feat(example): Automatic detection RGB565 endianess in display_camera_video example

espzav · espzav · commit aa973651ebf4 · 2026-04-07T08:17:04.000+02:00
diff --git a/examples/display_camera_video/main/app_video.c b/examples/display_camera_video/main/app_video.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2025-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: CC0-1.0
  */
@@ -14,6 +14,7 @@
 #include <sys/errno.h>
 #include "esp_err.h"
 #include "esp_log.h"
+#include <inttypes.h>
 #include "linux/videodev2.h"
 #include "esp_video_init.h"
 #include "app_video.h"
@@ -31,6 +32,7 @@ typedef struct {
     size_t camera_buf_size;
     uint32_t camera_buf_hes;
     uint32_t camera_buf_ves;
+    uint32_t camera_pixelformat;
     struct v4l2_buffer v4l2_buf;
     uint8_t camera_mem_mode;
     app_video_frame_operation_cb_t user_camera_video_frame_operation_cb;
@@ -41,6 +43,23 @@ typedef struct {
 
 static app_video_t app_camera_video;
 
+uint32_t app_video_get_pixelformat(void)
+{
+    return app_camera_video.camera_pixelformat;
+}
+
+static void log_v4l2_fourcc(uint32_t f, const char *prefix)
+{
+    char s[5] = {
+        (char)(f & 0xff),
+        (char)((f >> 8) & 0xff),
+        (char)((f >> 16) & 0xff),
+        (char)((f >> 24) & 0xff),
+        0
+    };
+    ESP_LOGI(TAG, "%s: %s (0x%08" PRIx32 ")", prefix, s, f);
+}
+
 int app_video_open(char *dev, video_fmt_t init_fmt)
 {
     struct v4l2_format default_format;
@@ -73,11 +92,10 @@ int app_video_open(char *dev, video_fmt_t init_fmt)
     }
 
     ESP_LOGI(TAG, "width=%" PRIu32 " height=%" PRIu32, default_format.fmt.pix.width, default_format.fmt.pix.height);
+    log_v4l2_fourcc(default_format.fmt.pix.pixelformat, "initial pixel format");
 
-    app_camera_video.camera_buf_hes = default_format.fmt.pix.width;
-    app_camera_video.camera_buf_ves = default_format.fmt.pix.height;
-
-    if (default_format.fmt.pix.pixelformat != init_fmt) {
+    if (init_fmt != APP_VIDEO_FMT_DRIVER_DEFAULT &&
+            default_format.fmt.pix.pixelformat != (uint32_t)init_fmt) {
         struct v4l2_format format = {
             .type = type,
             .fmt.pix.width = default_format.fmt.pix.width,
@@ -116,6 +134,18 @@ int app_video_open(char *dev, video_fmt_t init_fmt)
     }
 #endif
 
+    memset(&default_format, 0, sizeof(struct v4l2_format));
+    default_format.type = type;
+    if (ioctl(fd, VIDIOC_G_FMT, &default_format) != 0) {
+        ESP_LOGE(TAG, "failed to get final format");
+        goto exit_0;
+    }
+
+    app_camera_video.camera_buf_hes = default_format.fmt.pix.width;
+    app_camera_video.camera_buf_ves = default_format.fmt.pix.height;
+    app_camera_video.camera_pixelformat = default_format.fmt.pix.pixelformat;
+    log_v4l2_fourcc(app_camera_video.camera_pixelformat, "capture pixel format");
+
     app_camera_video.video_stop_sem = xSemaphoreCreateBinary();
 
     return fd;
diff --git a/examples/display_camera_video/main/app_video.h b/examples/display_camera_video/main/app_video.h
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2025-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -15,10 +15,13 @@ extern "C" {
 #endif
 
 typedef enum {
+    /** Keep pipeline default (e.g. from menuconfig); do not call VIDIOC_S_FMT for pixel format. */
+    APP_VIDEO_FMT_DRIVER_DEFAULT = 0,
     APP_VIDEO_FMT_RAW8 = V4L2_PIX_FMT_SBGGR8,
     APP_VIDEO_FMT_RAW10 = V4L2_PIX_FMT_SBGGR10,
     APP_VIDEO_FMT_GREY = V4L2_PIX_FMT_GREY,
     APP_VIDEO_FMT_RGB565 = V4L2_PIX_FMT_RGB565,
+    APP_VIDEO_FMT_RGB565_BE = V4L2_PIX_FMT_RGB565X,
     APP_VIDEO_FMT_RGB888 = V4L2_PIX_FMT_RGB24,
     APP_VIDEO_FMT_YUV422 = V4L2_PIX_FMT_YUV422P,
     APP_VIDEO_FMT_YUV420 = V4L2_PIX_FMT_YUV420,
@@ -36,12 +39,18 @@ typedef void (*app_video_frame_operation_cb_t)(uint8_t *camera_buf, uint8_t came
  * vertical or horizontal mirroring if enabled in the configuration.
  *
  * @param dev The device path of the video capture (e.g., "/dev/video0").
- * @param init_fmt The desired pixel format for the video capture.
+ * @param init_fmt The desired pixel format for the video capture, or APP_VIDEO_FMT_DRIVER_DEFAULT
+ *                 to use the format already configured by the driver (sensor / menuconfig).
  * @return Returns the file descriptor for the opened video device on success;
  *         returns -1 on failure, indicating an error occurred during the operation.
  */
 int app_video_open(char *dev, video_fmt_t init_fmt);
 
