CampaignReel

Ad placement specs against what generators output

Which entries name the value a field falls back to

An unset parameter is still a parameter. Four entries name the shape a request falls back to: three say sixteen by nine and one says adaptive, which hands the decision to the model. Every published default here is horizontal or model-chosen. As of 2026-09-22.

Every published default is horizontalThree entries fall back to sixteen by nine and one to adaptive. Feed and vertical placements are the common case in advertising, and none of the defaults points at them.The MastheadA feed or vertical surfaceShape requiredWidescreenVerticalOn a page that defaults to 16:9Arrives without askingThe field must be setOn the page that defaults toadaptiveUnknown in advanceUnknown in advanceThe rest of this column has no documented fallback
Fig. 1 So the common case has to be asked for on every row, and the rare one arrives free.
What each entry says happens when the shape field is left alone. Recorded 2026-09-22.
ItemWhat is publishedDetail
16:9 as the defaultThree entriesMatches the Masthead and no feed surface
adaptive as the defaultOne entryThe model chooses, so the output shape is unknown in advance
No default statedThe remaining entriesAn omitted field has no documented behaviour

Inclusion rule. Entries whose own page names a fallback value for the aspect ratio field. A value described as typical rather than as a default is not counted. Order. The most common default first.

1A default is a specification, not a detail

Where the fallback is published, a pipeline that forgets the field produces something checkable. Where it is not, the output is whatever the vendor chose and nothing on the page predicts it, which is the position most of this column is in.

Two entries publish identical lists of six shapes and behave differently for exactly this reason: one defaults to adaptive and the other requires the field. The list is the same and the production risk is not.

2Every published default points at the wrong surface

Sixteen by nine matches the Masthead, which is the one format in this register that states a shape. Feed and short-form placements are vertical, and they are where most generated advertising runs.

So the common case has to be asked for on every row and the rare case arrives free. That is a fact about how these products were built rather than about where the ads go, and it is worth knowing before a batch runs unattended.

3Adaptive is the one default a placement cannot accept

Every surface here accepts specific shapes. A file whose shape was chosen by the model is a file whose acceptance was chosen by the model, and a batch generated without the field set can come back in several shapes across one campaign.

Nothing errors, the pieces look correct on their own, and the problem appears at upload. The fix is one line in every request, and it has to be deliberate precisely because nothing fails loudly.

4From brief to placement

For ad work around “Published defaults”, SceneMixer's pages explain how its ad projects are produced:

16:9 landscape (SceneMixer's default) and 9:16 vertical (the usual short-drama frame), chosen per project.

SceneMixer, Seedance 2.0 in a Real Short-Drama Pipeline — “Which aspect ratios does the pipeline generate?” (read 2026-10-13)

The spoken lines and the end card follow your interface language across fifteen dialogue languages, with the cast and setting adapted to that market. The end card falls back to a language it can typeset when a script needs shaping or right-to-left layout.

SceneMixer, AI Ad Video Generator — “Which languages can the ad be in?” (read 2026-10-13)

5Sources

Format requirements come from Google Ads Help, read 2026-09-12, and tool limits from each vendor page listed on published limits, read 2026-09-22. The rule against mixing the two is on method. Nearby: A minute in one call, Ceilings on inputs, Sound that arrives.