Quick Answer: Converting LVDS to HDMI means capturing a panel’s internal parallel stream before it reaches the glass and re-framing it as TMDS. The converter must be told exact timing: active pixels, total pixels, sync widths, pixel clock and colour mapping. Get those right and a 1920×1080 panel at 60 Hz needs a 148.5 MHz pixel clock and about 4.46 Gbps of payload, inside HDMI 1.4 at 10.2 Gbps. Get them wrong and you get a rolling, offset or half-green image. Lane count and bit mapping matter more than the chipset.
LVDS is not a video standard with a resolution attached. It is a differential signalling scheme that serialises 7 parallel bits onto each pair at whatever pixel clock the source generates. A panel datasheet describes the mapping, the pair count and the timing, and every detail has to survive conversion. That is why the same board works on one display and shows nothing on another with identical resolution.
What the LVDS Stream Carries
A single LVDS channel uses three data pairs plus one clock pair. Each data pair carries seven bits per clock cycle, so three pairs deliver 21 bits: six bits per colour plus three control bits for HSYNC, VSYNC and data enable. Dual channel doubles that to six data pairs and 42 bits, which is how 1920×1200 and wider panels keep the pixel clock inside what the glass accepts.
The serialiser and the pairs
Inside the source, a parallel RGB bus at 24 or 30 bits is loaded into a shift register and pushed out sequentially, then deserialised at the panel. A converter must sample that stream with the recovered clock and rebuild the parallel bus. Sample on the wrong edge and every pixel shifts one bit, which reads as banding or a magenta cast.
Single versus dual channel
Dual channel splits the screen into left and right halves, each with its own pair set, locked to a shared clock. A converter set for single channel on a dual channel panel captures only the left half and repeats it, or captures nothing because the clock pair it expects carries no timing.
The Timing Numbers the Board Needs
Four values decide whether the output locks: horizontal total, vertical total, pixel clock and sync polarity. Horizontal total is active width plus both blanking intervals. Multiply horizontal total by vertical total by refresh rate and you have the pixel clock, which is what HDMI inherits.
| Panel timing | Data pairs | Pixel clock | HDMI payload | Fits |
|---|
| 1280×800 at 60 Hz | 3 | 71 MHz | 2.1 Gbps | HDMI 1.4 |
| 1366×768 at 60 Hz | 3 or 4 | 85 MHz | 2.6 Gbps | HDMI 1.4 |
| 1920×1080 at 60 Hz | 6 | 148.5 MHz | 4.46 Gbps | HDMI 1.4 |
| 1920×1200 at 60 Hz | 6 | 154 MHz | 4.62 Gbps | HDMI 1.4 |
| 2560×1440 at 60 Hz | 8 | 241 MHz | 7.2 Gbps | HDMI 2.0 |
The payload column is pixel clock multiplied by 30 bits for RGB888. A 2560×1440 panel needs 18 Gbps capable cable and ports, so check the HDMI cable rating categories before blaming the converter.
Scaling and Colour Depth
If the display cannot accept the panel’s native mode, something has to scale. Fixed-function converters often output a standard 1080p frame and letterbox the rest, which is fine for a menu overlay and wrong for an instrument where one pixel must equal one unit. Line buffers keep latency near a frame; full frame stores add 16 to 33 ms. Colour depth is the other trap: a 6-bit panel driven as 8-bit RGB either truncates, which bands gradients, or dithers, which adds noise.
Frame rate conversion
Panels often run at 50, 75 or 60 Hz rather than a broadcast rate. A converter offering only 60 Hz drops or duplicates frames, and on a machine vision line the duplicated frame is a wrong measurement.
EDID and Hot Plug
HDMI expects a sink to answer hot plug detect and serve an EDID block. A bare LVDS panel has neither, so the converter must synthesise both. If the EDID advertises 1080p but the panel is 1280×800, the source sends a mode the converter must rescale and the picture arrives soft. Program the EDID to the native timing where the board allows it.
Practical Scenarios
- Recycled laptop panel on a media player: match panel timing exactly, then set EDID to the same mode; forcing 1080p gives a stretched, soft image.
- Industrial HMI with a 15 m run: keep the LVDS side under 0.5 m, since it is a board-level interface, and take the distance on HDMI.
- Analog monitor from an LVDS source: use a passive HDMI to VGA converter only when the display accepts the mode, because a passive part has no scaler.
- Recording a legacy panel: an HDMI to composite converter downscales to 480i, so accept the loss and lock the frame rate.
FAQ
Why is my image split with a vertical seam?
The converter is treating a dual channel panel as single channel, or the halves are swapped. Check the pair count and confirm whether the board expects odd pixels on channel A and even on channel B.
Do I need a scaler or just a converter?
If source and panel share a mode, a converter is enough and adds almost no latency. Add a scaler only when the panel cannot accept anything the source offers, and expect a frame or more of delay.
What causes a green or magenta cast?
Bit mapping. The converter is reading the LVDS lanes in the wrong order or assuming 24-bit RGB when the panel is 18-bit. Fix the mapping table in the board settings, not the display colour.
