StepV <= 1;                  else                     StepV <= 0;                  end if;                     NDe <= '0';                  RFDInt <= '0';               when 1 => --Feeding of DCT1 with 64 pixels                  if RFD = '1' then --DCT1 ready for data (RFD)                     NDe <= '1';                     ND <= NDe; --this way we delay ND one cycle to synchronize data                     if RFDInt = '0' then                        case Bloque is                           when "00" => --block Y                              DIND <= doutY(7 downto 0);                            when "01" => --block Cb                              DIND <= doutCb(7 downto 0);                            when others => --can only be block Cr                              DIND <= doutCr(7 downto 0);                         end case;                     else                        DIND <= RFDIntData; --to recover the "lost" cycle because RFD was 0 (if the DCT was such that RFD were 0 for more than a cycle it would be necessary to change this part)                        RFDInt <= '0';                     end if;                        if Columna(2 downto 0) = "111" then                        Columna := Columna(9 downto 3) & "000";                        Linea := Linea + 1;                        if Linea(2 downto 0) = "000" then --we've finished this StepV, now we'll wait for the results                           StepV <= 2; --we shall go to StepV 2 with the first column of the block                           Linea(3) := not Linea(3); --makes it rest in current block                           Primera := '1'; --to not let StepV 2 change Linea or Column in its 1st cycle because they already have adequate values                        end if;                        else                        Columna := Columna + 1;                     end if;                     else                     --to not lose the just read pixel (rememer that reads are ahead of their time!!)                     RFDInt <= '1';                     case Bloque is                        when "00" => --block Y                           RFDIntData <= doutY(7 downto 0);                         when "01" => --block Cb                           RFDIntData <= doutCb(7 downto 0);                         when others => --can only be block Cr                           RFDIntData <= doutCr(7 downto 0);                      end case;                     --ND <= '0';                  end if;                  weY2 <= '0';                  weCb2 <= '0';                  weCr2 <= '0';                  addrQ <= Base; --DC Coefficient's Q (Base + Linea*8 + Columna)                  QDC := (others => '0');               when 2 => --we receive the data, quantize it, truncate it and save them back to the buffer                  --watch out because DCT1 outputs data column-wise (feeding was row-wise)                  NDe <= '0'; --it stayed high while sending data byte                  ND <= NDe;                  case Bloque is  --needed to send the last data of the block (it is alright!!!)                     when "00" => --block Y                        DIND <= doutY(7 downto 0);                      when "01" => --block Cb                        DIND <= doutCb(7 downto 0);                      when others => --can only be block Cr                        DIND <= doutCr(7 downto 0);                   end case;                                                      if RDY = '1' then --output data ready!!                     if QDC /= 0 then                        DCTQ := MultiplierQ(DOUTD(14 downto 3), QDC);                        QDC := (others => '0');                     else                                DCTQ := MultiplierQ(DOUTD(14 downto 3), DOUTQ); --multiply the DCT coefficient times Qyx fraction's numerator                     end if;                     --if DCTQ(24) = '0' then --it is positive, let's round                        DCTQ(24 downto 14) := DCTQ(24 downto 14) + DCTQ(13); --round to nearest integer                     --end if;                        --if DCTQ(24 downto 13) = "111111111111" then --it is less or equal than -0.5, roung to 0                     --   DCTQ(24 downto 13) := "000000000000"; --or else it will be read as -1                     --end if;                     case Bloque is --the "+ DCTQ(13)" is the nearest integer round!                        when "00" => --block Y                           dinY2 <= DCTQ(24) & DCTQ(24 downto 14);-- + DCTQ(13); --we divide (shifting right) by the general Q coefficient denominator (16384) and save the quantized coefficient                           --sign-extension                           weY2 <= '1';                        when "01" => --block Cb                           dinCb2 <= DCTQ(24) & DCTQ(24 downto 14);-- + DCTQ(13); --we divide (shifting right) by the general Q coefficient denominator (16384) and save the quantized coefficient                           weCb2 <= '1';                        when others => --can only be block Cr                           dinCr2 <= DCTQ(24) & DCTQ(24 downto 14);-- + DCTQ(13); --we divide (shifting right) by the general Q coefficient denominator (16384) and save the quantized coefficient                           weCr2 <= '1';                     end case;                                                               --write column-wise                     if Linea(2 downto 0) = "111" and Primera = '0' then --have we reached this line's end?                        --Primera is used for the first cycle of StepV2 in which Columna and Linea arrive with the right value                        --so they need not be changed in order to get the correct address                        Linea := Linea(3) & "000";                        Columna := Columna + 1;                     else                        if Primera = '1' then                           Primera := '0';                        else                              Linea := Linea + 1;                           if Linea(2 downto 0) = "111" and Columna(2 downto 0) = "111" then --we have finished this StepV, now we must Huffman encode                               StepV <= 3;                           end if;                           end if;                        end if;                                          --the following code is because we must load one cycle early the addrQ so that in the                     --current cycle we can have the right Q coefficient for current Linea and Columna values                     if Linea(2 downto 0) = "110" then --have we reached the end?                        --next coeff. is Linea 0 of the Coeff. Table and Columna is current plus one                        addrQ <= Base + Columna(2 downto 0) + 2; --Base + Linea*8 + Columna --> remember coefficient table is 8x8                     else                        --next coeff is next Linea of the Coeff. Table and current Columna                        addrQ <= Base + ((Linea(2 downto 0) + 2) & "000") + Columna(2 downto 0); --Base + Linea*8 + Columna                     end if;                                       else                     --during Latency cycles we will be here waiting until RDY is 1                     --and also every X cycles when RDY becomes 0 for one cycle                     if QDC = 0 and addrQ = Base then --only happens when we enter this StepV from the previous one                        QDC := DOUTQ; --save the DC value because Q reading must be ahead by two cycles now                        addrQ <= Base + "1000"; --Base + Linea*8 + Columna (Linea=1, Columna=0)                     end if;                        weY2 <= '0';                     weCr2 <= '0';                     weCb2 <= '0';                  end if;                  when 3 =>                  weY2 <= '0';                  weCr2 <= '0';                  weCb2 <= '0';                  --Make the "pointers" Linea and Columna point to the beginning of the next block                  --must do it here because in the last cycle of StepV2, when StepV becomes 3, Linea and Columna                  --must maintain their value                  Linea := Linea(3) & "000";                  Columna := Columna + 1;                  if LumaBlock = '1' then --if we are processing the luminance block we can only save it when we have processed the 4 ones                     --that compose the 2x2 block of subsampling, there is no problem with the order of the chroma ones because these ones too                     --are saved when we have averaged four and that is controlled by the process RGB2YCbCr                     if Linea(3) = '1' and Columna(3) = '0' then --checked, it is alright (remember it points to the next block)                        StepV <= 4;                        Elemento := "00"; --process the first square (8x8 block) of the 2x2 luminance block (16x16 pixels, 2x2 squares)                        --Ready Linea and Columna to read element 00 that Huffman will receive                        Linea := (others => '0');                        Columna := (Columna(9 downto 4) - 1) & "0000";                     else --the three first squares of the 2x2 luminance block are not sent to Huffman yet (subsampling requirements)                        StepV <= 0;                        Done <= '1';                     end if;                  else                     Columna := Columna - 1;                     Columna := Columna(9 downto 3) & "000"; --it is alright, because Columna arrives already adjusted to Cb and Cr.                     StepV <= 4;                  end if;                  WriteAdditionalBits <= '0';               when 4 => --with this dummy cycle we give time to the memory to give us address 0                  --for the DC coefficient                  weY2 <= '0';                  weCr2 <= '0';                  weCb2 <= '0';                  Save <= '0'; --just in case we left it high in last step                  we <= '0';                  StepV <= 5;                 when 5 => --Linea and Columna point to the beginning of the block                  --If we change Linea and/or Columna in cycle 0 of this section, then the new address will                  --be sent to memory in cycle 1 and in cycle 2 doutX will have the asked data, so careful!!                  case Bloque is                     when "00" => --block Y                        Coef := doutY;                      when "01" => --block Cb                        Coef := doutCb;                      when others => --can only be block Cr                        Coef := doutCr;                   end case;                                    we <= '0';                     if Done = '0' then --this way it does not go to look for the DC when we change Block (upsetting FirstDC)                  if Save = '0' then                     if WriteAdditionalBits = '0' then                        if Coeficiente = 0 then                            --The previous component is read from the buffer varying Linea and Columna                           if IniDC = '1' then --we've not yet obtained the previous DC to calculate the difference                              if Linea = "0000" and Columna = "000000000" and FirstDC = '1' and GetPrevDC = '1' then --must do it this way                                 --or else the luminance, which has 4 blocks in its first Huffmanear takes DC=0 for