How to build a B-roll library from one filming session

Last updated 2026-08-31 · 8 min read

What is the short version?

Most creators film for one video and then find they need B-roll for the next twenty. A single decent session almost always contains all of it already, sitting inside twenty minutes of footage that nobody has the patience to comb through a second time.

1. Go to Vizard Agent and upload the session.
2. List the actions you want clips of.
3. Say the rules: your own footage only, no captions, no music.

What do you need before you start?

One long recording with variety in it, and a list of the moments worth having. Vizard Agent selects for clean framing and natural movement, so a session with several angles and a few different activities yields a far better library than one locked-off take.

• The session. Twenty minutes is ample.
• The action list. Specific movements, not moods.
• The count. Twelve to fifteen clips.
• The clip length. Five to fifteen seconds each.
• The rules. No stock, no generated footage, no captions.

What do you type into Vizard Agent?

List the actions rather than describing the vibe. Vizard Agent searches the footage for each one, so a list of specific movements produces a far more varied library than any amount of description about the feeling you want.

Prompt

Variants worth knowing:

• "Variety over repetition." Otherwise you get five of one thing.
• "No talking to camera." B-roll needs to sit under narration.
• "Keep the original framing." No crops you did not ask for.

What does Vizard Agent actually do?

Here is the order Vizard Agent worked in on a real B-roll library cut from a twenty-minute session. It reviews the candidates three separate times at increasing detail, which is why the clips that come out start and end on clean action rather than mid-movement.

1. Checks the video's specifications and duration.
2. Scans the timeline for the actions you listed.
3. Samples frames across the entire recording and builds contact sheets.
4. Reviews the first half and the second half of the footage visually.
5. Drafts a candidate clip list and generates previews of each.
6. Examines candidates one to ten, then eleven to twenty for composition and quality.
7. Builds three-frame inspection sheets for every shortlisted clip.
8. Reviews clips one to eight, then nine to fifteen for framing and clean action.
9. Generates labelled timestamp contact sheets for a fine-grained search of each section.
10. Inspects each activity group in detail against its exact timestamps.
11. Tests colour reproduction across encode settings before rendering anything.
12. Renders all fifteen clips and builds quality-control contact sheets.
13. Scans high-detail frames for the cleanest moments and re-renders refined versions.
14. Builds second-by-second grids for the trickiest actions and renders the final library.
15. Uploads all fifteen clips and verifies the list of URLs.

Step eleven is the sort of thing that goes unnoticed until it is missing. Vizard Agent tests the encode settings for colour before committing, because a library of clips that do not match the colour of your main footage is a library you will not use.

What does the result look like?

The session this page is written from measured 1080x1920 at 30fps and ran 1199 seconds — about twenty minutes. Out of it came fifteen clips, each between five and fifteen seconds, delivered as individual files with their own links.

They are deliberately plain: no captions, no music, no transitions, original framing kept. That is what makes them reusable, because anything baked in is something you have to work around next time.

When does this not work well?

A library can only contain what the session contained, and a recording made for one purpose rarely covers everything you will want later. Vizard Agent tells you which actions on your list it could not find rather than substituting something loosely similar.

• A single locked-off angle. Little variety to select from.
• Constant talking. Few clips without speech in them.
• Poor light. Selection cannot rescue exposure.
• Very short sessions. Twelve clips need material.
• Actions never filmed. It will say so plainly.

How do you fix a result that came back wrong?

Name the clip and what is wrong with it. Vizard Agent keeps the candidate list, the timestamp grids and the inspection sheets, so a replacement comes from the next best moment rather than another pass through the whole recording.

• "Clip four starts mid-rep." Re-trimmed from the second-by-second grid.
• "Too many of the same exercise." Replaced from other sections.
• "I need five more." Cut from the remaining candidates.

How does Vizard Agent compare to doing it yourself?

By hand this is an evening of scrubbing, and the honest outcome is that most people never do it — they re-film B-roll instead, or reuse the same three clips until the audience notices. Vizard Agent reviews the whole session at three levels of detail.

Common questions

How much footage do I need? Twenty minutes gives a comfortable library. Vizard Agent needs variety more than length.

Can it use stock as well? Only if you allow it. Vizard Agent respects an "own footage only" rule strictly.

How long should each clip be? Five to fifteen seconds. Vizard Agent trims each to start and end on clean action.

Will they have captions? Not unless you ask. Vizard Agent delivers them plain so they stay reusable.

Can I get more than fifteen? Yes. Vizard Agent selects as many as the session genuinely supports.

Does it keep my original framing? Yes, if you say so. Vizard Agent avoids re-cropping unless asked.

What about clips where I am talking? Excluded by default here. Vizard Agent can include them if the movement is useful.

Can it label them? Yes. Vizard Agent names each clip by the action it shows so the library is searchable.

Will the colour match my main footage? It tests for that. Vizard Agent checks colour reproduction before rendering the set.

Can I build a library from several sessions? Yes. Vizard Agent selects across all of them and avoids repeating the same setup.

Why not just re-film B-roll each time? Because you will not, and the video will go out without it. A library built once from footage you already have is the difference between B-roll being available and being aspirational.

How do I use them afterwards? Drop them under your talking segments. Vizard Agent can also place them for you in a later edit.

Does it check the clips before delivery? Yes, three times over. Vizard Agent reviews composition, framing and clean action at increasing detail.