Vspipe Hangs: Vs-jetpack And Current HEAD Issues

by SLV Team 49 views
vspipe Gets Stuck During Shutdown: A Deep Dive into vs-jetpack and Current HEAD

Hey everyone! Ever run into a situation where your vspipe script runs perfectly fine, spits out all the right info, but then just… hangs? Like, 100% CPU usage, no end in sight? Yeah, it's a frustrating experience. I recently ran into this issue myself, and after some digging, I've got some insights to share. This is a common issue when using vspipe with the current HEAD of vs-jetpack and a specific set of circumstances.

The Setup: Python, VapourSynth, and vs-jetpack

Let's get the technical stuff out of the way first. I was working with:

  • Python 3.13: The programming language I was using.
  • VapourSynth 15a32152 (current HEAD): The video processing framework I was using.
  • vs-jetpack 38c167be39b5cf21eb3e99b1315bf30218159f2f (current HEAD): A set of VapourSynth plugins used for video processing.

My VapourSynth script was designed to deinterlace some video footage. Here's a simplified version of the script I was using:

import vapoursynth as vs
import vsdeinterlace as vsdeint

src = vs.core.d2v.Source('/path/to/VTS_01_1.d2v')

deinterlaced = (vsdeint.QTempGaussMC(src)
    .prefilter()
    .analyze()
    .denoise()
    .basic()
    .source_match()
    .lossless()
    .sharpen()
    .back_blend()
    .sharpen_limit()
    .final()
    .motion_blur()
    .deinterlace()
)
deinterlaced.set_output()

This script reads a video, processes it with a series of filters (including the crucial QTempGaussMC deinterlacer from vsdeinterlace), and then outputs the processed video. Everything seemed fine until the script was finished processing. Then, it would hang.

The Problem: vspipe's Shutdown Hang

The script worked. It correctly loaded the video, applied the filters, and showed the output information, including the video's dimensions, frame rate, and format. But when it was time to exit, vspipe would get stuck. It would consume 100% CPU, and the only way to get it to stop was to kill the process with a signal.

Using a tool like pstack (which shows the stack trace of a running process) revealed where the hang was happening. The stack trace pointed to a problem within the VapourSynth and potentially the vs-jetpack libraries. This strongly suggested that the issue was happening during the shutdown sequence of vspipe, specifically when it was trying to clean up resources after processing the video.

#0  0x00007f6e67a83058 in <unknown>() in /usr/lib/libpython3.13.so.1.0
#1  0x00007f6e66fca48e in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#2  0x00007f6e66f90abb in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#3  0x00007f6e679620cb in _PyObject_MakeTpCall!()+698 in /usr/lib/libpython3.13.so.1.0
#4  0x00007f6e679e4836 in PyObject_VectorcallMethod!()+261 in /usr/lib/libpython3.13.so.1.0
#5  0x00007f6e66f75551 in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#6  0x00007f6e66fc59a5 in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#7  0x00007f6e67a0c94f in <unknown>() in /usr/lib/libpython3.13.so.1.0
#8  0x00007f6e679c9564 in <unknown>() in /usr/lib/libpython3.13.so.1.0
#9  0x00007f6e67a6bead in <unknown>() in /usr/lib/libpython3.13.so.1.0
#10 0x00007f6e67977635 in _PyEval_EvalFrameDefault!()+19860 in /usr/lib/libpython3.13.so.1.0
#11 0x00007f6e679d1938 in <unknown>() in /usr/lib/libpython3.13.so.1.0
#12 0x00007f6e67a640da in <unknown>() in /usr/lib/libpython3.13.so.1.0
#13 0x00007f6e66f273f3 in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#14 0x00007f6e66f29402 in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#15 0x00007f6e679e47ca in PyObject_VectorcallMethod!()+153 in /usr/lib/libpython3.13.so.1.0
#16 0x00007f6e66f9e355 in <unknown>() in /usr/lib/python3.13/site-packages/vapoursynth.so
#17 0x00007f6e66fa6bc8 in vpy4_freeScript!()+743 in /usr/lib/python3.13/site-packages/vapoursynth.so
#18 0x00007f6e68547a63 in <unknown>() in /usr/lib/libvapoursynth-script.so.0
#19 0x0000555d978c44d1 in <unknown>() in /usr/bin/vspipe
#20 0x00007f6e67e27675 in <unknown>() in /usr/lib/libc.so.6
#21 0x00007f6e67e27729 in __libc_start_main!()+136 in /usr/lib/libc.so.6
#22 0x0000555d978c5a05 in <unknown>() in /usr/bin/vspipe

