A concat playlist only sets the order of your clips; it does not make different codecs compatible. If the videos use different codecs, use FFmpeg’s concat filter to decode, join, and re-encode them. Use the concat demuxer with -c copy only when the input streams are compatible and you want to avoid re-encoding.
Choose the right FFmpeg concatenation method
FFmpeg offers two approaches that sound similar but do different jobs. The concat demuxer reads a text manifest and joins packets; the concat filter joins decoded streams and lets you encode the result. FFmpeg’s FAQ says of the filter: “This operation is recommended if you need to re-encode.” FFmpeg FAQ
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| Approach | Re-encodes? | Input compatibility | Best for |
|---|---|---|---|
Concat demuxer with -c copy |
No | Files need matching streams, including codecs and time bases, and compatible parameters. | Joining compatible clips quickly without another generation of encoding. |
| Concat filter with an encoder | Yes | Different codecs can be decoded and joined, but corresponding streams and other properties may need normalization. | Clips with different codecs or other differences that call for filtering or re-encoding. |
A playlist does not convert one codec into another. Stream copy copies compressed packets without decoding or encoding, so it cannot solve a mixed-codec mismatch. The demuxer also uses each file’s recorded duration to adjust timestamps for the next file; inaccurate durations can cause artifacts. FFmpeg concat demuxer documentation FFmpeg stream-copy documentation
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Inspect the clips before building the output
Check the files’ streams and properties before choosing filters. The example below assumes each clip has one video stream and one audio stream; that assumption does not hold for every file. Inspect codec, resolution, pixel format, frame rate, sample rate, channel layout, and stream presence with ffprobe. Differences in those properties may require normalization even when the clips’ codecs are the same.
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ffprobe -hide_banner -i clip-one.mp4If a clip has no audio, the basic audio-and-video filter graph below cannot select an audio stream from it. Add a silent audio source for that clip or build separate video and audio concatenations. Do not assume that a file extension tells you the codecs or stream layout inside the file.
Create a playlist for compatible clips
For clips that meet the concat demuxer’s compatibility requirements, make a plain-text manifest named, for example, inputs.txt. Put one file entry per line in the order you want them joined:
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file 'clip-one.mp4'
file 'clip-two.mov'
file 'clip-three.mkv'Keep paths relative to the manifest’s directory where practical. The demuxer applies safety checks to paths. The -safe 0 option permits paths that fail those checks, so use it only with a playlist you trust.
Join compatible files without re-encoding using:
ffmpeg -f concat -safe 0 -i inputs.txt -c copy joined.mp4This command is not a solution for different codecs. If FFmpeg reports incompatible streams, or the inputs differ in required stream properties, switch to a filter-and-encode workflow rather than trying to force packet copying.
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Concatenate mixed-codec clips with the concat filter
For two clips that each contain one video and one audio stream, the following is a starting pattern. It decodes the inputs, concatenates the corresponding streams, then encodes an MP4 output using H.264 video and AAC audio:
ffmpeg -i clip-one.mp4 -i clip-two.mov
-filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0]concat=n=2:v=1:a=1[v][a]"
-map "[v]" -map "[a]"
-c:v libx264 -crf 18 -preset medium -pix_fmt yuv420p
-c:a aac -b:a 192k -movflags +faststart output.mp4The filter inputs are ordered video then audio for each clip. concat=n=2:v=1:a=1 tells FFmpeg to join two segments, each with one video and one audio stream. -map selects the resulting filtered streams for output. The video quality setting and preset here are example choices, not universal requirements; encoding choices trade file size, quality, and processing time.
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Normalize mismatched properties when needed
Different codecs are only one possible mismatch. If clips vary in resolution, aspect ratio, pixel format, sample rate, channel layout, or frame timing, add suitable filters before concatenation. Depending on the files, that may include scale, setsar, fps, or aresample. Choose values intentionally after inspecting the inputs; blindly forcing a frame rate or aspect ratio can change the result.
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Prepare the file for YouTube upload
YouTube’s recommended upload settings list MP4, H.264 video, progressive scan, and AAC-LC audio, among other audio options. YouTube recommends uploading at the same frame rate at which the material was recorded. Match the output to the source where practical rather than applying a frame-rate or aspect-ratio conversion without a reason. YouTube recommended upload encoding settings
For SDR uploads, YouTube’s published recommended video bitrates include 8 Mbps for 1080p at standard frame rate and 12 Mbps for 1080p at high frame rate. These are recommendations, not mandatory limits. The page also covers color-space and audio recommendations; check it for the current guidance and details relevant to your footage. Bitrate is not the same thing as a required FFmpeg setting: choose an encoding mode and output characteristics that suit the source and intended upload.
The sample command uses H.264 and AAC in an MP4 container, but its CRF-based video encoding does not target either bitrate figure directly. If you need a particular bitrate, set and verify your encoding parameters deliberately; do not describe the example command as producing a guaranteed bitrate.
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Troubleshoot common concat problems
- The demuxer reports a codec or stream mismatch: The inputs are not suitable for packet-copy concatenation. Use the concat filter and encode, or first make the inputs consistent.
- The output has jumps, gaps, or timestamp artifacts: Check whether input durations are accurate and inspect frame timing. The concat demuxer uses recorded durations to set subsequent timestamps; incorrect duration information can affect transitions.
- The filter graph says a stream cannot be matched or selected: Confirm each input’s stream layout with
ffprobe. The example requires both audio and video in every clip, in the selected stream positions. - Clips differ in size, shape, or audio format: Normalize the relevant video or audio properties with appropriate filters before joining. Pick target settings based on the source rather than assuming one filter value fits all inputs.
- The YouTube upload is rejected or looks wrong: Check the output container, codecs, progressive scan, frame rate, color, and audio against YouTube’s current upload recommendations. Revisit any forced frame-rate or aspect-ratio conversion.
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