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3 line VITC



On Feb 3 David Tosh  dlt at earthlink.net wrote:
>
>The "three line VITC" standard was developed by Aaton & Evertz. This
>would
>be an excellent time for the specifications to be published on the web.
>Listening, Allan, JP?

Yes, I am listening David.  Here is the Evertz version of the standard. 

David also wrote:
>I know that there is a SMPTE group working on a RP for this encoding
>but at
>this point I would rather see documents from the originators available
>now,
>and then we can see if anything changes in the SMPTE RP after it is
>published.

Due to confidentiality of the SMPTE working group document, as committee
members we are not to release these documents while they are in process.
 The document I have posted is what I originally proposed to SMPTE in
the fall of 1994.  In the mean time I have been active in trying to get
the RP through the working group, but the process has been slow.  All I
can say at this time is that there are no substantive changes planned by
SMPTE.

Here is a text version of the 3 line format.  It can be best viewed with
a monospaced font such as courier.  A formatted Microsoft Word document
format more suitable for printing is available from our web page
www.evertz.com.

-----------------------------------------
                                   
        3 Line VITC Encoding Format for Film - Video Transfers
As Generated by Evertz 4025 and Read by Afterburner and AVID Media
Reader
                                   
1.   Overview
-------------

The 3 Line VITC encoding standard specifies a method of encoding video
tape  timecode,  film  edge numbers, and production  timecode  into  3
vertical  interval  timecode  lines.   This  method  of  encoding  the
information  is  intended for use in post production  as  a  means  of
conveying the essential address elements that define the film to  tape
transfer.   The  encoded  data  is  contained  in  a  block  of  three
consecutive  lines  of  the  vertical interval.   There  shall  be  an
optional block of 3 lines for redundancy.  Although the actual  choice
of lines is up to the user, the following line ranges are recommended.

                                 NTSC           PAL
            Block 1              18-19-20       19-20-21
            Block 2(optional)    13-14-15       14-15-16

The  first  line  of the block shall be defined as the  one  occurring
closer  to  vertical sync (i.e. for a block in lines  18-20,  line  18
shall  be  the first line)  The block of VITC lines shall contain  the
following data:

           Time Bits             User Bits                      CRC
Line1      VTR Time              VTR  User Bits                Normal
Line2      KK Prefix, Pulldown   KeyKode Count + Frames        Inverted
Line3      Audio Time            Audio TC User Bits        Nibble
Inverted

The  following sections give the specific details of the  encoding  of
each  line.  The VTR time line shall be encoded with the normal  SMPTE
12M  CRC check word so that existing VITC readers built in to the tape
machines  can  access this information.  Each of the other  two  lines
shall  be  encoded  with their own unique CRC so  that  they  will  be
invisible to existing VITC readers

2.   Video Tape Time (First Line)
---------------------------------
The  video  tape  time is encoded into the first  line  of  the  block
according to the specifications of SMPTE 12M - 1992.  The CRC shall be
the  normal  SMPTE 12M CRC encoding.  The frame rate of this  timecode
will  be 25 frames per second time for PAL systems, and 30 frames  per
second Drop Frame or Non Drop Frame for NTSC systems.

The  User Bits of this line are encoded as 8 hexadecimal digits.   The
content  of the User Bits will be the VTR User Bits for code generated
by  the  Evertz 4025, or video tape reel number, or any arbitrary  HEX
values.


3.   KeyKode (Second Line)
--------------------------

The  KeyKode information and pulldown flags shall be encoded into  the
second  line of the block.  The CRC shall be the inverse of the  SMPTE
12 CRC.

The  Time  Bits  of  the KeyKode line are used to store  the  pulldown
flags,  film manufacturer film gauge, emulsion type, and part  of  the
prefix  digits of the KeyKode number.  The chart below shows  how  the
time Bits are encoded.  Film manufacturer and type id is encoded as  a
HEX  nibble.  Film emulsion, prefix and footage are encoded as  packed
BCD digits.  Frame count is encoded as a binary number.  The remainder
of the information is bit map encoded as shown in Table 1 to Table 5.

Timecode Nibble      VITC Bit #   Contents

Hours Tens           75           Field Flag 0=Fld 1, 1=Fld 2
                     72-74        Pulldown flags (See Table 2 to Table
5)
Hours Units          62-65        Film Mfg. and type ID (See Table 1)
Minutes Tens         52-55        Film Emulsion Type 1 (MS Digit)
Minutes Units        42-45        Film Emulsion Type 1 (LS Digit)
Seconds Tens         32-35        Prefix 1 (MS Digit)
Seconds units        22-25        Prefix 2
Frames Tens          12-15        Prefix 3
Frames Units         02-05        Prefix 4

Note 1 The  film  emulsion type corresponds to the encoded  values
       recovered  from the machine readable barcode, and not the  letter
       codes on the human readable part of the edge number.

