<PAGE>   1

      AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON JUNE 6, 2000
                         REGISTRATION NO. 333-__________
--------------------------------------------------------------------------------
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                         -------------------------------
                                  FORM S-4MEF
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                            ------------------------
                                  HARMONIC INC.
             (Exact name of registrant as specified in its charter)


<TABLE>
<S>                                  <C>                          <C>
         DELAWARE                              3663                             77-0201147
(State or other jurisdiction of          (Primary Standard        (I.R.S. Employer Identification Number)
incorporation or organization)       Industrial Classification                   
                                           Code Number)
</TABLE>


                       549 BALTIC WAY, SUNNYVALE, CA 94089
                                 (408) 542-2500
    (Address, including zip code, and telephone number, including area code,
                  of registrant's principal executive offices)

                                 ANTHONY J. LEY
                      PRESIDENT AND CHIEF EXECUTIVE OFFICER
                                  HARMONIC INC.
                       549 BALTIC WAY, SUNNYVALE, CA 94089
                                 (408) 542-2500
 (Name, address, including zip code, and telephone number, including area code,
                              of agent for service)

                                 WITH COPIES TO:

<TABLE>
    <S>                                    <C>
       LAWRENCE CALOF, ESQ.                      LARRY W. SONSINI, ESQ.
          STAN SZE, ESQ.                            KELLY BOYD, ESQ.
    GIBSON, DUNN & CRUTCHER LLP            WILSON, SONSINI, GOODRICH & ROSATI
       1530 PAGE MILL ROAD                     PROFESSIONAL CORPORATION
     PALO ALTO, CA 94304-1125                      650 PAGE MILL ROAD
         (650) 849-5300                        PALO ALTO, CA 94304-1050
                                                    (650) 493-9300
</TABLE>


                            ------------------------

     APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED SALE TO THE PUBLIC: AS SOON AS
PRACTICABLE AFTER THE EFFECTIVE DATE OF THIS REGISTRATION STATEMENT WHICH
RELATES TO THE ISSUANCE OF COMMON STOCK OF HARMONIC INC. IN THE MERGER OF C-CUBE
MICROSYSTEMS INC. INTO HARMONIC INC. PURSUANT TO AN AMENDED AND RESTATED
AGREEMENT AND PLAN OF MERGER AND REORGANIZATION DATED AS OF DECEMBER 9, 1999.

                            ------------------------

If the securities being registered on this Form are being offered in connection
with the formation of a holding company and there is compliance with General
Instruction G, please check the following box. [ ]

If this Form is filed to register additional securities for an offering pursuant
to Rule 462(b) under the Securities Act, check the following box and list the
Securities Act registration statement number of the earlier effective
registration statement for the same offering. [X] 333-33148 

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under
the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [ ] 

If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [ ]

                           -------------------------

                        CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
========================================================================================================================
                                                        PROPOSED MAXIMUM       PROPOSED MAXIMUM
SECURITIES TO BE REGISTERED            AMOUNT TO         OFFERING PRICE           AGGREGATE              AMOUNT OF
  TITLE OF EACH CLASS OF            BE REGISTERED(1)       PER SHARE           OFFERING PRICE(2)     REGISTRATION FEE(2)
------------------------------------------------------------------------------------------------------------------------
<S>                                    <C>                   <C>                 <C>                     <C>         
Common Stock, $.001 par value......    1,628,775             N/A                 $31,783,174             $8,391      
========================================================================================================================
</TABLE>


(1)  The Registrant, Harmonic Inc. ("Harmonic") and C-Cube Microsystems Inc.
     ("C-Cube Microsystems"), previously filed a joint proxy/registration
     statement on Form S-4 (Commission File No. 333-33148) to cover 25,371,225
     shares (the "Initial Shares") of Harmonic's common stock, $.001 par value
     ("Harmonic Common Stock"), issuable in connection with the merger of C-Cube
     Microsystems into Harmonic. Harmonic is filing this registration statement
     on Form S-4MEF pursuant to Rule 462(b) with respect to an additional 
     1,628,775 shares of Harmonic Common Stock issuable in connection with the 
     merger based on an increase in the estimated number of shares of common
     stock of C-Cube Microsystems outstanding at closing.

