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FFmpeg does not have a concat-demuxer setting for shuffling files or enforcing an episode cooldown. Shuffle the episode list before FFmpeg reads it, then write that order to a concat playlist. A shuffled pass plays each listed file once; if you loop the playlist, check its first and last entries to avoid an immediate repeat at the boundary.
How shuffling works with FFmpeg
The concat demuxer reads file entries in the order they appear; it does not randomize them. The practical method is to generate a randomized list outside FFmpeg and pass that list to the demuxer. Python’s random.shuffle changes a list in place, while random.sample can return a selection without replacement. See the FFmpeg concat documentation and Python 3.11 random documentation.
Create a shuffled playlist
1. Prepare the episode files
Put the videos in a dedicated videos directory beside the script below. This example looks for MP4 files and assumes portable filenames without spaces or special characters. It requires at least two files.
2. Generate the concat script
Save this as a Python script in the directory containing videos, then run it. It writes one file directive per episode in randomized order. The loop that compares the first and last entries prevents the last video of a pass from being immediately followed by the first video when the same playlist loops.
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from pathlib import Path
import random
files = sorted(Path("videos").glob("*.mp4"))
if len(files) < 2:
raise SystemExit("Put at least two episode files in videos/")
random.shuffle(files)
# Avoid an immediate repeat at the loop boundary.
while files[-1] == files[0]:
random.shuffle(files)
with open("playlist.ffconcat", "w", encoding="ascii") as playlist:
playlist.write("ffconcat version 1.0n")
for path in files:
playlist.write(f"file {path.as_posix()}n")The shuffle is random rather than a guarantee that episodes will be evenly spaced. With two files, for example, one must follow the other within every pass. The first/last check only addresses the transition between the end and start of the playlist.
3. Concatenate one shuffled pass
Run this from the same directory as playlist.ffconcat:
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ffmpeg -f concat -safe 1 -i playlist.ffconcat -c copy shuffled.mp4-c copy attempts stream copying rather than re-encoding. It is suitable only when the inputs meet the concat demuxer’s compatibility requirements, including matching streams, codecs, and time bases. If they do not, use a compatible normalization or filter-based concat workflow that re-encodes as needed; the FFmpeg FAQ explains the distinction between concat-demuxer and concat-filter approaches.
4. Loop the ordered playlist indefinitely
To loop the playlist as an input while producing an output file or stream, put -stream_loop -1 before the input:
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ffmpeg -stream_loop -1 -f concat -safe 1 -i playlist.ffconcat -c copy output.mp4FFmpeg documents -1 as infinite looping and 0 as no loop. Because the playlist is unchanged, each pass repeats the same sequence. The option loops the input; it does not generate a fresh shuffle for each pass. See the FFmpeg main options.
Choose the repeat protection you need
No repeat within one pass
A shuffle without replacement puts each listed file into the generated pass once. It prevents a file from appearing twice in that pass, but after all files play, a loop starts the same sequence again.
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No immediate repeat across the loop boundary
The first/last check in the example prevents the final entry from matching the first entry. It does not prevent an episode from returning after one or more other episodes, nor does it change the order on later passes.
A longer cooldown across passes
To enforce a rule such as “do not replay an episode until several other episodes have played,” use a scheduler that remembers recent episode identities and chooses only an eligible episode outside that recent-history window. The library must contain enough distinct episodes to meet the cooldown. If two files are alternate encodes or duplicate copies of the same episode, treat them as one episode identity; a filename-based shuffle cannot infer that they tell the same story.
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Paths, compatibility, and output caveats
Safe paths and special characters
The example uses -safe 1, which accepts relative paths made from portable characters and rejects unsafe path forms. FFmpeg documents -safe 0 as permitting any filename, but do not switch to it casually; use it only for trusted local paths when necessary. Spaces and special characters in concat-script paths require FFmpeg’s concat-script quoting or escaping rules. Shell quoting alone does not necessarily make a path valid inside the script. Refer to the concat documentation for its path rules and examples.
Matching input streams and timestamps
The concat demuxer expects files to have the same streams, codecs, and time bases. The FFmpeg manual also warns that inaccurate file durations can cause timestamp artifacts because durations help position subsequent files. If inputs differ, normalize them or use a filter-based concat workflow with re-encoding as appropriate rather than assuming stream copy will work.
Documentation for your installed build
The online FFmpeg documentation is regenerated nightly and corresponds to the newest revision. If your installed FFmpeg is older, consult the documentation shipped with that build; the project’s documentation index makes this distinction.
Troubleshooting
- The episodes play in the same order every time: the concat demuxer follows the playlist exactly. Regenerate
playlist.ffconcatwith a new shuffle before starting another pass if you want a new order. - The same episode starts immediately after itself at the loop point: confirm the generated playlist’s first and last entries differ. The boundary check does not provide a longer cooldown.
- FFmpeg rejects a path: keep filenames and entries within the
-safe 1rules, or apply the concat-script escaping rules for the actual path. Use-safe 0only when the playlist points to trusted local files. - Stream copy fails or the join has glitches: inspect whether the files have matching streams, codecs, and time bases, and whether their durations are accurate. Normalize incompatible inputs or use a filter-based concat workflow that re-encodes as necessary.
- Two files containing the same episode appear far apart: the script shuffles file paths, not episode content. Deduplicate or group alternate copies by episode identity before scheduling.
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