The  User Bits of the KeyKode line contain the rest of the prefix, the
counting  part of the KeyKode number, (sometimes referred  to  as  the
footage),  the  frame  offset from the last KeyKode  number,  and  the
maximum frame count.  Encoding for the User Bits is as follows:

User Bit Nibble      VITC Bit #   Contents

Group 8 (Hrs tens)   76-79        Prefix 5
Group 7 (Hrs units)  66-69        Prefix 6 (LS Digit)
Group 6 (Min tens)   56-59        Footage 1 (MS Digit )
Group 5 (Min units)  46-49        Footage 2
Group 4 (Sec tens)   36-39        Footage 3
Group 3 (Sec units)  26-29        Footage 4(LS Digit )
Group 2 (Frm tens)   18-19        Maximum Frame Count
                     16-17        Frames 2 MSB
Group 1 (Frm Units)  06-09        Frames 4 LSB

The frame number is encoded in binary in the least significant byte of
the  User  Bits data along with two flags which identify  the  maximum
frame count for that key number.

The  Maximum  frame  count is encoded as two bits and  is  interpreted
differently  based on the film manufacture ID nibble (bits  62-65)  as
shown in Table 1 below.

Mfg.   Film Mfg.   Format        Max. Frame Count        Bit    Bit
ID                                                        18    19
0      Ink         35 mm (4perf) 16                       0      0
                   16 mm         20                       0      1
                   16 mm         40                       1      0
                                 reserved                 1      1
1      Agfa        35 mm         16 (4 perf - KK /ft& fr  0      0
2      Kodak                     21 (3 perf head dot p1   0      1
3      Fuji                      21 (3 perf center dot p2 1      0
                                 22 (3 perf tail dot p3   1      1
4      Agfa        65/70 mm      24 (5 perf)              0      0
5      Kodak       (120 perf/key 15 (8 perf)              0      1
6      Fuji        Number cycle) 12 (10 perf)             1      0
                                 8 (15 perf)              1      1
7      Agfa        65/70 mm      16 (5 perf)              0      0
8      Kodak       (80 perf/Key  10 (8 perf)              0      1
9      Fuji        Number cycle) 8 (10 perf)              1      0
                                 reserved                 1      1
A      not used                                                  
B      Agfa        16 mm         reserved                 0      0
C      Kodak                     20 (Key # & frames)      0      1
D      Fuji                      40 (Foot & frames)       1      0
                                 reserved                 1      1
E      not used                                                  
F      not used                                                  

                 Table 1: Film Types and Frame Counts


3.1  Pulldown Flags
-------------------

Three pulldown flags  (encoded as bits 72-74) uniquely identify any of
the  video frames that can result from the pulldown sequence.   Notice
that the flags do NOT change in the middle of a video frame.

       Bit
       72, 74    Used to uniquely identify the pulldown sequence.
       73        0 = video frame containing the same film image in both
                     fields
                 1 = video frame containing different film images in
each
                     field
       75        0 = video field 1
                 1 = video field 2

Film Frame  Video Fld   PD 3      PD 2      PD 1    Nibble   Video Frm
             Bit 75    Bit 74    Bit 73    Bit 72   Value    Example
    A          0         1         0         0        4       0:00
               1         1         0         0        C         
    B          0         1         0         1        5       0:01
               1         1         0         1        D         
               0         0         1         1        3       0:02
    C          1         0         1         1        B         
               0         0         1         0        2       0:03
    D          1         0         1         0        A         
               0         0         0         0        0       0:04
               1         0         0         0        8         
    A          0         1         0         0        4       0:05
               1         1         0         0        C         

                  Table 2: NTSC 24 FPS Pulldown Flags


Film Frame  Video Fld   PD 3      PD 2      PD 1    Nibble   Video Frm
             Bit 75    Bit 74    Bit 73    Bit 72   Value    Example
    A          0         1         0         0        4       0:01
               1         1         0         0        C         
    A          0         1         0         0        4       0:02
               1         1         0         0        C         

  Table 3: NTSC 30 FPS and PAL 25 FPS Field 1 Dominant Pulldown Flags


Film Frame  Video Fld   PD 3      PD 2      PD 1    Nibble   Video Frm
             Bit 75    Bit 74    Bit 73    Bit 72   Value    Example
    C6         0         1         1         0        6       0:01
    C7         1         1         1         0        E         
               0         1         1         0        6       0:02
    C8         1         1         1         0        E         