(2)  At the exchange ratio of 0.5427, 3,001,244 shares of C-Cube Microsystems
     common stock would be cancelled in the transaction in exchange for the
     additional 1,628,775 shares of Harmonic Common Stock registered hereby. The
     Proposed Maximum Aggregate Offering Price and the Amount of Registration
     Fee are based on this number of shares of C-Cube Microsystems common stock
     and, pursuant to Rule 457(f) under the Securities Act of 1933, as amended,
     the book value of such securities computed as of the latest practicable
     date prior to the date of filing the registration statement in the amount
     of $10.59. Harmonic previously paid a registration fee of $513,442 in
     connection with the registration of the Initial Shares. In accordance with
     Rule 457(a), the shares of C-Cube Microsystems common stock that would be
     cancelled in the transaction in exchange for the Initial Shares have been
     excluded from the calculation of the amount of the registration fee payable
     in connection with this registration statement.


<PAGE>   2





         Explanatory Note and Incorporation of Information by Reference

     This Registration Statement is being filed pursuant to Rule 462(b) under
the Securities Act of 1933, as amended, and relates to the offering of shares of
common stock of Harmonic Inc. ("Harmonic") in connection with its acquisition of
C-Cube Microsystems Inc. as described in the joint proxy/registration statement
on Form S-4, Registration No. 333-33148, as amended (the "Prior Registration
Statement"). This Registration Statement is being filed to register an
additional 1,628,775 shares of common stock of Harmonic for issuance in
connection with that acquisition. The contents of the Prior Registration
Statement, including all exhibits thereto, are hereby incorporated by reference.

                                    EXHIBITS


<TABLE>
<S>       <C>    
5.1       Opinion of Gibson, Dunn & Crutcher LLP as to the legality of the
          securities being registered

8.1       Opinion of Gibson, Dunn & Crutcher LLP as to tax matters

8.2       Opinion of Wilson, Sonsini, Goodrich & Rosati, Professional
          Corporation as to tax matters

23.1      Consent of Deloitte & Touche LLP

23.2      Consent of PricewaterhouseCoopers LLP

23.3      Consent of Gibson, Dunn & Crutcher LLP (included in Exhibit 5.1)

23.4      Consent of Gibson, Dunn & Crutcher LLP (included in Exhibit 8.1)

23.5      Consent of Wilson, Sonsini, Goodrich & Rosati, Professional
          Corporation (included in Exhibit 8.2)

24        Power of Attorney (Incorporated by reference to Harmonic's
          Registration Statement on Form S-4, File No. 333-33148)
</TABLE>


<PAGE>   3
                                   SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has
duly caused this Registration Statement to be signed on its behalf by the
undersigned, thereunto duly authorized, in the City of Palo Alto, State of
California, on June 6, 2000.

                                   HARMONIC INC.


                                   By: /s/ Anthony J. Ley
                                      -----------------------------------------
                                   Name: Anthony J. Ley
                                   Title: President and Chief Executive Officer


Pursuant to the requirements of the Securities Act of 1933, this Registration
Statement has been signed by the following persons in the capacities and on the
dates indicated.


<TABLE>
<CAPTION>
                 SIGNATURE                                         TITLE                            DATE
<S>                                          <C>                                               <C>

           /s/ Anthony J. Ley                President and Chief Executive Officer             June 6, 2000
--------------------------------------------         (Principal Executive Officer)
               Anthony J. Ley 

                     *                       Chief Financial Officer (Principal Financial      June 6, 2000
--------------------------------------------            and Accounting Officer)
              Robin N. Dickson

                     *                                      Director                           June 6, 2000
--------------------------------------------
              Moshe Nazarathy

                     *                                      Director                           June 6, 2000
--------------------------------------------
              E. Floyd Kvamme

                     *                                      Director                           June 6, 2000
--------------------------------------------
               David A. Lane

                     *                                      Director                           June 6, 2000
--------------------------------------------
              Barry D. Lemieux

                     *                                      Director                           June 6, 2000
--------------------------------------------
             Michel L. Vaillaud
</TABLE>



* By: /s/ Anthony J. Ley
      --------------------------------------
Name: Anthony J. Ley
Title: Attorney-In-Fact





<PAGE>   4

                                  EXHIBIT INDEX


<TABLE>
<S>       <C>    
5.1       Opinion of Gibson, Dunn & Crutcher LLP as to the legality of the
          securities being registered

8.1       Opinion of Gibson, Dunn & Crutcher LLP as to tax matters

8.2       Opinion of Wilson, Sonsini, Goodrich & Rosati, Professional
          Corporation as to tax matters

23.1      Consent of Deloitte & Touche LLP

23.2      Consent of PricewaterhouseCoopers LLP

23.3      Consent of Gibson, Dunn & Crutcher LLP (included in Exhibit 5.1)

23.4      Consent of Gibson, Dunn & Crutcher LLP (included in Exhibit 8.1)

23.5      Consent of Wilson, Sonsini, Goodrich & Rosati, Professional
          Corporation (included in Exhibit 8.2)

24        Power of Attorney (Incorporated by reference to Harmonic's
          Registration Statement on Form S-4, File No. 333-33148)
</TABLE>






