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rphii
Associate III
Jul 3, 2026 9:53 AM UTC
Solved

STM32N6 Unable to run VENC parallel to DCMIPP

Hi all,

 

I merged the VENC_JPEG_Encoding example with a DCMIPP app. Both parts work on their own, but the JPEG encoding breaks (error -9 = JPEGENC_HW_BUS_ERROR) as soon as I turn on the DCMIPP capture. The JPEG input/output buffer is completely unrelated to the DCMIPP buffer. It’s just that as soon as I start the DCMIPP in CONTINUOUS mode, the JPEG encoder breaks… Very strange.

Did anyone else experience this problem? What could cause this? How would I fix this?

 

Best regards, rphii

rphiiBest answer
Associate III
Jul 9, 2026 4:27 PM UTC

Very long story very short, it works with this setup:

  • PIPE1 → buffer → VENC JPEG
  • pPipeConfig.FrameRate = DCMIPP_FRAME_RATE_1_OVER_2;

I was a fool for thinking this would work:

  • PIPE1 → buffer a/b → DMA2D → jpeg input → VENC JPEG
  • pPipeConfig.FrameRate = DCMIPP_FRAME_RATE_ALL;

By the way, you can still run PIPE2 capturing every frame. And since it shares its demosaic unit somewhat with PIPE1, this is still perfectly doable:


  HAL_DCMIPP_CSI_PIPE_DoubleBufferStart(&hdcmipp, DCMIPP_PIPE2, DCMIPP_VIRTUAL_CHANNEL0, buffer_a, buffer_b, DCMIPP_MODE_CONTINUOUS);
  HAL_DCMIPP_CSI_PIPE_Start(&hdcmipp, DCMIPP_PIPE1, DCMIPP_VIRTUAL_CHANNEL0, jpeg_input, DCMIPP_MODE_CONTINUOUS);

 

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2 replies

rphiiAuthor
Associate III
Jul 8, 2026 3:43 PM UTC

Update: (no solution yet)

Looking at the example here https://github.com/STMicroelectronics/STM32CubeN6/tree/main/Projects/STM32N6570-DK/Applications/VENC/VENC_SDCard uses the H264 encoder parallel to the CSI, they use the `BSP_CAMERA_DoubleBufferStart` and `BSP_CAMERA_FrameEventCallback`. I am assuming that they are functionally the same as `HAL_DCMIPP_PIPE_FrameEventCallback` and `HAL_DCMIPP_CSI_PIPE_DoubleBufferStart` respectively. My code now has basically the same “data flow”, without using the BSP but rather the HAL things.

As I see it, there is one example where they show how to use the VENC to encode JPEG static images (not parallel to the DCMIPP CSI), which is the VENC_JPEG_Encoding as stated above… I can’t find another example, right?

One thing that I saw - which I don’t know if it makes a difference or not - is that they enabled the region which they want to encode as noncacheable via. the MPU. I now added this to my code as well, applying the attributes to my three buffers (jpeg output, dcmipp buffer 1 + 2), to no avail.

I am getting images, the DCMIPP CSI interface is working. But I still can’t run the JPEG VENC to encode images parallel to it, still getting the HW bus error.

rphiiAuthorBest answer
Associate III
Jul 9, 2026 4:27 PM UTC

Very long story very short, it works with this setup:

  • PIPE1 → buffer → VENC JPEG
  • pPipeConfig.FrameRate = DCMIPP_FRAME_RATE_1_OVER_2;

I was a fool for thinking this would work:

  • PIPE1 → buffer a/b → DMA2D → jpeg input → VENC JPEG
  • pPipeConfig.FrameRate = DCMIPP_FRAME_RATE_ALL;

By the way, you can still run PIPE2 capturing every frame. And since it shares its demosaic unit somewhat with PIPE1, this is still perfectly doable:


  HAL_DCMIPP_CSI_PIPE_DoubleBufferStart(&hdcmipp, DCMIPP_PIPE2, DCMIPP_VIRTUAL_CHANNEL0, buffer_a, buffer_b, DCMIPP_MODE_CONTINUOUS);
  HAL_DCMIPP_CSI_PIPE_Start(&hdcmipp, DCMIPP_PIPE1, DCMIPP_VIRTUAL_CHANNEL0, jpeg_input, DCMIPP_MODE_CONTINUOUS);

 

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