Generate the countdown or holding screen as its own video segment, then place it between your clips. For unlike files—or whenever you need to normalize video and audio—use FFmpeg’s concat filter and re-encode. The concat demuxer can avoid re-encoding only when the files, including the slate, have matching streams and compatible timing.
Choose the right way to join the slate and videos
A countdown is changing text rendered over video; a holding screen is a video segment, often made from a solid color or a still image. In either case, give the interstitial an explicit duration and insert it between the video segments.
| Approach | Use it when | Important constraint |
|---|---|---|
| Concat filter | Inputs need normalization, have different formats, or must be re-encoded together. | Decode and encode the segments. Build a filtergraph for every segment and include audio if you need a continuous audio stream. The FFmpeg FAQ recommends this approach when re-encoding is needed. |
| Concat demuxer | Files already have matching streams and you want to avoid re-encoding. | Files must have the same streams, codecs, and time bases. The demuxer uses file durations to place later segments, so inaccurate duration metadata can cause timestamp artifacts or gaps. See the FFmpeg Formats Documentation. |
Do not assume that adding -c copy makes arbitrary MP4s join cleanly. FFmpeg distinguishes the concat filter, demuxer, and protocol because each has different constraints; consult the official concat FAQ before choosing.
Generate a countdown slate
This illustrative command creates a ten-second, 1920Ă—1080, 30 fps black slate with centered countdown text. Replace the font path with a font file present on your host and adapt the dimensions, frame rate, duration, and output encoding to your stream.
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ffmpeg -f lavfi -i "color=c=black:s=1920x1080:r=30:d=10"
-vf "drawtext=fontfile=/path/to/font.ttf:text='Next video in %{eif\:max(0\,10-t)\:d}':fontsize=64:fontcolor=white:x=(w-text_w)/2:y=(h-text_h)/2"
-t 10 slate.mp4The command is an example, not a verified cross-platform recipe: escaping may need adjustment for your shell, operating system, and FFmpeg build. The expression uses elapsed time in the slate rather than a wall clock. Decide whether the first displayed value should be 10 or 9, how fractional frames round, and whether zero should remain visible for a full second.
Check drawtext support
The drawtext filter depends on FFmpeg being built with libfreetype; available font-selection support can also vary with build options. Check your installed build and use an existing font file for reproducible results. The FFmpeg Filters Documentation describes drawtext, centered positioning, and expression features.
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Make a holding screen from color or an image
A solid background can come from FFmpeg’s color source. For a branded slate, use a still image as the video or composite a logo over a generated background with overlay. If the image is a separate input, make sure it lasts for the whole slate interval and that its timestamps align with the video. The overlay documentation notes that inputs are consumed in timestamp order; resetting offset initial timestamps with setpts=PTS-STARTPTS may be appropriate. See the filters documentation for color, overlay, and loop.
The loop video filter can repeat a chosen number of frames, including indefinitely, but it does not decide how long the complete output should run. Set a deliberate duration or stop condition for the slate.
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Insert the slate between clips
Use the concat filter for a normalized render
For clips that differ in size, frame rate, pixel format, audio sample rate, or channel layout, decode and normalize them before concatenation. Add the generated slate as another segment in the same filtergraph. A concat-filter graph must account for each input segment; map the resulting video and, if needed, audio streams explicitly. The exact graph and encoding options depend on the media files and intended output, so there is no safe universal command that fits arbitrary clips.
Use -filter_complex for a complex graph and explicit -map options to select the intended outputs. Confirm the target’s video codec, pixel format, frame rate, audio codec, and muxer requirements. The FFmpeg documentation covers complex filtergraphs and stream mapping.
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Use the concat demuxer only for matching files
Create a text playlist in the intended sequence—outgoing clip, slate, next clip—and pass it to the concat demuxer. This approach is suitable only if the files have matching streams, codecs, and time bases. Make the slate’s codecs and stream layout match the neighboring files, and inspect file durations: the demuxer uses duration information to position subsequent files, so incorrect metadata can introduce gaps or timestamp artifacts.
Plan audio and timing before streaming
- Choose an audio policy. If the output should carry audio continuously, provide matching audio for the slate, such as silence, or build a filtergraph that maintains a continuous audio stream. A slate without audio can create a gap or a stream-layout mismatch when joined to clips that have audio.
- Keep timestamps deliberate. Align segment timestamps, especially when compositing a separate image or joining files with the demuxer. Check the resulting transition rather than assuming durations and timestamps are correct.
- Set output requirements explicitly. Match video and audio codecs, pixel format, frame rate, sample rate, channel layout, and muxer to the destination; use explicit stream mapping where appropriate.
- Decide whether the job is finite or persistent. Rendering a finite playlist to an RTMP, HLS, or DASH destination is a different problem from keeping a connection open indefinitely while waiting for new clips. Queueing, reconnect behavior, and scheduling depend on the output protocol and deployment; FFmpeg’s concat features alone do not define a universal live queue.
Troubleshoot common failures
- “No such filter: drawtext” or a related filter error: the installed build may not include the required libfreetype support. Check the build’s available filters and use a build that includes the dependency.
- Font cannot be found or text does not render: replace the example path with a font file that exists on the host. A font name alone may rely on fontconfig support that your build does not have.
- Countdown text updates unexpectedly: the expression is based on local elapsed time and frame timing. Verify the intended start value, rounding behavior, and whether zero should appear; also check escaping for your shell and filtergraph.
- Concat demuxer reports mismatches or the transition glitches: compare stream layouts, codecs, time bases, and duration metadata for every file, including the slate. If they differ, use a normalized re-encode with the concat filter instead.
- Audio disappears, gaps, or fails to join: check whether every segment has compatible audio streams. Add silence or otherwise construct continuous audio, and ensure the selected concat method and output muxer support the resulting layout.
- A still-image slate ends too soon or begins at the wrong time: ensure the image input covers the full interval and align timestamps. Reset offset initial timestamps where needed, as described in the overlay documentation.
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FFmpeg’s official documentation is rolling and the cited pages do not establish a single release number. Commands above are illustrative; a production-ready live command depends on your FFmpeg build, media, audio policy, protocol, and scheduling model.
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