Table of Contents

Enum DecklinkVideoOutputDownConversionMode

Namespace
VisioForge.Core.Types.Decklink
Assembly
VisioForge.Core.dll

Defines hardware-accelerated downconversion modes for outputting HD content as SD video on compatible Decklink cards.

public enum DecklinkVideoOutputDownConversionMode

Fields

Auto = 0

Automatically selects the most appropriate downconversion mode based on the content.

The hardware will analyze the input aspect ratio and AFD (Active Format Description) data to choose between letterbox and anamorphic modes. This is the recommended setting for mixed content workflows.

Disabled = 1

Disables hardware downconversion, outputting the HD signal without conversion.

Use this when you need pure HD output or when downconversion is handled elsewhere in your signal chain. The SD output will either be blank or show the HD signal (if the connected equipment can handle it).

Letterbox16x9 = 2

Downconverts HD 16:9 content to SD with letterboxing (black bars on top and bottom).

Preserves the entire 16:9 image within the 4:3 SD frame by adding horizontal black bars. This is the standard method for maintaining the original aspect ratio and ensuring all content is visible on 4:3 displays.

Output format: - NTSC: 720x486 with ~360 active lines (63 lines black top/bottom) - PAL: 720x576 with ~432 active lines (72 lines black top/bottom)

Anamorphic = 3

Downconverts HD content to anamorphic SD, squeezing the 16:9 image into the full 4:3 frame.

The 16:9 image is horizontally compressed to fit the full height of the 4:3 frame. This format requires a 16:9-capable display or a 4:3 display with anamorphic stretch capability to view correctly. This is the standard for widescreen SD broadcasts.

Commonly used for: - Widescreen SD broadcast channels - DVD production (anamorphic widescreen) - SD distribution to 16:9 displays

AnamorphicCenterCut = 4

Downconverts using center cut extraction, cropping the sides of the 16:9 image to fill the 4:3 frame.

Extracts the center 4:3 portion of the 16:9 HD image, discarding the left and right edges. This mode fills the entire SD frame but loses approximately 25% of the horizontal image content. Use with caution as important visual information may be cropped.

Best suited for content specifically shot with 4:3 center extraction in mind (4:3 safe area). Note: Hardware support for this mode is limited to specific Decklink models like Multibridge Extreme.

Remarks

Downconversion is a critical feature in broadcast facilities that need to simultaneously deliver content in both HD and SD formats. This hardware-based conversion happens in real-time within the Decklink card, eliminating the need for separate SD renders or external converters.

Common use cases include:

  • Broadcasting HD content to legacy SD infrastructure
  • Simultaneous HD and SD playout for multi-format distribution
  • Monitoring HD content on SD reference monitors
  • Creating SD versions for archive or international distribution

Technical considerations: - Downconversion preserves the original frame rate and field order - Color space conversion from HD (BT.709) to SD (BT.601) is applied automatically - The aspect ratio handling depends on the selected mode - Audio passes through unchanged

Not all Decklink models support hardware downconversion. Check your specific model's capabilities before relying on this feature. Models with downconversion typically include it in their product name (e.g., "Decklink Studio 4K" or models with "Extreme" designation).