add mjpeg support to camera buffer decoder by injecting a default huffman table

Author: underdoeg

modules/camera/buffer_decoder.cpp

@@ -202,10 +202,63 @@ JpegBufferDecoder::JpegBufferDecoder(CameraFeed *p_camera_feed) :
 		BufferDecoder(p_camera_feed) {
 }
 
+static const uint8_t huffman_table[] = {
+	// Huffman table
+	0xff, 0xc4, 0x01, 0xa2, 0x00, 0x00, 0x01, 0x05, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a,
+	0x0b, 0x01, 0x00, 0x03, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x01, 0x00, 0x00, 0x00,
+	0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x0a, 0x0b, 0x10, 0x00,
+	0x02, 0x01, 0x03, 0x03, 0x02, 0x04, 0x03, 0x05, 0x05, 0x04, 0x04, 0x00, 0x00, 0x01, 0x7d, 0x01,
+	0x02, 0x03, 0x00, 0x04, 0x11, 0x05, 0x12, 0x21, 0x31, 0x41, 0x06, 0x13, 0x51, 0x61, 0x07, 0x22,
+	0x71, 0x14, 0x32, 0x81, 0x91, 0xa1, 0x08, 0x23, 0x42, 0xb1, 0xc1, 0x15, 0x52, 0xd1, 0xf0, 0x24,
+	0x33, 0x62, 0x72, 0x82, 0x09, 0x0a, 0x16, 0x17, 0x18, 0x19, 0x1a, 0x25, 0x26, 0x27, 0x28, 0x29,
+	0x2a, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4a,
+	0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x63, 0x64, 0x65, 0x66, 0x67, 0x68, 0x69, 0x6a,
+	0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8a,
+	0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, 0xa8,
+	0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6,
+	0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8, 0xd9, 0xda, 0xe1, 0xe2, 0xe3,
+	0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, 0xf8, 0xf9,
+	0xfa, 0x11, 0x00, 0x02, 0x01, 0x02, 0x04, 0x04, 0x03, 0x04, 0x07, 0x05, 0x04, 0x04, 0x00, 0x01,
+	0x02, 0x77, 0x00, 0x01, 0x02, 0x03, 0x11, 0x04, 0x05, 0x21, 0x31, 0x06, 0x12, 0x41, 0x51, 0x07,
+	0x61, 0x71, 0x13, 0x22, 0x32, 0x81, 0x08, 0x14, 0x42, 0x91, 0xa1, 0xb1, 0xc1, 0x09, 0x23, 0x33,
+	0x52, 0xf0, 0x15, 0x62, 0x72, 0xd1, 0x0a, 0x16, 0x24, 0x34, 0xe1, 0x25, 0xf1, 0x17, 0x18, 0x19,
+	0x1a, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x43, 0x44, 0x45, 0x46,
+	0x47, 0x48, 0x49, 0x4a, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, 0x59, 0x5a, 0x63, 0x64, 0x65, 0x66,
+	0x67, 0x68, 0x69, 0x6a, 0x73, 0x74, 0x75, 0x76, 0x77, 0x78, 0x79, 0x7a, 0x82, 0x83, 0x84, 0x85,
+	0x86, 0x87, 0x88, 0x89, 0x8a, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x9a, 0xa2, 0xa3,
+	0xa4, 0xa5, 0xa6, 0xa7, 0xa8, 0xa9, 0xaa, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xba,
+	0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0xc8, 0xc9, 0xca, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, 0xd8,
+	0xd9, 0xda, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, 0xe8, 0xe9, 0xea, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6,
+	0xf7, 0xf8, 0xf9, 0xfa
+};
+
+inline int find_byte_sequence(uint8_t *buffer, int buffer_size, uint8_t a, uint8_t b) {
+	for (int i = 0; i < buffer_size - 1; i++) {
+		if (buffer[i] == a && buffer[i + 1] == b) {
+			return i;
+		}
+	}
+	return -1;
+}
+
 void JpegBufferDecoder::decode(StreamingBuffer p_buffer) {
 	image_data.resize(p_buffer.length);
 	uint8_t *dst = (uint8_t *)image_data.ptrw();
-	memcpy(dst, p_buffer.start, p_buffer.length);
+
+	// search for Start of Frame (SOF0) marker
+	int header_end_index = find_byte_sequence((uint8_t *)p_buffer.start, p_buffer.length, 0xff, 0xc0);
+	int huff_index = find_byte_sequence((uint8_t *)p_buffer.start, header_end_index, huffman_table[0], huffman_table[1]);
+	if (huff_index == -1) {
+		// inject default huffman table before the header end index
+		image_data.resize(p_buffer.length + sizeof(huffman_table));
+		memcpy(dst, p_buffer.start, header_end_index);
+		memcpy(dst + header_end_index, huffman_table, sizeof(huffman_table));
+		memcpy(dst + header_end_index + sizeof(huffman_table), (uint8_t *)p_buffer.start + header_end_index, p_buffer.length - header_end_index);
+	} else {
+		memcpy(dst, p_buffer.start, p_buffer.length);
+	}
+
 	if (image->load_jpg_from_buffer(image_data) == OK) {
 		camera_feed->set_rgb_image(image);
 	}

modules/camera/camera_feed_linux.cpp

@@ -199,6 +199,8 @@ void CameraFeedLinux::_read_frame() {
 		return;
 	}
 
+	buffers[buffer.index].length = buffer.bytesused ? buffer.bytesused : buffer.length;
+
 	buffer_decoder->decode(buffers[buffer.index]);
 
 	if (ioctl(file_descriptor, VIDIOC_QBUF, &buffer) == -1) {