`sections[].laserdisc`¶

Where a section sits on the disc, and the biphase codes it carries. Optional — a section that is not part of a disc structure has no laserdisc: block. A project whose sections have one must also have the top-level laserdisc block.

    laserdisc:
      area: programme_area
      codes:
        - code_type: picture_number
          start_value: 1
        - code_type: chapter_number
          chapter: 1
        - code_type: programme_status
          programme_status: "0x8DC000"

Keys¶

Key	Type	Required	Description
`area`	string	No	The disc area: `lead_in`, `programme_area` or `lead_out`; see `area`
`codes`	list	No	The biphase codes this section carries; see `codes`

The block must set at least one key. An empty block, or any other key, is a parse error.

`area`¶

Marks the section as part of the disc structure.

Value	Meaning	Recommended minimum (CAV)
`lead_in`	Before the programme content	938 frames
`programme_area`	The content itself	—
`lead_out`	After the programme content	1250 frames

A section that carries codes must set it. The minimums are checked as warnings, only on a CAV disc, only for a section that carries codes, and only when duration_frames is an integer:

Laserdisc injection warning: CAV lead_in section has 500 frames; IEC 1.5 mm
minimum at 1.6 um track pitch requires 938.

Ordering rules¶

Once any section is a lead_in or a lead_out, the whole sequence is checked (a project that uses only programme_area is not):

At most one lead_in, and no section may precede it.
At most one lead_out, and no section may follow it.
Every section between them must be programme_area. With only a lead-in this applies to every section after it, and with only a lead-out to every section before it.

Violations are errors, not warnings: out-of-order sections would break monotonic picture-number and time-code generation (IEC 60856/60857).

area also drives the EFM disc-area mapping — a lead-in carries the table of contents, each programme-area section is one EFM track, and the lead-out carries lead-out subcode. That mapping works whether or not the section carries codes, which is why an EFM-only project can have a short lead-in without the 938-frame warning a biphase CAV lead-in would get.

`codes`¶

Key	Type	Applies to	Description
`code_type`	string	All	Which code — see laserdisc code types
`start_value`	int	`picture_number`, `fm_picture_number`	Anchors the count for this section (`fm_picture_number`: first section only)
`chapter`	int	`chapter_number`	Chapter number 0–79
`programme_status`	hex string	`programme_status`	24-bit status word, e.g. `"0x8DC000"`
`users_code`	hex string	`users_code`	24-bit user's code, e.g. `"0x80D234"`

No other key is accepted. code_type is required on every entry, start_value and chapter must be integers, and the hex values must be strings.

Each optional field is read only by the code types listed. A field supplied on another code type is accepted by the parser but ignored. A programme_status or users_code code without its hex value is not written.

No line selection¶

There is no target_lines key. VBI line placement is determined entirely by IEC 60856/60857 from the code type, the disc format, and which field opens the current picture — videosynth computes it per frame. Nor is disc_type repeated here: it is project-wide, in the top-level laserdisc block, and it is required as soon as any section carries codes.

Which codes are legal here¶

The validator checks each code_type against the project's disc_type and this section's area. See the compatibility matrices.

In short:

lead_in:         lead_in, users_code, fm_white_flag (NTSC)
programme_area:  picture_number, picture_stop, chapter_number, programme_status,
                 programme_time_code, clv_code, clv_picture_number,
                 fm_picture_number, fm_programme_time, fm_white_flag (NTSC)
lead_out:        lead_out, users_code, fm_white_flag (NTSC)

Continuity across sections¶

picture_number, programme_time_code and clv_picture_number run continuously across section boundaries by design (IEC 60856/60857 §10.1.5 requires it). The CLV clocks have nothing to configure at all.

For picture_number:

Omit start_value on a section to continue from the previous one. If no earlier section set it, numbering begins at 1.
Set start_value to re-anchor the count at that section — a deliberate discontinuity, for modelling a player skip or a replayed passage.

The same pattern applies to chapter: omit it to continue the previous chapter (carrying its stop-bit track counter across the boundary), set it to start a new one.

Setting start_value: 1 on every chapter would restart the numbering at each boundary, which is almost never what you want.

Examples¶

PAL CAV programme section

    laserdisc:
      area: programme_area
      codes:
        - code_type: picture_number
          start_value: 1
        - code_type: picture_stop
        - code_type: chapter_number
          chapter: 1
        - code_type: programme_status
          programme_status: "0x8DC000"

NTSC CLV programme section — the 40-bit FM codes are mandatory alongside the 24-bit ones

    laserdisc:
      area: programme_area
      codes:
        - code_type: programme_time_code
        - code_type: clv_code
        - code_type: clv_picture_number
        - code_type: chapter_number
          chapter: 1
        - code_type: programme_status
          programme_status: "0x8DC000"
        - code_type: fm_programme_time
        - code_type: fm_white_flag

Lead-in with a user's code

    laserdisc:
      area: lead_in
      codes:
        - code_type: lead_in
        - code_type: users_code
          users_code: "0x80D234"

EFM-only lead-in — no biphase codes, just the disc area

    laserdisc:
      area: lead_in

`vitc` line injections¶

A section's separate line_injections: list carries only vitc, which is not implemented — using it is a validation error:

Project configuration error: line injection type 'vitc' is not implemented in
the current runtime.

A vitc injection still needs a non-empty target_lines, checked first, and cannot share a section with laserdisc codes. A line_injections entry with type: laserdisc is a parse error naming this block:

line_injections[] type 'laserdisc' has moved: laserdisc codes go in the
section's laserdisc.codes list.

sections[].laserdisc¶