`samgeo.SamGeo3Video().save_video()` doesn't save the video to disk

[VaasuDC]

Environment Information

• segment-geospatial version: 0.15.2
• Python version: 3.13.6
• Operating System: Windows 11

Description

.save_video() doesn't save the video. It does render the frames to a temporary folder (they are correct) and also it outputs Video saved as out.mp4 and Saved video to out.mp4. However no files are actually created.

What I Did

>>> from samgeo import SamGeo3Video
>>> sam = SamGeo3Video(checkpoint_path=r'weights\sam3.pt')
>>> sam.set_video('cars.mp4')
>>> sam.generate_masks('car')
>>> sam.show_frame(0, axis='on') # it works as expected
>>> sam.save_video('out.mp4', fps=10, show_ids=False)
Video saved as out.mp4
Saved video to out.mp4

[giswqs]

It works fine on my linux machine. I am not sure if it is an issue specific to Windows.

Try calling the images_to_video function to see if it can generate the video. It uses opencv under the hood.

segment-geospatial/samgeo/common.py

Line 3463 in 482c381

def images_to_video(

[VaasuDevanS]

Thanks @giswqs. After some digging, found the actual issue. When we install opencv via uv (or pip), it doesn't include all the codecs (especially avc1). When installed with pixi it works irrespective of the operating system. I tried it on Windows and Ubuntu (via Windows Subsystem for Linux).

Error message for the below code when installed via uv.

Windows

Failed to load OpenH264 library: openh264-1.8.0-win64.dll
        Please check environment and/or download library: https://github.com/cisco/openh264/releases

[libopenh264 @ 000001d4e975bb80] Incorrect library version loaded
[ERROR:0@0.003] global cap_ffmpeg_impl.hpp:3268 open Could not open codec libopenh264, error: Unspecified error (-22)
[ERROR:0@0.003] global cap_ffmpeg_impl.hpp:3285 open VIDEOIO/FFMPEG: Failed to initialize VideoWriter

Windows Subsystem for Linux

[ERROR:0@0.028] global cap_ffmpeg_impl.hpp:3207 open Could not find encoder for codec_id=27, error: Encoder not found
[ERROR:0@0.029] global cap_ffmpeg_impl.hpp:3285 open VIDEOIO/FFMPEG: Failed to initialize VideoWriter

Code to reproduce:

uv: uvx --with "opencv-python==4.12.0.88" python@3.13.11
pixi: pixi exec --spec "python=3.13.11" --spec "opencv==4.12.0" python

import cv2
fourcc = cv2.VideoWriter_fourcc(*"avc1")
video_writer = cv2.VideoWriter("movie.mp4", fourcc, 5, (5,5))

After changing the codec from avc1 to mp4v, the above test code works.

Reference:

• https://stackoverflow.com/a/59686502
• https://swiftlane.com/blog/generating-mp4s-using-opencv-python-with-the-avc1-codec/