Versions after 13.0.0 have serious memory leaks

[ncheng89]

When repeatedly creating and closing output containers (to segment a video), the memory usage increases steadily and never goes down, indicating a memory leak.
This behavior is not present in PyAV 13.0.0, but shows up in version 14.0.0 and 15.0.0.

Environment
OS: CentOS
Python: 3.9
PyAV versions tested: 13.0.0 ✅, 14.0.0 ❌, 15.0.0 ❌
FFmpeg bundled with PyAV wheels

Notes
Memory increases per segment.
Even after calling out_container.close() and del out_container, memory is not released.
Behavior introduced starting in version 14.0.0.

Test code

import av
import os
import time
import psutil

SEGMENT_DURATION = 10
OUTPUT_DIR = "segments"
INPUT_URL = "http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4"
os.makedirs(OUTPUT_DIR, exist_ok=True)

in_container = av.open(INPUT_URL)

video_stream = in_container.streams.video[0]
audio_stream = in_container.streams.audio[0] if in_container.streams.audio else None

video_pts = 0
audio_pts = 0
segment_index = 0
out_container = None
out_video_stream = None
out_audio_stream = None
segment_start_time = None
video_time_base = video_stream.time_base
audio_time_base = audio_stream.time_base if audio_stream else None


def start_new_segment():
    global out_container, out_video_stream, out_audio_stream, video_pts, audio_pts
    output_path = os.path.join(OUTPUT_DIR, f"segment{int(time.time())}.mp4")
    out_container = av.open(output_path, mode="w")
    if av.__version__ > "13.0.0":
        out_video_stream = out_container.add_stream_from_template(template=video_stream, rate=video_stream.average_rate)
        out_video_stream.time_base = video_stream.time_base
    else:
        out_video_stream = out_container.add_stream(template=video_stream, rate=video_stream.average_rate)

    if audio_stream:
        if av.__version__ > "13.0.0":
            out_audio_stream = out_container.add_stream_from_template(audio_stream)
            out_audio_stream.time_base = audio_stream.time_base
        else:
            out_audio_stream = out_container.add_stream("aac", rate=audio_stream.rate)
    video_pts = 0
    audio_pts = 0
    rss = psutil.Process(os.getpid()).memory_info().rss / 1024 / 1024
    print(f"Current process memory usage: {rss:.2f}MB, av version:{av.__version__}")


start_new_segment()

for packet in in_container.demux((video_stream, audio_stream) if audio_stream else video_stream):
    if packet.pts is None:
        continue
    if segment_start_time is None and packet.stream.type == 'video':
        segment_start_time = float(packet.pts * packet.time_base)

    if packet.stream.type == 'video':
        current_time = float(packet.pts * packet.time_base)
        if current_time - segment_start_time >= SEGMENT_DURATION:
            if segment_index > 15:
                break
            out_container.close()
            del out_container
            segment_index += 1
            segment_start_time = float(packet.pts * packet.time_base)
            start_new_segment()

    if packet.stream.type == 'video':
        packet.pts = video_pts
        packet.dts = video_pts
        packet.stream = out_video_stream
        out_container.mux(packet)
        video_pts += int(1 / float(video_time_base * video_stream.average_rate))

    elif packet.stream.type == 'audio':
        packet.pts = audio_pts
        packet.dts = audio_pts
        packet.stream = out_audio_stream
        out_container.mux(packet)
        if packet.duration:
            audio_pts += packet.duration
        else:
            audio_pts += int(audio_stream.rate / 100)

if out_container:
    out_container.close()
in_container.close()

