixer::applyEffectsInPlaceAndMixChannels(EngineMixer::GainCalculator const&, QVarLengthArray<EngineMixer::ChannelInfo*, 64ll> const&, QVarLengthArray<EngineMixer::GainCache, 64ll>*, float*, ChannelHandle const&, unsigned long, mixxx::audio::SampleRate, EngineEffectsManager*)+320) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #06 pc 0000000000edaab4  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (EngineMixer::process(unsigned long)+1100) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #07 pc 00000000012ec1d4  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (SoundDevicePortAudio::callbackProcessClkRef(long, float*, float const*, PaStreamCallbackTimeInfo const*, unsigned long)+940) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #08 pc 0000000002123f54  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (NonAdaptingProcess+1092) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)
F/DEBUG   (20875):       #09 pc 00000000021239fc  /data/app/~~lCyqHBJ7IsEF0UGONuHTdg==/org.mixxx-dBMi-9NmqIXf0fJDq5ddCw==/lib/arm64/libmixxx_arm64-v8a.so (PaUtil_EndBufferProcessing+284) (BuildId: 8b1f19c01e1ec1e45d1a31ebdeaa61b42bc28018)

[fixxiefixx]

I tested today an effect chain with an echo effect in the 2.5 branch and AddressSanitizer enabled and got this error in the console while loading the first song into deck 1:

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/fixx/Programmierprojekte/mixxx-src/src/effects/backends/
builtin/echoeffect.cpp:187 in EchoEffect::processChannel(EchoGroupState*, float const*, float*, mixxx::EngineParameters const&, EffectEnableState, GroupFeatureState const&)
Shadow bytes around the buggy address:
  0x7bb4bfde3d80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bb4bfde3e00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bb4bfde3e80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bb4bfde3f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x7bb4bfde3f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x7bb4bfde4000:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bb4bfde4080: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bb4bfde4100: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bb4bfde4180: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bb4bfde4200: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x7bb4bfde4280: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==27856==ABORTING