| .. SPDX-License-Identifier: GPL-2.0 |
| |
| .. include:: <isonum.txt> |
| |
| NPCM video driver |
| ================= |
| |
| This driver is used to control the Video Capture/Differentiation (VCD) engine |
| and Encoding Compression Engine (ECE) present on Nuvoton NPCM SoCs. The VCD can |
| capture a frame from digital video input and compare two frames in memory, and |
| the ECE can compress the frame data into HEXTILE format. |
| |
| Driver-specific Controls |
| ------------------------ |
| |
| V4L2_CID_NPCM_CAPTURE_MODE |
| ~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| The VCD engine supports two modes: |
| |
| - COMPLETE mode: |
| |
| Capture the next complete frame into memory. |
| |
| - DIFF mode: |
| |
| Compare the incoming frame with the frame stored in memory, and updates the |
| differentiated frame in memory. |
| |
| Application can use ``V4L2_CID_NPCM_CAPTURE_MODE`` control to set the VCD mode |
| with different control values (enum v4l2_npcm_capture_mode): |
| |
| - ``V4L2_NPCM_CAPTURE_MODE_COMPLETE``: will set VCD to COMPLETE mode. |
| - ``V4L2_NPCM_CAPTURE_MODE_DIFF``: will set VCD to DIFF mode. |
| |
| V4L2_CID_NPCM_RECT_COUNT |
| ~~~~~~~~~~~~~~~~~~~~~~~~ |
| |
| If using V4L2_PIX_FMT_HEXTILE format, VCD will capture frame data and then ECE |
| will compress the data into HEXTILE rectangles and store them in V4L2 video |
| buffer with the layout defined in Remote Framebuffer Protocol: |
| :: |
| |
| (RFC 6143, https://www.rfc-editor.org/rfc/rfc6143.html#section-7.6.1) |
| |
| +--------------+--------------+-------------------+ |
| | No. of bytes | Type [Value] | Description | |
| +--------------+--------------+-------------------+ |
| | 2 | U16 | x-position | |
| | 2 | U16 | y-position | |
| | 2 | U16 | width | |
| | 2 | U16 | height | |
| | 4 | S32 | encoding-type (5) | |
| +--------------+--------------+-------------------+ |
| | HEXTILE rectangle data | |
| +-------------------------------------------------+ |
| |
| Application can get the video buffer through VIDIOC_DQBUF, and followed by |
| calling ``V4L2_CID_NPCM_RECT_COUNT`` control to get the number of HEXTILE |
| rectangles in this buffer. |
| |
| References |
| ---------- |
| include/uapi/linux/npcm-video.h |
| |
| **Copyright** |copy| 2022 Nuvoton Technologies |
