Add on_video_send callback to esp_webrtc

components/esp_webrtc/include/esp_webrtc.h

@@ -79,6 +79,17 @@ typedef struct {
     int (*on_channel_open)(esp_peer_data_channel_info_t *ch, void *ctx);   /*!< Callback invoked when a data channel is opened */
     int (*on_data)(esp_peer_data_frame_t *frame, void *ctx);               /*!< Callback invoked when data is received on the channel */
     int (*on_channel_close)(esp_peer_data_channel_info_t *ch, void *ctx);  /*!< Callback invoked when a data channel is closed */
+    /**
+     * @brief  Video frame send callback (for frame modification/SEI injection)
+     * @param[in]  frame  Video frame information before sending
+     * @param[in]  ctx    User context
+     * @return            Modified frame data or NULL to use original
+     * @note              This callback allows intercepting and modifying outgoing video frames
+     *                    Return the original frame->data to pass through unchanged
+     *                    Return modified data (caller must manage memory) to send modified frame
+     *                    Return NULL to drop the frame
+     */
+    uint8_t* (*on_video_send)(esp_peer_video_frame_t* frame, void* ctx);  /*!< Callback invoked when a video frame is sent */
 } esp_webrtc_peer_cfg_t;
 
 /**

components/esp_webrtc/src/esp_webrtc.c

@@ -144,7 +144,25 @@ static void _media_send(void *ctx)
                     .data = video_frame.data,
                     .size = video_frame.size,
                 };
-                esp_peer_send_video(rtc->pc, &video_send_frame);
+                // Call the video send callback if provided (for SEI injection, etc.)
+                bool should_send = true;
+                if (rtc->rtc_cfg.peer_cfg.on_video_send) {
+                    uint8_t *modified_data = rtc->rtc_cfg.peer_cfg.on_video_send(&video_send_frame, rtc->rtc_cfg.peer_cfg.ctx);
+                    if (modified_data == NULL) {
+                        // Callback returned NULL - drop the frame
+                        should_send = false;
+                    } else if (modified_data != video_send_frame.data) {
+                        // Callback returned modified data - create a copy of the frame info
+                        // to avoid modifying the original capture frame
+                        video_send_frame.data = modified_data;
+                        // Size might have changed - callback should update video_send_frame.size if needed
+                    }
+                    // If modified_data == video_send_frame.data, original frame is unchanged
+                }
+
+                if (should_send) {
+                    esp_peer_send_video(rtc->pc, &video_send_frame);
+                }
             }
             esp_capture_release_path_frame(rtc->capture_path, &video_frame);
             rtc->vid_send_pts = video_frame.pts;