embassy-rs/embassy · error

YCbCr pixel format not supported for background buffer

Error message

YCbCr pixel format not supported for background buffer

What it means

When converting a PixelFormat for the DMA2D background layer (BGPFCCR), the YCbCr formats are only valid as foreground/chroma input, not for the background buffer. On dma2d_v2 hardware the driver panics rather than writing an invalid CM value.

Solutions

1. Use an RGB/ARGB/L4/A8/A4/AL44/AL88 pixel format for the background layer.
2. Convert YCbCr frames to RGB via the DMA2D foreground chroma path before blitting.
3. Pass the YCbCr format only to the foreground layer where it is accepted.

Example fix

// before
let mut bg = BgLayer::new(&mut dma2d, buf, layout, PixelFormat::YCbCr420);
// after
let mut bg = BgLayer::new(&mut dma2d, buf, layout, PixelFormat::Rgb565);

fn assert_bg_format(f: PixelFormat) {
    assert!(!matches!(f, PixelFormat::YCbCr420 | PixelFormat::YCbCr422),
        "YCbCr not valid for DMA2D background buffer");
}

fn is_bg_pixel_format(f: PixelFormat) -> bool { !matches!(f, PixelFormat::YCbCr420 | PixelFormat::YCbCr422) }

When it happens

Trigger: Creating/configuring a DMA2D background layer with PixelFormat::YCbCr420/YCbCr422 (any non-RGB/alpha variant rejected here) on a dma2d_v2 part.

Common situations: Video pipelines that decode YCbCr and set it as the background framebuffer; copying foreground-layer setup code to the background layer.

Related errors

• Selected output pixel format not supported
• Flexable pixels are not yet implemented
• Can only take the executor once
• Invalid FilterConfig (TooManyFilters)! A FilterConfig must…
• Invalid FilterConfig (EmptyFilterConfig)! A FilterConfig…

AI-assisted analysis of embassy-rs/embassy@463a07b963 (2026-09-10). Data as JSON: /api/errors/62e7c9bb0e35ed21. Report an issue: GitHub.

Appendix: source

Thrown at embassy-stm32/src/dma2d/mod.rs:213

    }
}

impl Into<vals::BgpfccrCm> for PixelFormat {
    fn into(self) -> vals::BgpfccrCm {
        match self {
            PixelFormat::Argb8888 => vals::BgpfccrCm::Argb8888,
            PixelFormat::Rgb888 => vals::BgpfccrCm::Rgb888,
            PixelFormat::Rgb565 => vals::BgpfccrCm::Rgb565,
            PixelFormat::Argb1555 => vals::BgpfccrCm::Argb1555,
            PixelFormat::Argb4444 => vals::BgpfccrCm::Argb4444,
            PixelFormat::L8 => vals::BgpfccrCm::L8,
            PixelFormat::AL44 => vals::BgpfccrCm::Al44,
            PixelFormat::AL88 => vals::BgpfccrCm::Al88,
            PixelFormat::L4 => vals::BgpfccrCm::L4,
            PixelFormat::A8 => vals::BgpfccrCm::A8,
            PixelFormat::A4 => vals::BgpfccrCm::A4,
            #[cfg(dma2d_v2)]
            _ => panic!("YCbCr pixel format not supported for background buffer"),
        }
    }
}

impl Into<vals::OpfccrCm> for PixelFormat {
    fn into(self) -> vals::OpfccrCm {
        match self {
            PixelFormat::Argb8888 => vals::OpfccrCm::Argb8888,
            PixelFormat::Rgb888 => vals::OpfccrCm::Rgb888,
            PixelFormat::Rgb565 => vals::OpfccrCm::Rgb565,
            PixelFormat::Argb1555 => vals::OpfccrCm::Argb1555,
            PixelFormat::Argb4444 => vals::OpfccrCm::Argb4444,
            _ => panic!("Selected output pixel format not supported"),
        }
    }
}

/// Input buffer alpha Mode

View on GitHub (pinned to 463a07b963)