<PAGE>   1


                                  June 2, 2000





(650) 849-5318                                                     C 41507-00001


Harmonic Inc.
549 Baltic Way
Sunnyvale, CA 94089

         Re: Registration Statement on Form S-4

Gentlemen:

     We have acted as counsel for Harmonic, Inc., a Delaware corporation (the
"Company"), in connection with the preparation and filing with the Securities
and Exchange Commission (the "Commission") under Rule 462(b) of the Securities
Act of 1933, as amended (the "Act"), of the above-captioned Registration
Statement on Form S-4 (the "Registration Statement"), relating to the
registration of 1,628,775 shares of the Company's Common Stock, par value $.001
per share (the "Shares"). The Company proposes to issue the Shares in exchange
for shares of C-Cube Microsystems Inc.'s ("C-Cube Microsystems") Common Stock,
par value $0.001 per share. In connection therewith, we have examined, among
other things, the Registration Statement, as well as the proceedings and other
actions taken by the Company in connection with the authorization of the Shares
and such other matters as we deemed necessary for purposes of rendering this
opinion.

     Based on the foregoing, and in reliance thereon, we are of the opinion that
(i) the Shares have been duly authorized and (ii) upon issuance of the Shares in
connection with the merger of C-Cube
 Microsystems into the Company as described
in the Registration Statement and the Prospectus constituting a part thereof
(the "Prospectus"), the Shares will be validly issued, fully paid and
non-assessable.

     The Company is a Delaware corporation. We are not admitted to practice in
Delaware. However, we are familiar with the Delaware General Corporation Law and
have made such review thereof as we consider necessary for the purpose of this
opinion. Subject to the foregoing, this opinion is limited to the present laws
of the State of Delaware and to the present federal laws of the United States of
America.

     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to this firm under the heading
"Legal Matters" contained in the Prospectus. In giving this consent, we do not
admit that we are within the category of persons whose consent is required under
Section 7 of the Act or the General Rules and Regulations of the Securities and
Exchange Commission.

                                   Sincerely,

                                   /s/ Gibson, Dunn & Crutcher LLP

                                   Gibson, Dunn & Crutcher LLP

LC/SS/ss





<PAGE>   1
                                                                     EXHIBIT 8.1



                    [GIBSON, DUNN & CRUTCHER LLP LETTERHEAD]



                                  June 5, 2000


(213) 229-7000                                                     C 41507-00001


Harmonic Inc.
549 Baltic Way
Sunnyvale, California 94089

     Re:  Acquisition of C-Cube Microsystems Inc.

Ladies and Gentlemen:

     We have acted as counsel to Harmonic Inc., a Delaware corporation
("HARMONIC"), in connection with the preparation and execution of the Amended
and Restated Agreement and Plan of Merger and Reorganization (the "MERGER
AGREEMENT"), dated as of December 9, 1999, by and between Harmonic and C-Cube
Microsystems Inc., a Delaware corporation ("C-CUBE"). Pursuant to the Merger
Agreement, C-Cube has merged with and into Harmonic, with Harmonic surviving the
merger (the "MERGER"). The Merger and certain proposed transactions incident
thereto are described in the Registration Statement on Form S-4 (the
"REGISTRATION STATEMENT") of Harmonic, which includes the Joint Proxy
Statement/Prospectus/Information Statement (the "JOINT PROXY STATEMENT") of
C-Cube and Harmonic, that was filed with the Securities and Exchange Commission
under the Securities Act of 1933 and which became effective on March 24, 2000.

     You have requested our opinion regarding certain federal income tax
consequences of the Merger. In rendering this opinion,
 we have assumed and
relied upon (without any independent investigation):

     1.   The truth and accuracy of the statements, covenants, representations
and warranties contained (a) in the Merger Agreement, (b) in the representations
received from Harmonic and C-Cube (the "TAX REPRESENTATION LETTERS") that have
been provided to us and dated as of May 3, 2000, and (c) in the Registration
Statement;

<PAGE>   2
Harmonic Inc.
June 5, 2000
Page 2


     2.   that the Merger was consummated in accordance with the Merger
Agreement, without any waiver, breach or amendment of any material provisions of
the Merger Agreement, the effectiveness of the Merger under applicable state
law, and the performance of all covenants contained in the Merger Agreement and
the Tax Representation Letters without waiver or breach of any material
provisions thereof, in each case except as otherwise provided in the Waiver
Agreement entered into between Harmonic and C-Cube as of April 21, 2000;

