jpeg encoding on the fly for mjpeg stream

Author: eloquentarduino

examples/Encode_Frame_on_the_Fly/Encode_Frame_on_the_Fly.ino

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+/**
+ * Alter camera pixels before sending them via MJPEG stream
+ * (requires enough RAM to run)
+ * (expect 0.5 - 2 FPS)
+ *
+ * BE SURE TO SET "TOOLS > CORE DEBUG LEVEL = INFO"
+ * to turn on debug messages
+ */
+#define WIFI_SSID "SSID"
+#define WIFI_PASS "PASSWORD"
+#define HOSTNAME  "esp32cam"
+
+#include <eloquent_esp32cam.h>
+#include <eloquent_esp32cam/viz/mjpeg.h>
+
+using namespace eloq;
+using namespace eloq::viz;
+
+uint16_t jpeg_length = 0;
+size_t tick = 0;
+
+
+// prototype of the function that will
+// re-encode the frame on-the-fly
+void reencode_frame(WiFiClient *client, camera_fb_t* frame);
+
+// prototype of the functon that will
+// put JPEG-encoded data back into the frame
+size_t buffer_jpeg(void * arg, size_t index, const void* data, size_t len);
+
+
+/**
+ *
+ */
+void setup() {
+    delay(3000);
+    Serial.begin(115200);
+    Serial.println("__RE-ENCODE MJPEG STREAM__");
+
+    // camera settings
+    // replace with your own model!
+    camera.pinout.aithinker();
+    camera.brownout.disable();
+    // higher resolution cannot be handled
+    camera.resolution.qvga();
+    camera.quality.best();
+
+    // since we want to access the raw pixels
+    // capture in RGB565 format
+    // keep in mind that you need a lot of RAM to store
+    // all this data at high resolutions
+    // (e.g. QVGA = 320 x 240 x 2 = 1536 kB)
+    camera.pixformat.rgb565();
+
+    // MJPEG settings
+    mjpeg.onFrame(&reencode_frame);
+
+    // init camera
+    while (!camera.begin().isOk())
+        Serial.println(camera.exception.toString());
+
+    // connect to WiFi
+    while (!wifi.connect().isOk())
+        Serial.println(wifi.exception.toString());
+
+    // start mjpeg http server
+    while (!mjpeg.begin().isOk())
+        Serial.println(mjpeg.exception.toString());
+
+    // assert camera can capture frames
+    while (!camera.capture().isOk())
+        Serial.println(camera.exception.toString());
+
+    Serial.println("Camera OK");
+    Serial.println("ToF OK");
+    Serial.println("WiFi OK");
+    Serial.println("MjpegStream OK");
+    Serial.println(mjpeg.address());
+}
+
+/**
+ *
+ */
+void loop() {
+    // nothing to do here, MJPEG server runs in background
+}
+
+
+/**
+ * Apply your custom processing to pixels
+ * then encode to JPEG.
+ * You will need to modify this
+ */
+void reencode_frame(WiFiClient *client, camera_fb_t* frame) {
+    // log how much time elapsed from last frame
+    const size_t now = millis();
+    const uint16_t height = camera.resolution.getHeight();
+    const uint16_t width = camera.resolution.getWidth();
+
+    ESP_LOGI("benchmark", "%d ms elapsed from last frame", now - tick);
+    tick = now;
+
+    // frame->buf contains RGB565 data
+    // that is, 2 bytes per pixel
+    //
+    // in this test, we're going to drop the B component
+    // feel free to replace this with your own code
+    for (uint16_t y = 0; y < height; y++) {
+        uint16_t *row = (uint16_t*) (frame->buf + width * 2 * y);
+
+        for (uint16_t x = 0; x < width; x++) {
+            // read pixel and parse to R, G, B components
+            const uint16_t pixel = row[x];
+            uint16_t r = (pixel >> 11);
+            uint16_t g = (pixel >> 5) & 0b111111;
+            uint16_t b = pixel & 0b11111;
+
+            // actual work: drop B component
+            b = 0;
+
+            // re-pack to RGB565
+            row[x] = (r << 11) | (g << 5) | b;
+        }
+    }
+
+    // encode to jpeg
+    uint8_t quality = 90;
+    frame2jpg_cb(frame, quality, &buffer_jpeg, NULL);
+    ESP_LOGI("var_dump", "JPEG size=%d", jpeg_length);
+}
+
+
+/**
+ * Put JPEG-encoded data back into the original frame
+ * (you don't have to modify this)
+ */
+size_t buffer_jpeg(void *arg, size_t index, const void* data, size_t len) {
+    if (index == 0) {
+        // first MCU block => reset jpeg length
+        jpeg_length = 0;
+    }
+
+    if (len == 0) {
+        // encoding is done
+        camera.frame->len = jpeg_length;
+        return 0;
+    }
+
+    jpeg_length += len;
+
+    // override input data
+    memcpy(camera.frame->buf + index, (uint8_t*) data, len);
+
+    return len;
+}