Playback inconsistently ending one frame before

[rodrigoberriel]

Preliminary Checks

• This issue is not a duplicate. Before opening a new issue, please search existing issues.
• This issue is not a question, feature request, or anything other than a bug report directly related to this project.

Description

The playback, via python, sometimes ends one frame before the expected. The behavior is not deterministic, but I was able to consistently reproduce it in many PC configurations with several videos recorded from different ZED versions (ZED 1, ZED 2, and ZED 2i).

Steps to Reproduce

To reproduce it, I used the playback snippet provided in the official website, with small changes to print additional info:

# FROM: https://www.stereolabs.com/docs/video/using-video/#video-playback
import sys
import pyzed.sl as sl

# Set SVO path for playback
input_path = sys.argv[1]
init_parameters = sl.InitParameters()
init_parameters.set_from_svo_file(input_path)

# Open the ZED
zed = sl.Camera()
err = zed.open(init_parameters)

svo_image = sl.Mat()
while True:
    if zed.grab() == sl.ERROR_CODE.SUCCESS:
        # Read side by side frames stored in the SVO
        zed.retrieve_image(svo_image, sl.VIEW.SIDE_BY_SIDE)
        # Get frame count
        svo_position = zed.get_svo_position()
    elif zed.grab() == sl.ERROR_CODE.END_OF_SVOFILE_REACHED:
        print("SVO end has been reached.")
        print(f"Current SVO position: {svo_position + 1}")
        print(f"Nb of frames: {zed.get_svo_number_of_frames()}")
        print(f"Nb of frames dropped: {zed.get_frame_dropped_count()}")
        exit()

Expected Result

I would expect the "Current SVO position" to be equal to the "Nb of frames". The number of frames dropped is reported just in case as well.

Actual Result

But if I run it 10 times, they are different (the difference is always equal to one) in a few of them:

for i in {1..10}; do python3 playback.py HD1080_SN23944511_16-20-25.svo; done

SVO end has been reached.
Current SVO position: 182     # <<<<<
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 183
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 182     # <<<<<
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 183
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 182     # <<<<<
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 183
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 183
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 183
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 183
Nb of frames: 183
Nb of frames dropped: 0
SVO end has been reached.
Current SVO position: 182     # <<<<<
Nb of frames: 183
Nb of frames dropped: 0

The video I used above was a recording of a wall :) recorded only to reproduce the bug and share in this issue: HD1080_SN23944511_16-20-25.zip.

ZED Camera model

ZED, ZED2, and ZED 2i

Environment

I tried on several environments, locally and in the cloud.

OS: Ubuntu 20.04 and 22.04
GPU: GTX 1050 Ti, Tesla T4, and Tesla V100.
ZED SDK VERSION: v3.7.6 and v3.8.0
Other info: I tried it in docker containers and directly on the host.

Anything else?

I tried to disable depth at runtime (passing depth_mode=sl.DEPTH_MODE.NONE to sl.InitParameters(...)), which I was expecting to improve the situation, but exactly the opposite happens: the inconsistency becomes far more frequent.

I also tried videos from different ZED versions: ZED, ZED 2, ZED 2i. All of them presented the same issue.

Is this expected?

[AlexanderKhazatsky]

I have ran into this issue as well

[rodrigoberriel]

Update: I sent this issue to support@stereolabs.com and the response was:

We are aware of this bug and will fix it.
If it's a big issue for you, the best would be to use 3.8.2.

In this context, I reproduced the steps provided in the description of this issue using SDK 3.8.1 and 3.8.2 and the problem persists. It happens as frequently as I reported before.

As an additional feedback, I also tried using SDK 4.0.1 (early access) and the issue there is different: the playback consistently ends one frame earlier.

I asked them whether there is anything else to try or if we should wait for a fix. I'll post an update in case they answer to directly to me.

[github-actions]

This issue is stale because it has been open 30 days with no activity. Remove stale label or comment otherwise it will be automatically closed in 5 days

[rodrigoberriel]

Update: On September 22, 2025, I sent another email reporting that the issue was still present in SDK 5.0.6 (the latest release at the time). @Myzhar, who has been very helpful, replied:

I've reported the problem again to the team, they will fix it, and they will verify that it is not affecting SVOv2 too.

I've just tested SDK 5.1, and unfortunately, the issue still persists. I'll share any updates as soon as I have them.

[Myzhar]

Hi @rodrigoberriel
The SDK team is aware of this issue and they will work on it as soon as possible.