output log

(.venv) [root@serverData test_av]# python test.py      
Current process memory usage: 43.12MB, av version:13.0.0
Current process memory usage: 46.61MB, av version:13.0.0
Current process memory usage: 46.62MB, av version:13.0.0
Current process memory usage: 47.26MB, av version:13.0.0
Current process memory usage: 47.26MB, av version:13.0.0
Current process memory usage: 47.27MB, av version:13.0.0
Current process memory usage: 47.27MB, av version:13.0.0
Current process memory usage: 47.27MB, av version:13.0.0
Current process memory usage: 47.29MB, av version:13.0.0
Current process memory usage: 47.29MB, av version:13.0.0
Current process memory usage: 47.29MB, av version:13.0.0
Current process memory usage: 47.29MB, av version:13.0.0
Current process memory usage: 47.29MB, av version:13.0.0
Current process memory usage: 47.30MB, av version:13.0.0
Current process memory usage: 47.30MB, av version:13.0.0
Current process memory usage: 47.37MB, av version:13.0.0
Current process memory usage: 47.38MB, av version:13.0.0
(.venv) [root@serverData test_av]# pip install -U av==14.0.0           
Looking in indexes: http://mirrors.aliyun.com/pypi/simple
Collecting av==14.0.0
  Using cached http://mirrors.aliyun.com/pypi/packages/76/0f/83c2476dadc245b9c76d90ae3828322a8f7eab02830ba57227ff3793cefb/av-14.0.0-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (33.1 MB)
Installing collected packages: av
  Attempting uninstall: av
    Found existing installation: av 13.0.0
    Uninstalling av-13.0.0:
      Successfully uninstalled av-13.0.0
Successfully installed av-14.0.0
WARNING: You are using pip version 22.0.4; however, version 25.2 is available.
You should consider upgrading via the '/tmp/test_av/.venv/bin/python3 -m pip install --upgrade pip' command.
(.venv) [root@serverData test_av]# python test.py            
Current process memory usage: 42.43MB, av version:14.0.0
Current process memory usage: 49.29MB, av version:14.0.0
Current process memory usage: 61.54MB, av version:14.0.0
Current process memory usage: 67.30MB, av version:14.0.0
Current process memory usage: 68.96MB, av version:14.0.0
Current process memory usage: 69.21MB, av version:14.0.0
Current process memory usage: 71.29MB, av version:14.0.0
Current process memory usage: 85.32MB, av version:14.0.0
Current process memory usage: 73.05MB, av version:14.0.0
Current process memory usage: 73.21MB, av version:14.0.0
Current process memory usage: 73.21MB, av version:14.0.0
Current process memory usage: 71.30MB, av version:14.0.0
Current process memory usage: 72.96MB, av version:14.0.0
Current process memory usage: 71.31MB, av version:14.0.0
Current process memory usage: 73.30MB, av version:14.0.0
Current process memory usage: 71.32MB, av version:14.0.0
Current process memory usage: 71.32MB, av version:14.0.0
(.venv) [root@serverData test_av]# pip install -U av==15.0.0  
Looking in indexes: http://mirrors.aliyun.com/pypi/simple
Collecting av==15.0.0
  Using cached http://mirrors.aliyun.com/pypi/packages/b3/46/3c192579f73d00eb4e856b6a25b1b128a20a70fe07a8268b67dc1ad4dc75/av-15.0.0-cp39-cp39-manylinux_2_28_x86_64.whl (39.3 MB)
Installing collected packages: av
  Attempting uninstall: av
    Found existing installation: av 14.0.0
    Uninstalling av-14.0.0:
      Successfully uninstalled av-14.0.0
Successfully installed av-15.0.0
WARNING: You are using pip version 22.0.4; however, version 25.2 is available.
You should consider upgrading via the '/tmp/test_av/.venv/bin/python3 -m pip install --upgrade pip' command.
(.venv) [root@serverData test_av]# python test.py            
Current process memory usage: 43.55MB, av version:15.0.0
Current process memory usage: 50.46MB, av version:15.0.0
Current process memory usage: 60.64MB, av version:15.0.0
Current process memory usage: 67.48MB, av version:15.0.0
Current process memory usage: 72.09MB, av version:15.0.0
Current process memory usage: 74.25MB, av version:15.0.0
Current process memory usage: 84.64MB, av version:15.0.0
Current process memory usage: 84.67MB, av version:15.0.0
Current process memory usage: 86.64MB, av version:15.0.0
Current process memory usage: 81.08MB, av version:15.0.0
Current process memory usage: 91.11MB, av version:15.0.0
Current process memory usage: 95.83MB, av version:15.0.0
Current process memory usage: 95.86MB, av version:15.0.0
Current process memory usage: 97.93MB, av version:15.0.0
Current process memory usage: 98.64MB, av version:15.0.0
Current process memory usage: 102.68MB, av version:15.0.0
Current process memory usage: 104.69MB, av version:15.0.0
(.venv) [root@serverData test_av]#