To play several local video files back to back with FFmpeg, put them in a text file in playback order and use the concat demuxer. If their streams are compatible, -c copy joins them without re-encoding. That creates a continuous media sequence; publishing it as a live stream is a separate step that depends on the destination’s ingest requirements.
Choose the right kind of FFmpeg concat
FFmpeg has three concat mechanisms. Pick one based on how the files are encoded and what you need to do with them:
| Need | Method | Main constraint |
|---|---|---|
| Join similarly encoded files without re-encoding | Concat demuxer | Inputs need matching streams, codecs and time bases; duration metadata affects timestamps. |
| Inputs differ and need normalization | Concat filter | Requires decoding and encoding with chosen output settings. |
| Join resources at the file level | Concat protocol | Only suitable for formats that support this kind of concatenation. |
The concat demuxer is generally the best starting point when the files are already encoded alike and you want to avoid generation loss. FFmpeg’s FAQ explains when to use the concat demuxer, filter and protocol.
Make a concat list and join compatible files
1. Create the list in playback order
In the directory containing the files, create a plain-text file named list.ffconcat:
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ffconcat version 1.0
file 'first.mp4'
file 'second.mp4'
file 'third.mp4'The header must be the exact first line for automatic format recognition: no byte-order mark and no extra spaces. Add one file directive per input, in the order you want it played. Quote or escape paths containing spaces or special characters. The demuxer may reject absolute paths and protocols under its safe-path checks; use relative paths where practical. The concat demuxer documentation describes the script syntax and safe-path behavior.
2. Check that the streams are compatible
Before using stream copy, compare the files’ stream layout, codecs, dimensions, frame rates and time bases, audio streams, and relevant stream parameters. The demuxer expects the same streams in each file; matching file extensions alone do not establish compatibility. FFmpeg’s documentation states that files must have the same streams, including codecs and time base. -c copy cannot fix differences because it copies encoded packets without decoding, filtering or encoding.
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3. Run the stream-copy command
ffmpeg -f concat -i list.ffconcat -c copy output.mp4This writes a local MP4 output. Stream copy is fast and avoids re-encoding, but it works only when the input streams are compatible with one another and the chosen output container. The FFmpeg command-line manual explains stream copy and option behavior.
If the list needs paths outside the demuxer’s safe relative-path subset, and all listed inputs are trusted, you can deliberately disable that check:
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ffmpeg -f concat -safe 0 -i list.ffconcat -c copy output.mp4Do not add -safe 0 routinely for ordinary relative filenames.
When inputs differ: normalize with the concat filter
If the files have different streams or parameters, stream copy will not normalize them. Use a filter workflow that decodes the inputs, brings them to compatible formats, concatenates them, then encodes the result. FFmpeg’s FAQ recommends the concat filter when re-encoding or normalization is needed. The exact filter graph and encoding settings depend on the inputs and desired output, so there is no single safe command that fits every mismatched set. First establish a common video and audio format, dimensions, frame rate and channel layout, then configure the filter graph and output encoder accordingly.
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Understand ordering, timestamps and gaps
The list determines playback order; FFmpeg does not automatically discover new files or append files that arrive after processing starts. The demuxer starts the first file at timestamp zero and offsets later files based on the preceding file’s duration. If a duration is missing or inaccurate—for example, because a file is truncated or its duration is estimated poorly—the next segment can start at the wrong timestamp and produce gaps or artifacts. A duration directive in the list can override an inaccurate or missing duration; consult the demuxer documentation for its syntax.
A static concat list is not an endless playlist manager or a documented hot-reload mechanism. If files are added dynamically or you need a never-ending schedule, you need a separate process or scheduling design rather than assuming edits to the list will be picked up while FFmpeg is running.
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Concat protocol: a narrower alternative
The concat protocol reads resources sequentially as one resource, using syntax such as concat:URL1|URL2. It is intended for formats that support file-level concatenation, such as MPEG program streams, not as a universal way to join arbitrary MP4 or other containers. The pipe character may need shell escaping. FFmpeg’s protocol documentation gives an escaped ffplay example, and its FAQ shows a concatenation example for MPEG intermediates.
Publish the sequence as a live stream
Concatenation chooses and timestamps the input media; it does not determine how to deliver it to a live destination. To publish, keep the concat input and replace output.mp4 with an output format, protocol and destination supported by the receiving service. Select codecs, transport settings and credentials using that service’s current official ingest instructions. Because the destination is unspecified here, there is no universal RTMP, HLS or other live-output command to recommend.
For a DIY process that must remain online, the computer or server running FFmpeg and its network connection must remain available, and you must handle process restarts and changing playlists yourself. A VPS is optional infrastructure, not a requirement for concatenating files.
Troubleshooting common concat problems
- FFmpeg rejects the list format: Check that
ffconcat version 1.0is the exact first line, with no byte-order mark or leading spaces, and that each file directive is spelled and quoted correctly. - A path is rejected as unsafe: Use relative paths within the safe subset, or add
-safe 0only when the list contains trusted paths that require it. - Stream copy fails or the output behaves incorrectly: Compare the inputs’ streams, codecs, time bases and parameters. Use a normalization and re-encoding workflow with the concat filter if they differ.
- There is a gap, timestamp jump or artifact at a boundary: Check that files are complete and that their durations are accurate. A duration directive may correct missing or inaccurate duration metadata.
- The live output does not connect: Concat is only the media input. Verify the destination’s current supported protocol, codecs, transport and stream credentials separately.
- New files do not appear in the sequence: A static list does not automatically incorporate files added later. Use a separate scheduling or process-management design for a changing or endless playlist.
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