manmohan_sindhu - 2022-02-08T10:29:43+00:00
Question: Why do I see a green screen when executing a model that contains
Why do I see a green screen when executing a model that contains the Chroma Resampling block from the Video and Image Processing Blockset 1.0 (R14+)? I am using both a camera and the Texas Instruments DM642 Evaluation Module (EVM) in conjunction with my Simulink model. The model contains a Color Space Conversion block, the 'Conversion' parameter of which is set to "R'G'B' to Y'CrCb". The appropriate outputs are fed into a Chroma Resampling block. When the 'Resampling' parameter of the Chroma Resampling block is set to either "4:2:2 to 4:2:0 (MPEG 1)" or "4:2:2 to 4:2:0 (MPEG 2)", then the display connected to my DM642 EVM flashes a green screen.
Expert Answer
Neeta Dsouza answered .
2025-11-20
When the Texas Instruments DM642 Evaluation Module (EVM) exceeds its processor limits, then the video monitor connected to the board displays one of the following symptoms:
- a green screen
- a flashing green screen
- a "frozen" screen (i.e., the video output is not updated)
Using the Chroma Resampling block in a Simulink model can result in this issue.
Note that the DM642 EVM Video ADC and DAC blocks from the Embedded Target for Texas Instruments C6000 DSP library were implemented in such a way that the video signals are transposed. In general, this implementation results in better Simulink performance since the DM642 EVM returns data that is row-major, while Simulink handles column-major data. However, correct use of the Chroma Resampling block involves transposing its inputs and outputs as demonstrated in the attached model named wChromaBlock.mdl. The transpose operations are computationally expensive, and they can easily exceed the processing limits of the DM642 EVM.
To work around this issue, use Selector blocks in lieu of the Chroma Resampling and Transpose blocks. Selector blocks are not as computationally expensive and will improve your system's performance. Such a configuration is demonstrated in the attached model named wSelectorBlock.mdl.
For more information about the Selector block, refer to the documentation accessed by issuing the following command at the MATLAB prompt:
doc selector
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