Other than a few non-standard exceptions, all interlaced video formats are field 1 dominant. This means that for a given frame, field 1 (F1) is recorded earlier in time, and therefore should be displayed first during broadcast. Field 2 (F2) is recorded after F1 and is therefore displayed after F1 during broadcast.

Where interlaced video formats differ, however, is in the first active line. The first active line is the uppermost line in the frame: in some interlaced video formats, this uppermost line belongs to F1; in others, it belongs to F2.

With mixed-resolution projects, you can mix interlaced video formats that have different first active line properties. However, you must account for the differences between the two formats. Otherwise, you risk outputting a result that displays one of the interlaced video formats improperly—introducing noticeable jitter as the field that was recorded earlier in time is displayed after the field that was recorded later in time.

You can mix clips with differing interlaced video formats in a project by reversing the field dominance of clips that do not correspond with your project's default resolution interlacing properties. For example, if you bring a PAL clip into an NTSC project whose material is F2 dominant, you should reverse the field dominance of the PAL clip.

When working with clips that have conflicting field dominance, you can:

• Change the scan mode of the project for the current session. Use this procedure to preview material with incorrect field dominance.
• Reverse the field dominance of a clip so it matches the rest of your material. Use this procedure, for example, to allow an F1 PAL clip to mix properly with an F2 NTSC clip.

All clips in Backdraft Conform have a metadata tag for scan mode. This tag is assigned when the material is first brought in. If the tag scan mode is incorrect, you can change it to match the actual scan mode of the clip.