  Table 4: NTSC 30 FPS and PAL 25 FPS Field 2 Dominant Pulldown Flags


Film Frame  Video Fld   PD 3      PD 2      PD 1    Nibble   Video Frm
             Bit 75    Bit 74    Bit 73    Bit 72   Value    Example
    A1         0         1         0         0        4       0:00
               1         1         0         0        C         
    A2         0         1         0         0        4       0:01
               1         1         0         0        C         
    A3         0         1         0         0        4       0:02
               1         1         0         0        C         
    A4         0         1         0         0        4       0:03
               1         1         0         0        C         
    A5         0         1         0         0        4       0:04
               1         1         0         0        C         
    A6         0         1         0         0        4       0:05
               1         1         0         0        C         
    A7         0         1         0         0        4       0:06
               1         1         0         0        C         
    A8         0         1         0         0        4       0:07
               1         1         0         0        C         
    A9         0         1         0         0        4       0:08
               1         1         0         0        C         
   A10         0         1         0         0        4       0:09
               1         1         0         0        C         
   A11         0         1         0         0        4       0:10
               1         1         0         0        C         
    B1         0         1         0         1        5       0:11
               1         1         0         1        D         
               0         0         1         1        3       0:12
    C1         1         0         1         1        B         
               0         1         1         0        6       0:13
    C2         1         1         1         0        E         
               0         1         1         0        6       0:14
    C3         1         1         1         0        E         
               0         1         1         0        6       0:15
    C4         1         1         1         0        E         
               0         1         1         0        6       0:16
    C5         1         1         1         0        E         
               0         1         1         0        6       0:17
    C6         1         1         1         0        E         
               0         1         1         0        6       0:18
    C7         1         1         1         0        E         
               0         1         1         0        6       0:19
    C8         1         1         1         0        E         
               0         1         1         0        6       0:20
    C9         1         1         1         0        E         
               0         1         1         0        6       0:21
   C10         1         1         1         0        E         
               0         1         1         0        6       0:22
   C11         1         1         1         0        E         
               0         0         1         0        2       0:23
    D1         1         0         1         0        A         
               0         0         0         0        0       0:24
               1         0         0         0        8         
    A1         0         1         0         0        4       1:00
               1         1         0         0        C         
                  Table 5: PAL 24 FPS Pulldown Flags


3.2  Example
------------

For a sample 35 mm (4 perf) KeyKode number     KJ12 3456 7890+12

Manufacturer's Code   02   Letter code K for Kodak is encoded as 02 for
35 mm
Film Type             96   Film type 5296 has letter code J
Prefix                123456
Footage               7890
Frames                C    Binary representation of 12 frames
Field & Pulldown      4    A Frame Pulldown & Field 1

This  KeyKode word will be encoded as follows assuming the first video
field of an A frame:

TIME BITS             USER BITS
HH MM  SS  FF         12  34  56 78
42 96  12  34         56  78  90 0C


4.   Production Time Code (Third Line)
--------------------------------------

The  Production time code shall be encoded into the third line of  the
block  according to the specifications of SMPTE 12M - 1992.   The  CRC
shall  be calculated in the same way as the normal SMPTE 12M CRC,  but
will have the high order nibble inverted.

The  time bits of the Production time code line shall contain the  In-
Camera  or  Audio  time and frame count.  The default  frame  rate  of
Production time code will be 25 fps for PAL systems, and 30  fps  Drop
Frame  or Non Drop Frame for NTSC systems.  The frame rate is  encoded
into VITC bit 74 & 75 (in the hours tens) as follows:

Bit 74 Bit 75  Frame Rate
  0       0    24 (Future)
  0       1    25
  1       0    30 (29.97)
  1       1    other (manually set up on reader)

The  user  bits  will normally contain  the User  Bits  of  the  audio
timecode  or  in camera timecode.  Two flag bits are used to  indicate
the format of the user bit encoding as follows:

Bit 55 Bit 35  User Bit Encoding Format
  0       0    not encoded (8 Hexadecimal digits)
  0       1    encoded according to date/camera ID format (see below)
  1       0    reserved
  1       1    reserved

The date/Camera ID format of the user bits is defined as follows:

The year (00-99) is encoded into 7 bits
The month (01 to 12) is encoded into 4 bits
The day (01 to 31) is encoded into 5 bits
Each camera ID digit is a hexadecimal digit containing values 0 to  F.
The full camera ID is 4 hex digits.

User Bit Nibble      VITC Bit #   Contents
User Bit Nibble  VITC Bit #   Contents

Group 8 (Hrs tens)   76-79        Year 4 MS bits
Group 7 (Hrs units)  67-69        Year 3 LSB
                     66           Month MSB
Group 6 (Min tens)   57-59        Month 3 LSB
                     56           Day MSB
Group 5 (Min units)  46-49        Day 4 LSB
Group 4 (Sec tens)   36-39        Camera ID 1 (MS digit)
Group 3 (Sec units)  26-29        Camera ID 2
Group 2 (Frm tens)   16-19        Camera ID 3
Group 1 (Frm Units)  06-09        Camera ID 4 (LS digit)


>--------------------------- Alan Lambshead:  - V.P., Director of
>Engineering:   E-mail:  alan at evertz.com --------
>--------------------------- Evertz Microsystems Burlington, Ontario,
>Canada ------http://www.evertz.com -------- 
>--------------------------- Phone: 905-335-3700   Fax: 905-335-3573  
>BBS: 905-335-9131-------------------------
>
>
>
>

--------------------------- Alan Lambshead:  - V.P., Director of
Engineering:   E-mail:  alan at evertz.com --------
--------------------------- Evertz Microsystems Burlington, Ontario,
Canada ------http://www.evertz.com -------- 
--------------------------- Phone: 905-335-3700   Fax: 905-335-3573  
BBS: 905-335-9131-------------------------