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Image Artifacts in 12MP Capture with i.MX8MP GStreamer Pipeline

Hello,

I'm developing a Qt application for the i.MX8MP targeting a 12MP image capture device and encountering image artifacts in the captured PNG images.

Hardware/Software Environment:

SoC: NXP i.MX8MP
Camera: 12MP sensor via MIPI CSI-2 (CSI1)
Framework: Qt with GStreamer
Capture resolution: 4048x3040

GStreamer Pipeline:

c

descr = g_strdup_printf("v4l2src name=video_source "
                        "device=/dev/video-isp-csi1 "
                        "io-mode=dmabuf ! "
                        "video/x-raw, width=4048,height=3040 ! tee name=t "
                        "t. ! queue max-size-buffers=1 leaky=downstream ! imxvideoconvert_g2d "
                        "name=g2d rotation=3 ! video/x-raw, width=480, height=800 ! appsink "
                        "name=app_sink_live max-buffers=1 drop=True "
                        "t. ! queue ! appsink name=app_sink_snapshot max-buffers=1 drop=True");

Issue: The captured PNG images frequently contain visual artifacts (see attached image). The artifacts appear as corrupted regions or visual distortions in the final image.

Observations:

MIPI CSI debug logs indicate the CSI signal appears to be stable and correct
The issue occurs intermittently but frequently enough to be problematic
Both the live preview path (with rotation and scaling) and snapshot path are affected

Questions:

Could this be a buffer synchronization issue between the ISP and the downstream elements?
Are there recommended buffer settings or pipeline configurations for high-resolution capture on i.MX8MP?
Could the dmabuf io-mode be causing memory coherency issues?
Are there any known issues with the ISP driver at this resolution?

Any guidance would be greatly appreciated!

Image:

i.MX8ULP

Multimedia

Re: Image Artifacts in 12MP Capture with i.MX8MP GStreamer Pipeline

Hi,
Thank you for taking your time. I could finally solve the problem.
FYI: I am stick to DMA in this case because its 12MP and image buffers are to big for user space manipulations.

No image artifacts are seen anymore After adding clean stop (GST_STATE_NULL) in bool GstVideoPipeline::stop() and after we wait for state change to complete to ensure ISP device is closed:
ret = gst_element_get_state(m_pimpl->pipeline, &state, &pending, GST_CLOCK_TIME_NONE);

now the Gstreamer pipeline stop is as follows:

bool GstVideoPipeline::stop() {
    if (!VideoPipeline::stop()) {
        return false;
    }

    GstStateChangeReturn ret = gst_element_set_state(m_pimpl->pipeline, GST_STATE_NULL);
    if (ret == GST_STATE_CHANGE_FAILURE) {
        qCritical() << "Failed to change pipeline state to NULL";
        return false;
    }

    // Wait for state change to complete to ensure ISP device is closed 
    // this is key to image artifact issue
    GstState state, pending;
    ret = gst_element_get_state(m_pimpl->pipeline, &state, &pending, GST_CLOCK_TIME_NONE);
    if (ret == GST_STATE_CHANGE_FAILURE) {
        qCritical() << "Failed to wait for NULL state";
        return false;
    }

    // Release references to child elements so they can be properly freed
    if (m_pimpl->g2d != nullptr) {
        gst_object_unref(m_pimpl->g2d);
        m_pimpl->g2d = nullptr;
    }
    if (m_pimpl->appSinkLive != nullptr) {
        gst_object_unref(m_pimpl->appSinkLive);
        m_pimpl->appSinkLive = nullptr;
    }
    if (m_pimpl->appSinkSnapshot != nullptr) {
        gst_object_unref(m_pimpl->appSinkSnapshot);
        m_pimpl->appSinkSnapshot = nullptr;
    }

    qDebug() << "Pipeline stopped and all resources freed";
    return true;
}

Re: Image Artifacts in 12MP Capture with i.MX8MP GStreamer Pipeline

Hello.

What sensor model is being used? are you using a custom ISP tuning file (XML)?. There are know issues with debayering and ISP configuration if sensor-specific tuning or profile is not properly adapted (image quality may degrade over time)

>Could this be a buffer synchronization issue between the ISP and the downstream elements?>Are there recommended buffer settings or pipeline configurations for high-resolution capture on i.MX8MP?

In your pipeline, max-size-buffers=1 limits the queue to hold only one buffer, If the downstream element is slow (encoding or saving) the buffer may be dropped Can you try increasing buffer sizes + leaky=no to prevent buffer drops: max-size-buffers=4 leaky=no

Could you also try to use use filesink instead of appsink to debug image output independently of Qt

>Could the dmabuf io-mode be causing memory coherency issues?

Can you test your pipeline using io-mode=mmap and io-mode=auto to discart dmabuf issues

>Are there any known issues with the ISP driver at this resolution?

8MP ISP supports up to 4096x3072, where width must be divisible by 16 and height by 8 due to macroblock alignment for dewarp and ISP processing. Your resolution of 4048x3046 is valid

Regards