     3.   the accuracy of any representation or statement made "to the knowledge
of" or similarly qualified without such qualification, and as to all matters in
which a person or entity is making a representation, that such person or entity
is not a party to, does not have, and is not aware of, any plan, intention,
understanding or agreement inconsistent with such representation, and there is
no such plan, intention, understanding, or agreement inconsistent with such
representation;

     4.   the reporting of the Merger as a reorganization, within the meaning of
Section 368(a) of the Internal Revenue Code of 1986, as amended (the "CODE"), by
Harmonic and C-Cube in their federal income tax returns;

     5.   the authenticity of original documents (including signatures),
conformity to the originals of documents submitted to us as copies, and due
execution and delivery of all documents where due execution and delivery are
prerequisites to effectiveness thereof; and

     6.   the absence of any occurrence since the date of the Tax Representation
Letters that could have caused any of the declarations and representations
contained in those letters to be untrue, incorrect, or incomplete in any respect
at any time since such date.

     Based upon the foregoing, the discussion contained in the Joint Proxy
Statement under the caption "Material Federal Income Tax Consequences of the
Merger," subject to the limitations and qualifications described therein and
herein, and as of March 24, 2000, is our opinion with respect to the federal
income tax consequences generally applicable to the Merger.

     This opinion represents our best judgment regarding the application of
federal income tax laws under the Code, existing judicial decisions,
administrative regulations and published rulings and procedures. Our opinion is
not binding upon the Internal Revenue Service or the courts, and there is no
assurance that the Internal Revenue Service will not successfully assert a
contrary position. Furthermore, no assurance can be given that future
legislative, judicial or administrative changes, on either a prospective or
retroactive basis, would not adversely affect the accuracy of the conclusions
stated herein. We undertake no responsibility to advise you of any new
developments in the application or interpretation of the federal income tax
laws. Furthermore, in the event any one of the statements, covenants,
representations, warranties or assumptions upon which we have relied to issue
this opinion is incorrect, our opinion might be adversely affected and may not
be relied upon.

<PAGE>   3
Harmonic Inc.
June 5, 2000
Page 3


     This opinion addresses only the matters described above, and does not
address any other federal, state, local or foreign tax consequences that may
result from the Merger or any other transaction (including any transaction
undertaken in connection with the Merger).

     This opinion may not be relied upon for any other purpose or by any other
person or entity, and may not be furnished to, quoted to or by or relied upon by
any other person or entity, without our prior written consent.

                                       Very truly yours,


                                       /s/ GIBSON, DUNN & CRUTCHER LLP 
                                       -------------------------------
                                       Gibson, Dunn & Crutcher LLP



<PAGE>   1
                                                                     Exhibit 8.2

                                [WSGR LETTERHEAD]

                                  June 5, 2000


C-Cube Microsystems Inc.
1778 McCarthy Boulevard
Milpitas, CA 95035

     Re:  Registration Statement on Form S-4

Ladies and Gentlemen:

     We have acted as counsel to C-Cube Microsystems Inc., a Delaware
corporation ("C-Cube"), in connection with the preparation and execution of the
Amended and Restated Agreement and Plan of Merger and Reorganization (the
"Merger Agreement"), dated as of December 9, 1999, by and between C-Cube and
Harmonic Inc., a Delaware corporation ("Harmonic"). Pursuant to the Merger
Agreement, C-Cube has merged with and into Harmonic, with Harmonic surviving the
merger (the "Merger"). The Merger and certain proposed transactions incident
thereto are described in the Registration Statement on Form S-4 (the
"Registration Statement") of Harmonic, which includes the Joint Proxy
Statement/Prospectus/Information Statement of C-Cube and Harmonic ("Joint Proxy
Statement"), which was filed with the U.S. Securities and Exchange Commission
under the Securities Act of 1933 and which became effective on March 24, 2000.

     You have requested our opinion regarding certain federal income tax
consequences of the Merger. In connection with rendering this opinion, we have
assumed and relied
 upon (without any independent investigation):

     1.   The truth and accuracy of the statements, covenants, representations
and warranties contained in the Merger Agreement, in the representations
received by us from Harmonic and C-Cube dated as of May 3, 2000 (the "Tax
Representation Letters") and in the Registration Statement;

     2.   Consummation of the Merger in accordance with the Merger Agreement,
without any waiver, breach or amendment of any material provisions of the Merger
Agreement, the effectiveness of the Merger under applicable state law, and the
performance of all covenants contained in the Merger Agreement and the Tax
Representation Letters without waiver or breach of any material provisions
thereof, in each case except as otherwise provided in the Waiver Agreement
entered into between Harmonic and C-Cube dated as of April 21, 2000;

