# Segmentation fault caused by running multiple concurrent GStreamer pipelines with PyGObject in Python, likely due to GLib/GStreamer thread-safety or main loop issues under concurrency
**URL:** https://discourse.gstreamer.org/t/segmentation-fault-caused-by-running-multiple-concurrent-gstreamer-pipelines-with-pygobject-in-python-likely-due-to-glib-gstreamer-thread-safety-or-main-loop-issues-under-concurrency/5581
**Category:** Newcomers
**Tags:** python
**Created:** [January 1, 2026, 7:48am UTC](https://discourse.gstreamer.org/t/segmentation-fault-caused-by-running-multiple-concurrent-gstreamer-pipelines-with-pygobject-in-python-likely-due-to-glib-gstreamer-thread-safety-or-main-loop-issues-under-concurrency/5581 "2026-01-01T07:48:21Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@Subash](https://discourse.gstreamer.org/u/Subash)
#### Post date: [January 1, 2026, 7:48am UTC](https://discourse.gstreamer.org/t/segmentation-fault-caused-by-running-multiple-concurrent-gstreamer-pipelines-with-pygobject-in-python-likely-due-to-glib-gstreamer-thread-safety-or-main-loop-issues-under-concurrency/5581/1 "2026-01-01T07:48:21Z")
# SIGSEGV with PyGObject + GStreamer under concurrent pipelines (Python)
## Summary
A segmentation fault (SIGSEGV, exit code 139) occurs when running **multiple concurrent GStreamer pipelines** using **PyGObject** in a Python application.
The crash happens **non-deterministically** after some runtime and always under concurrency (\>2 sessions).
No Python exception is raised; the process terminates inside native code.
* * *
## Environment
- OS: Ubuntu 22.04 (Docker)
- Python: 3.10.12
- GStreamer: 1.20.3
- PyGObject: 3.42.1
- Architecture: x86\_64
* * *
## Application overview
- Receives live **WebM/Opus audio over WebSocket**
- Uses **GStreamer (PyGObject)** to:
- Convert WebM Opus → Ogg Opus or PCM
- Each WebSocket session creates:
- Its own GStreamer pipeline
- Its own `GLib.MainLoop` running in a Python thread
- Output is consumed by Azure Cognitive Services Speech SDK
* * *
## Steps to reproduce
1. Run the app inside an Ubuntu 22.04 Docker container.
2. Start the Python server using PyGObject + GStreamer.
3. Open more than **two concurrent WebSocket connections**.
4. Stream audio continuously.
5. After some time, the process crashes with SIGSEGV.
Reproducibility: **Always under concurrency, but timing varies**.
* * *
## Minimal reproduction code
```python
import threading
import gi
gi.require_version('Gst', '1.0')
from gi.repository import Gst, GLib
Gst.init(None)
class WebmGstreamerConverter:
def __init__ (self,pipeline):
# Create the GStreamer pipeline
self.pipeline = Gst.parse_launch(
pipeline
)
# Get source and sink elements
self.src = self.pipeline.get_by_name("src")
self.sink = self.pipeline.get_by_name("sink")
# Connect appsink signal
self.sink.connect("new-sample", self.on_new_sample)
# Start GLib MainLoop in a separate thread
self.loop = GLib.MainLoop()
self.loop_thread = threading.Thread(target=self.loop.run, daemon=True)
self.loop_thread.start()
self.output = []
# Start pipeline
self.pipeline.set_state(Gst.State.PLAYING)
def on_new_sample(self, sink):
"""Callback when a new Ogg sample is available from appsink."""
sample = sink.emit("pull-sample")
buf = sample.get_buffer()
success, map_info = buf.map(Gst.MapFlags.READ)
if success:
self.output.append(map_info.data)
buf.unmap(map_info)
return Gst.FlowReturn.OK
def feed(self, webm_chunk: bytes):
"""Feed WebM data into the GStreamer pipeline."""
buf = Gst.Buffer.new_allocate(None, len(webm_chunk), None)
buf.fill(0, webm_chunk)
# Set timestamps to avoid pipeline stalling
buf.pts = buf.dts = Gst.util_uint64_scale(len(webm_chunk), Gst.SECOND, 8192)
self.src.emit("push-buffer", buf)
def read_ogg(self) -> bytes:
"""Retrieve accumulated Ogg data."""
data = b"".join(self.output)
self.output.clear()
return data
def close(self):
"""Gracefully stop the pipeline."""
self.src.emit("end-of-stream")
self.pipeline.set_state(Gst.State.NULL)
self.loop.quit()
def get_webm_to_ogg_converter() -> WebmGstreamerConverter :
return WebmGstreamerConverter(
"appsrc name=src is-live=true format=time do-timestamp=true ! "
"matroskademux name=demux ! "
"queue ! opusparse ! muxer. "
"oggmux name=muxer ! appsink name=sink emit-signals=true sync=false")
def get_webm_to_pcm_converter() -> WebmGstreamerConverter :
return WebmGstreamerConverter(
"appsrc name=src is-live=true format=time do-timestamp=true ! "
"matroskademux name=demux ! "
"queue ! opusdec ! audioconvert ! audioresample ! "
"audio/x-raw,format=S16LE,channels=1,rate=16000 ! "
"appsink name=sink emit-signals=true sync=false"
)
```
* * *
## Actual behavior
- Process crashes with:
- No Python traceback
- Crash occurs in native threads (GLib / GStreamer / Azure SDK)
* * *
## Expected behavior
- Safe handling of multiple concurrent pipelines
- No memory corruption or process crash
* * *
## Observations / questions
- Each session runs its own `GLib.MainLoop`
- Crash happens in non-Python threads
- Is it safe to:
- Is a **single global GLib main loop** required?
Any guidance or confirmation of known limitations would be appreciated.
---
### Author:  [@slomo](https://discourse.gstreamer.org/u/slomo)
#### Post date: [January 2, 2026, 1:57pm UTC](https://discourse.gstreamer.org/t/segmentation-fault-caused-by-running-multiple-concurrent-gstreamer-pipelines-with-pygobject-in-python-likely-due-to-glib-gstreamer-thread-safety-or-main-loop-issues-under-concurrency/5581/2 "2026-01-02T13:57:04Z")
Duplicate of [Segmentation Fault (SIGSEGV) in GStreamer / GLib Main Loop with Multiple Concurrent PyGObject Pipelines (#4842) · Issues · GStreamer / gstreamer · GitLab](https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/4842)