DxConvert

DxConvert is an element that converts video frames between different color formats.
DxConvert uses the VideoTransformFactory to automatically select the best available hardware-accelerated backend (RGA on RK3588) or falls back to the libyuv software backend.

Key Features

Color Format Conversion

• Converts video frames between NV12, I420, RGB, and BGR pixel formats.
• Supports all 4×4 format combinations (e.g., NV12→RGB, I420→BGR, RGB→NV12, etc.).

Same-Format Passthrough

• When the input and output formats are identical, the element passes frames through without any modification (in-place).

Automatic Backend Selection

• On RK3588 platforms with RGA hardware: attempts RGA-accelerated conversion first (currently supports NV12→RGB and NV12→BGR).
• Falls back to libyuv software conversion if the hardware backend does not support the source format or format combination.

Hierarchy

GObject
 +----GInitiallyUnowned
       +----GstObject
             +----GstElement
                   +----GstBaseTransform
                         +----GstDxConvert

Pad Templates

Sink (input)

Property	Value
Format	video/x-raw, format=(string){ NV12, I420, RGB, BGR }

Src (output)

Property	Value
Format	video/x-raw, format=(string){ NV12, I420, RGB, BGR }

Properties

DxConvert has no configurable properties. The target format is negotiated automatically through GStreamer caps negotiation.

Usage Example

Convert an NV12 stream to RGB:

gst-launch-1.0 \
  filesrc location=input.mp4 ! decodebin ! \
  video/x-raw,format=NV12 ! \
  dxconvert ! \
  video/x-raw,format=RGB ! \
  autovideosink

Convert I420 to BGR before inference:

gst-launch-1.0 \
  filesrc location=input.mp4 ! decodebin ! \
  video/x-raw,format=I420 ! \
  dxconvert ! \
  video/x-raw,format=BGR ! \
  dxpreprocess preprocess-id=1 ... ! \
  dxinfer ...

Combine with DxScale — convert format and resize in a pipeline:

gst-launch-1.0 \
  filesrc location=input.mp4 ! decodebin ! \
  video/x-raw,format=NV12 ! \
  dxconvert ! \
  video/x-raw,format=RGB ! \
  dxscale width=640 height=480 ! \
  autovideosink

NOTE

• dxconvert does not perform scaling. Input and output resolutions must match.

• For video scaling, use DxScale.
• On RK3588, RGA hardware acceleration is available for NV12→RGB and NV12→BGR conversions. Other combinations use the libyuv software backend.

DxInputSelector Placement

dxconvert must not be placed downstream of DxInputSelector. DxInputSelector merges multiple streams with potentially different color formats into a single output, causing caps to change on every buffer. Since dxconvert is a GstBaseTransform element, it requires stable caps for buffer pool allocation and kernel initialization. Placing it after DxInputSelector will cause repeated caps renegotiation, kernel re-creation, and potential caps/buffer mismatch errors.

Place dxconvert before DxInputSelector (per-stream) or after DxOutputSelector (per-stream).

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