cuvid_264 decode conflict with other process

[namogg]

Overview

Thread A running hardware decoder with:
codec = av.codec.CodecContext.create("h264_cuvid", 'r')
Child Process B run cuda.init():

import pycuda.driver as cuda
cuda.init()
cuda_context_0 = cuda.Device(0).make_context()

My code was working fine with h264 but h264_cuvid cause conflict.

Expected behavior

Both process and thread doesnt confict

Actual behavior

Both the thread and the process is corrupted.
Decode thread error:
[Pack decode ] An exception occurred: [Errno 542398533] Generic error in an external library
The other process got error:
pycuda._driver.LogicError: cuInit failed: initialization error

Reproduction

import threading
import multiprocessing
import pycuda.driver as cuda
import av
import numpy as np
import time
import random

def cuda_task():
    try:
        cuda.init()
        print("CUDA initialized in process")
        # Keep the process running
        while True:
            time.sleep(1)
    except Exception as e:
        print(f"[Process] CUDA init error: {e}")

def generate_random_h264_packet():
    # Generate random bytes to simulate an H.264 packet
    packet_size = random.randint(100, 1000)  # Packet size between 100 and 1000 bytes
    return bytearray(random.getrandbits(8) for _ in range(packet_size))

def decode_task():
    try:
        codec = av.codec.CodecContext.create("h264_cuvid", 'r')
        print("Decoder initialized")
        
        while True:
            print("Decoding")
            # Generate random H.264 packet
            packet_data = generate_random_h264_packet()
            packet = av.packet.Packet(packet_data)

            # Decode the packet
            frames = codec.decode(packet)

            
            
            time.sleep(1)  # Simulate some processing delay
    except Exception as e:
        print(f"[Thread] Decoding error: {e}")

if __name__ == "__main__":
    # Using threading for decoding task
    thread = threading.Thread(target=decode_task, daemon=True)
    thread.start()

    # Using multiprocessing for CUDA task
    process = multiprocessing.Process(target=cuda_task)
    process.start()

    # Keep the main process running
    try:
        while True:
            time.sleep(1)
    except KeyboardInterrupt:
        print("Main process interrupted")
        process.terminate()
        process.join()

Investigation

Starting the cuda.init() process first adn keep running doesnt cause error for both side.
Running both in process doesnt cause error

Versions

• OS: Linux
• PyAV runtime:

ai_dev@aidev:~$ python3 -m av --version
PyAV v12.3.0
library configuration: --prefix=/usr --extra-version=0ubuntu0.22.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libdav1d --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librabbitmq --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opencl --enable-opengl --enable-sdl2 --enable-pocketsphinx --enable-librsvg --enable-libmfx --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
library license: GPL version 2 or later
libavcodec     58.134.100
libavdevice    58. 13.100
libavfilter     7.110.100
libavformat    58. 76.100
libavutil      56. 70.100
libswresample   3.  9.100
libswscale      5.  9.100

Research

I have done the following:

• Checked the PyAV documentation
• Searched on Google
• Searched on Stack Overflow
• Looked through old GitHub issues

[namogg]

Changing process from fork to spawn does fix the problem