Crash with jack input and output.external

[Yamakaky]

Describe the bug
When the following output.external restarts after a blank period, I get this crash:

2019/10/16 22:19:08 [clock.wallclock_bjack:2] Source r128(dot)voice failed while streaming: File "outputs/pipe_output.ml", line 123, characters 4-10: Assertion failed!
2019/10/16 22:19:08 [clock.wallclock_bjack:3] Raised at file "outputs/pipe_output.ml", line 123, characters 4-49
2019/10/16 22:19:08 [clock.wallclock_bjack:3] Called from file "tools/start_stop.ml", line 99, characters 6-16
2019/10/16 22:19:08 [clock.wallclock_bjack:3] Called from file "outputs/output.ml", line 164, characters 4-18
2019/10/16 22:19:08 [clock.wallclock_bjack:3] Called from file "clock.ml", line 160, characters 17-25
2019/10/16 22:19:08 [main:3] Shutdown started!

the output, with voice being a pipeline starting with a input.jack:

output.external(
    id = "r128.voice",
    flush = true,
    fallible = true,
    %wav(stereo, samplerate = 48000),
    "/r128.py voice",
    strip_blank(
        id = "r128.voice.strip_blank",
        start_blank = true,
        voice
    )
)

Note that the output was blank thus stopped when the problem occured.

To Reproduce
Will do this weekend if I find the time, as well as expand this issue with more debugging.

Expected behavior
Should not crash

Version details

• OS: alpine latest
• Version 1.4.0 (opam)

[smimram]

Could we also see the log just before the crash please?

[Yamakaky]

Nothing in particular, just my normal logs.

[Yamakaky]

The failed assertion is this one: https://github.com/savonet/liquidsoap/blob/master/src/outputs/pipe_output.ml#L123. It happens when I unmute the input which comes into jack, so it seems to check out with the method name. Is there a way I could debug the two variables to check which one doesn't have the right value?

output_stop was modified recently to add the if condition, maybe the pipe is now not correctly closed? Could you check if the code seems correct?

I'm trying to find a short code which would trigger the problem...

[Yamakaky]

After testing, I made some progress. My pipeline is simplified as such:

in = input.jack()
out = process(in)
output.external(strip_blank(in))
output.external(switch([{bool}, out])

The idea is that the first output is used to monitor the audio level of the input continuously, while the second monitors the audio stream including music and the input (only when broadcasting).
Setup: the input is silent and the second output is active. When sound comes from in, it crashes.

[smimram]

Could you try to simplify it further to a self-contained script without jack or complicated external program?

I have tried the following but cannot reproduce:

b = ref(false)
in = sine()
out = in
add_timeout(1., fun () -> begin b := true; (-1.) end)
output.external(fallible=true, %wav, "cat > /dev/null", in)
output.external(fallible=true, %wav, "cat > /dev/null", switch([({!b}, out)]))

[smimram]

Btw, it would be nice if you could tell which of the two variables is wrong. The easiest is to replace

assert (not (self#is_open) && encoder = None) ;

by

assert (not (self#is_open));
assert (encoder = None) ;

and see which line raises.

[Yamakaky]

1 month later: I did that, apparently encoder = None.

[Yamakaky]

Interesting: if I use the same input two times, I get the crash. Maybe a faulty shutdown condition?

[smimram]

Thanks. I think I begin to understand the issue, but I cannot reproduce so that I cannot fix the bug. Here is my current script:

b = ref(false)
add_timeout(1., fun () -> begin b := not !b; 1. end)

s = sine()

output.external(id="enc1", fallible=true, %wav, "cat > /dev/null", s)
output.external(id="enc2", fallible=true, %wav, "cat > /dev/null", switch(track_sensitive=false, [({!b}, s)]))
out(mksafe(s))

which should be relatively close to yours. Can you simplify your script so that you don't use jack nor an opaque "process" command? Or modify the above script so that it fails?

[mrdevis]

any progress on using input.jack in 2.0??