The Culprit: A vs-jetpack Regression

To find the cause, I started using a technique called bisecting. It's like a binary search for bugs. I tested different versions of vs-jetpack until I pinpointed the commit that introduced the issue. Through this process, I discovered that the problem started with a specific commit in vs-jetpack.

The culprit commit was 99f573685b44eb6bba064e5853347b2d92d7cc59. Using an older version of vs-jetpack, specifically 0.8.5, resolved the issue. This indicated that there was a regression in the current HEAD of the library.

Diving Deeper: Deinterlacing and Source Types

Further investigation revealed some interesting details. While my initial script used core.d2v.Source to load the video (a method for loading DVD files), the issue wasn't directly related to that. The same hang occurred when using core.ffms2.Source to load an MKV file (a common container format) remuxed from a Blu-Ray.

Furthermore, the QTempGaussMC filter was erroring out in this scenario. It complained that the source wasn't interlaced, even though the source material was interlaced. This is a crucial clue.

Possible Causes and Workarounds

So, what's going on here? While I don't have all the answers, here's what I think might be happening, along with some potential workarounds:

  • Interlacing Detection Issues: There might be a bug in how vs-jetpack (or its dependencies) determines if a source is interlaced. If it incorrectly identifies an interlaced source as progressive, QTempGaussMC might fail, leading to an issue during the shutdown.
  • Resource Handling: The infinite loop might be caused by an issue in how vs-jetpack handles resources (memory, threads, etc.) during shutdown when a filter like QTempGaussMC encounters an unexpected state. This could lead to a deadlock or other issues that prevent the script from exiting.
  • Plugin Interactions: There could be an interaction between the vsdeinterlace plugin and other parts of the processing pipeline, particularly when dealing with the source's characteristics.

Workarounds and Solutions

  1. Use an older version of vs-jetpack: As I've already mentioned, reverting to vs-jetpack version 0.8.5 seems to solve the problem. This is a straightforward fix if you need a working solution right away. You can specify the older version when installing or updating the package.
  2. Report the bug: The best thing to do is to report the issue to the vs-jetpack developers. Provide them with the script, the versions of all relevant libraries (VapourSynth, vsdeinterlace, etc.), and the exact steps to reproduce the problem. This will help them fix the underlying issue.
  3. Experiment with alternative deinterlacing methods: If you can't downgrade vs-jetpack or need a temporary solution, you could try using different deinterlacing methods within your script. VapourSynth has a variety of deinterlacing filters available, so you can experiment to find one that works correctly with your source and the current version of vs-jetpack.
  4. Check Source Properties: Ensure that your source video's interlacing properties are correctly identified and passed to the deinterlacing filter. Sometimes, the source information might be incorrect, leading to processing problems. You can use VapourSynth's built-in functions or external tools to verify the source's interlacing flags.

Conclusion: Troubleshooting and Community

This experience highlights the importance of keeping track of software versions and the iterative nature of debugging. By systematically narrowing down the problem and reporting it, we can help improve open-source software like VapourSynth and its plugins. It also emphasizes the importance of the community, as other users might have encountered similar problems and can provide assistance.

If you're facing similar issues, don't hesitate to: 1. Try the workaround of using an older vs-jetpack version. 2. Report the issue. 3. Consult the VapourSynth community for further assistance!

I hope this helps you guys! Let me know in the comments if you have questions or have also faced a similar issue. Happy encoding!