Color Fidelity Test for Streambox Chroma

Native RGB, XYZ Color and YCrCb 4:2:2 for SDR or HDR

The Streambox Chroma rackmount half-duplex Encoder/Decoder with ACT-L5 codec is well suited for post-production editing and color correction workflows in SDR or HDR. The ACT-L5 codec supports Native RGB and XYZ color space, 10 and 12-bit color depth, and the 4:2:2 and 4:4:4 color profiles. The Streambox Chroma rackmount has been tested for color stability and fidelity and has met SMPTE 372 standard including HDR modes.

Native RGB vs DCI/ICT RGB Test

A color-bar software generator (Blackmagic 4K monitor, SDI out) was connected to a Streambox Chroma Encoder (with Blackmagic 12G Pro, SDI-in) which was connected to a Streambox Chroma Decoder via an IP network hub. The decoder output was to a Blackmagic 4K monitor. On the decoder, we read the SDI value averages before data is passed through the SDI out (after all conversions are complete). Findings:

Native RGB encoding does not perform any color transform and encodes RGB values natively. RGB ICT mode performs RGB transform to/from DCI ICT (compatible with DCI ICT, ISO/IEC 15444-1). Both modes are supported via Streambox Croma UI. Streambox Chroma supports both full and legal ranges.

The following tests were performed in Full range mode:

• Native RGB has less errors than ICT (+1 in last 12-bit digit)
• Clipping for reserved SMPTE 372, 12-bit SDI values:
• Software generated values 0-15 are clipped to 16 by hardware (base)
• Software generated values 4080 to 4096 are mapped to 4079 by hardware (ceiling)

The 10 Bit 4:2:2 Chromatic Test for Rec.709/Rec.2020 (HDR)

A Streambox Chroma Encoder with Decklink 4K Pro was connected through a network hub to an identical Streambox Chroma Decoder. Source format: 1080p24. The encoder was set to Full 2K resolution, 10-bit color depth, 4:2:2 color profile, and Rec 709 color space. The decoder was in test mode. The table below shows that the color values were identical between the source and the decoder out.

The values were stable with no vibration. Since no color space conversion is performed in 4:2:2 mode, the same result applies to Rec.2020 signal fidelity.

Summary

The Streambox Chroma rackmount Encoder/Decoder with ACT-L5 compression and support for Native RGB 4:4:4 and YCrCb 4:2:2 delivers color coding consistent with SMPTE 372 standards. Furthermore, these tests demonstrate that the measured colors before and after chromatic conversions were identical, making the Streambox Chroma ideal for color correction workflows including support Rec.709, DCI P3, Rec.2020, HDR10 PQ/HLG and Dolby Vision.