all                                 --GetPrevDC = 1 is so that execution doesnt get here if in the previous cycle GetPrevDC became zero in the bottom "if"                                 --and put Linea and Columna to zero                                 --we are in the first block of the image, PrevDC is zero                                 if Bloque = "10" then --if we are in the last, we zero it                                    FirstDC := '0'; --because it has already been used by the three components (Y,Cb,Cr)                                 end if;                                 PrevDC := (others => '0');                                 IniDC := '0';                              else                                 if GetPrevDC = '1' then                                    ColBk := Columna; --save the values of Linea and Columna                                    LinBk := Linea;                                                                        --Must obtain the quantized DC coefficient of the last processed block                                    --as stated by specification, but actually the last block is indicated by MCU                                    if Columna(9 downto 3) = "0000000" then --first block of the row?                                       if LumaBlock = '1' then                                          if Elemento = "00" then                                             --Remember that DCTs are done when only the last line of all is left to be written in the block                                             --so the DC of the previous block has already been overwritten, that's why we use LastBlockDCY                                             PrevDC := LastBlockDCY;                                             IniDC := '0'; --this way we skip the next StepV                                          else --Elemento 10 need the DC of Elemento 01                                             Linea(3) := '0';                                                                                          Columna(3) := '1';                                          end if;                                          else --in chrominance ImgColumns has half the image's columns!                                          if Bloque = "01" then --block Cb                                             PrevDC := LastBlockDCCb;                                          else --10 = block Cr                                             PrevDC := LastBlockDCCr;                                          end if;                                          IniDC := '0';                                       end if;                                       else                                       if LumaBlock = '1' then                                          case Elemento is                                             when "00" => --DC of previous element 11                                                Columna := (Columna(9 downto 3)-1) & "000";                                                Linea(3) := '1';                                             when "01" => --DC of element 00                                                Columna(3) := '0';                                                Linea(3) := '0';                                             when "10" => --DC of element 01                                                Columna(3) := '1';                                                Linea(3) := '0';                                             when others => --11 DC of element 10                                                Columna(3) := '0';                                                Linea(3) := '1';                                          end case;                                             else                                                                                       Columna := (Columna(9 downto 3) - 1) & "000"; --first column of previous block                                       end if;                                       end if;                                    StepV <= 4; --wait one cycle for PrevDC                                    GetPrevDC := '0';                                 else                                       GetPrevDC := '1'; --we rise it for the next block                                    IniDC := '0';                                    PrevDC := Coef;                                    Linea := LinBk;                                    Columna := ColBk;                                    StepV <= 4; --wait one cycle to get back the current DC component to operate with it                                 end if;                                                      end if;                           else --IniDC = '0' that is, we now have the PrevDC                                GetPrevDC := '1'; --we rise it for the second block after the first one of the image                              --in this "if" we see if this is the last block in the buffer and in that case                              --save its DC component                              if LumaBlock = '1' then                                 if Columna(9 downto 3) = ImgColumns(9 downto 3) and Elemento="11" then                                    LastBlockDCY := Coef;                                 end if;                              else                                 if Columna(9 downto 3) = ImgColumns(9 downto 4) then                                    if Bloque = "01" then --block Cb                                       LastBlockDCCb := Coef;                                    else --block Cr                                       LastBlockDCCr := Coef;                                    end if;