     3.   The accuracy of any representation or statement made "to the knowledge
of" or similarly qualified without such qualification, and as to all matters in
which a person or entity is making a representation, that such person or entity
is not a party to, does not have, or is not aware of, any plan, intention,
understanding or agreement inconsistent with such representation, and there is
no such plan, intention, understanding, or agreement inconsistent with such
representation;


<PAGE>   2

     4.   The reporting of the Merger as a reorganization, within the meaning of
Section 368(a) of the Internal Revenue Code of 1986, as amended (the "Code"), by
Harmonic in its federal income return;

     5.   The authenticity of original documents (including signatures),
conformity to the originals of documents submitted to us as copies, and due
execution and delivery of all documents where due execution and delivery are
prerequisites to effectiveness thereof; and

     6.   The absence of any occurrence since the date of the Tax Representation
Letters, which change could have caused any of the declarations and
representations contained in those letters to be untrue, incorrect or incomplete
in any respect at any time since that date.

     Based upon the foregoing, the discussion contained in the Joint Proxy
Statement under the caption "Material Federal Income Tax Consequences of the
Merger," subject to the limitations and qualifications described therein and
herein, and as of March [24], 2000, is our opinion with respect to the material
United States federal income tax consequences generally applicable to the
Merger.

     This opinion represents our best judgment regarding the application of
federal income tax laws under the Code, existing judicial decisions,
administrative regulations and published rulings and procedures. Our opinion is
not binding upon the Internal Revenue Service or the courts, and there is no
assurance that the Internal Revenue Service will not successfully assert a
contrary position. Furthermore, no assurance can be given that future
legislative, judicial or administrative changes, on either a prospective or
retroactive basis, would not adversely affect the accuracy of the conclusions
stated herein. We undertake no responsibility to advise you of any new
developments in the application or interpretation of the federal income tax
laws. Furthermore, in the event any one of the statements, covenants,
representations, warranties or assumptions upon which we have relied to issue
this opinion is incorrect, our opinion might be adversely affected and may not
be relied upon.

     This opinion addresses only the matters described above, and does not
address any other federal, state, local or foreign tax consequences that may
result from the Merger or any other transaction undertaken in connection with
the Merger.

         This opinion is rendered only to you and is solely for your benefit in
connection with filing the Registration Statement with the Securities and
Exchange Commission. This opinion may not be relied upon for any other purpose
or by any other person or entity, and may not be furnished to, quoted to or by
or relied upon by any other person or entity, without our prior written consent.
We hereby consent to the use of this opinion as an exhibit to the Registration
Statement and to the use of our name under the caption "Material Federal Income
Tax Consequences" in the Joint Proxy Statement. In giving such consent, we do
not thereby admit that we are in the category of persons whose consent is
required under Section 7 of the Securities Act of 1933, as amended, nor do we
thereby admit that we are experts with respect to any part of such Registration
Statement within the meaning of the term "experts" as used in the Securities Act
of 1933, as amended.

                                    Very truly yours,


                                    /s/ WILSON SONSINI GOODRICH & ROSATI 
                                   -------------------------------------
                                    Wilson Sonsini Goodrich & Rosati, 
                                    Professional Corporation



<PAGE>   1
                                                                    EXHIBIT 23.1


                         INDEPENDENT AUDITORS' CONSENT


We consent to the incorporation by reference in this Registration Statement of
Harmonic Inc. on Form S-4MEF of our report dated November 19, 1999 (December 9,
1999 as to Note 1), on the consolidated financial statements of the DiviCom
business (an operating unit of C-Cube Microsystems Inc.) appearing in the Joint
Proxy Statement/Prospectus/Information Statement, which is part of Registration
Statement No. 333-33148 of Harmonic Inc. on Form S-4 dated March 23, 2000. We
also consent to the reference to us under the headings "Consolidated Historical
Financial -- C-Cube/DiviCom" and "Experts" in the Joint Proxy
Statement/Prospectus/Information Statement in such Form S-4.




Deloitte & Touche LLP
San Jose, California
June 2, 2000





<PAGE>   1
                                                                    EXHIBIT 23.2



                       CONSENT OF INDEPENDENT ACCOUNTANTS



We hereby consent to the incorporation by reference in this Registration
Statement on Form S-4 of Harmonic Inc. of our report dated January 18, 2000,
relating to the financial statements appearing in Harmonic Inc.'s Annual Report
on Form 10-KA for the year ended December 31, 1999.

/s/ PricewaterhouseCoopers LLP

PricewaterhouseCoopers LLP
June 1, 2000