Method _streamHandler

examples/WebCamServer/ESP32WebCam.cpp:392–485

* The URL handler for streaming repeatedly sends the image data captured by * the sensor as a series of JPEG frames (Motion-JPEG) of multipart content. * @param req The httpd_req_t structure passed from httpd. * @return ESP_OK Image data has sent * @return ESP_FAIL */

 * @return ESP_FAIL
 */
esp_err_t ESP32WebCam::_streamHandler(httpd_req_t* req) {
  static const char bcharsnospace[] = "'()+,-./0123456789:=?abcdefghijklmnopqrstuvwxyz_ABCDEFGHIJKLMNOPQRSTUVWXYZ";
  char  boundary[33];
  char  mime[sizeof(_CONTENT_TYPE) + sizeof(boundary)];
  char  contentBoundary[sizeof(boundary) + 6];

  // Assemble a boundary string from pseudo-random numbers.
  srand(esp_timer_get_time());
  uint8_t c = 0;
  while (c < sizeof(boundary) - 1)
    boundary[c++] = bcharsnospace[(int)_random(sizeof(bcharsnospace) - 1)];
  boundary[c] = '\0';
  sprintf(mime, _CONTENT_TYPE, (const char*)boundary);
  sprintf(contentBoundary, _CONTENT_BOUNDARY, (const char*)boundary);

  // Send headers
  // HTTP/1.1 200
  // Content-Type: multipart/x-mixed-replace;boundary={contentBoundary}
  // Access-Control-Allow-Origin: *
  // X-Framerate: 60
  httpd_resp_set_type(req, mime);
  httpd_resp_set_hdr(req, ESP32WebCam::_ACCESS_CONTROL_ALLOW_ORIGIN, "*");
  httpd_resp_set_hdr(req, "X-Framerate", "60");

  // Repeated transmission of captured JPEG frames
  esp_err_t rc = ESP_OK;
  while (rc == ESP_OK) {
    uint8_t*  jpegBuffer;
    size_t    jpegSize;

    // Indicates the output buffer of the image sensor.
    camera_fb_t*  fb = esp_camera_fb_get();

    if (fb) {
      if (fb->format == PIXFORMAT_JPEG) {
        // If the pixel format of the image sensor is JPEG, it can be read
        // directly from the frame buffer.
        jpegBuffer = fb->buf;
        jpegSize = fb->len;
      }
      else {
        // If the scene is not in JPEG format, it will attempt to revert to
        // JPEG, but this does not always work. Since most of the failures are
        // due to lack of memory, you can avoid conversion errors by reducing
        // the JPEG quality of the resulting image.
        bool  jpegcc = frame2jpg(fb, 80, &jpegBuffer, &jpegSize);
        esp_camera_fb_return(fb);
        fb = nullptr;
        if (!jpegcc) {
          _sendResponse(req, 500, "text/plain", "_streamHandler failed to frame2jpg");
          rc = ESP_FAIL;
          break;
        }
      }
    }
    else {
      _sendResponse(req, 500, "text/plain", "_streamHandler failed to esp_camera_fb_get");
      rc = ESP_FAIL;