+/**
+ * @brief V4L2 pixelformat fourcc after app_video_open() (from VIDIOC_G_FMT).
+ */
+uint32_t app_video_get_pixelformat(void);
+
 /**
  * @brief Set up video capture buffers.
  *
diff --git a/examples/display_camera_video/main/main.c b/examples/display_camera_video/main/main.c
@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2025 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2025-2026 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: CC0-1.0
  */
@@ -43,6 +43,19 @@ static size_t data_cache_line_size = 0;
 static lv_obj_t *camera_canvas = NULL;
 static uint8_t *cam_buff[NUM_BUFS];
 static uint32_t cam_buff_size = 0;
+static lv_color_format_t lvgl_cam_rgb565_fmt;
+
+static lv_color_format_t lvgl_rgb565_fmt_from_v4l2(uint32_t pixelformat)
+{
+    if (pixelformat == V4L2_PIX_FMT_RGB565X) {
+        return LV_COLOR_FORMAT_RGB565_SWAPPED;
+    }
+    if (pixelformat == V4L2_PIX_FMT_RGB565) {
+        return LV_COLOR_FORMAT_RGB565;
+    }
+    ESP_LOGW(TAG, "Unexpected RGB565 pixel format, using LV_COLOR_FORMAT_RGB565");
+    return LV_COLOR_FORMAT_RGB565;
+}
 
 #if SOC_PPA_SUPPORTED
 static void app_ppa_init(void)
@@ -156,7 +169,7 @@ static void camera_video_frame_operation(uint8_t *camera_buf, uint8_t camera_buf
 #endif
 
     bsp_display_lock(0);
-    lv_canvas_set_buffer(camera_canvas, out_buf, out_w, out_h, LV_COLOR_FORMAT_RGB565);
+    lv_canvas_set_buffer(camera_canvas, out_buf, out_w, out_h, lvgl_cam_rgb565_fmt);
     lv_obj_center(camera_canvas);
     lv_obj_invalidate(camera_canvas);
     bsp_display_unlock();
@@ -194,22 +207,23 @@ void app_main(void)
         }
     }
 
+    /* Open video first: pixel format comes from menuconfig / driver (VIDIOC_G_FMT). */
+    int fd = app_video_open(BSP_CAMERA_DEVICE, APP_VIDEO_FMT_DRIVER_DEFAULT);
+    if (fd < 0) {
+        ESP_LOGE(TAG, "Failed to open video device");
+        ESP_LOGW(TAG, "Please, try to select another camera sensor in menuconfig.");
+        return;
+    }
+    lvgl_cam_rgb565_fmt = lvgl_rgb565_fmt_from_v4l2(app_video_get_pixelformat());
+
     /* Create LVGL canvas for camera image */
     bsp_display_lock(0);
     camera_canvas = lv_canvas_create(lv_scr_act());
-    lv_canvas_set_buffer(camera_canvas, cam_buff[0], BSP_LCD_H_RES, BSP_LCD_V_RES, LV_COLOR_FORMAT_RGB565);
+    lv_canvas_set_buffer(camera_canvas, cam_buff[0], BSP_LCD_H_RES, BSP_LCD_V_RES, lvgl_cam_rgb565_fmt);
     assert(camera_canvas);
     lv_obj_center(camera_canvas);
     bsp_display_unlock();
 
-    /* Open video device */
-    int fd = app_video_open(BSP_CAMERA_DEVICE, APP_VIDEO_FMT_RGB565);
-    if (fd < 0) {
-        ESP_LOGE(TAG, "Failed to open video device");
-        ESP_LOGW(TAG, "Please, try to select another camera sensor in menuconfig.");
-        return;
-    }
-
     /* Initialize video capture device */
     ret = app_video_set_bufs(fd, NUM_BUFS, NULL);
     if (ret != ESP_OK) {
