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FFmpeg does not have a concat-demuxer setting to shuffle files or enforce an episode cooldown. Shuffle the episode list before FFmpeg reads it, then use the concat demuxer to play that order. This guarantees each listed file appears once per pass; avoiding repeats over several passes requires a scheduler that remembers recent episodes.
How FFmpeg handles a shuffled playlist
The concat demuxer reads a text file of media entries in the order they are listed; it does not choose or randomize them. The practical division of work is simple: use a script to make the order, then give that playlist to FFmpeg. See the FFmpeg concat documentation.
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A shuffle without replacement means each file appears once in a pass. If you loop that playlist, the same ordered pass starts again. You can prevent the last episode in one pass from being immediately followed by the first episode in the next, but that alone is not a multi-episode cooldown.
Create a shuffled concat playlist
1. Prepare the episode files
Put the episode videos in a folder named videos alongside the script below. This example looks for files ending in .mp4 and assumes portable filenames without spaces or special characters. It requires at least two files so it can avoid a same-file repeat at the loop boundary.
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2. Shuffle once and write the playlist
Python’s random.shuffle shuffles a list in place. The code writes the resulting order to a concat script and reshuffles if the first and last entries match:
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)
# If the playlist will loop, avoid an immediate repeat at the 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 Python 3.11 documentation describes random.shuffle as modifying the sequence in place; random.sample(files, k=len(files)) is another way to produce a selection without replacement. See the Python random documentation.
Each file directive tells the concat demuxer which path to read next. The first line identifies the script as an ffconcat file. This example’s simple path assumptions are deliberate; paths with whitespace or special characters need concat-script quoting or escaping, as described in the FFmpeg documentation.
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Run the playlist once or loop it
Make one output file
From the directory containing playlist.ffconcat, run:
ffmpeg -f concat -safe 1 -i playlist.ffconcat -c copy shuffled.mp4-c copy asks FFmpeg to copy the streams instead of re-encoding. It is suitable only when the inputs meet the concat demuxer’s compatibility requirements. If they do not, use a filter-based concat workflow and re-encode as needed.
Repeat the playlist indefinitely
To loop the entire ordered playlist as an input, put -stream_loop -1 before the input options:
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ffmpeg -stream_loop -1 -f concat -safe 1 -i playlist.ffconcat -c copy output.mp4FFmpeg documents -1 as infinite input looping and 0 as no looping. The concat demuxer still follows the same list on every pass, so this command repeats the same order rather than generating a fresh shuffle. See the FFmpeg main options.
Choose the repeat guarantee you need
| Approach | What it guarantees | What it does not guarantee |
|---|---|---|
| Shuffle without replacement | Each listed file appears once during that playlist pass. | No particular spacing between episodes once the list is played again. |
| Check first and last entries | A different file starts the next pass, if the playlist has at least two distinct entries. | A cooldown of several episodes across passes. |
| Persistent recent-history scheduler | Can exclude episode identities played within a chosen recent-history window. | It cannot satisfy a cooldown longer than the available pool of distinct episode identities allows. |
For a true multi-episode cooldown, have an external scheduler record recent episode identities, choose only an eligible episode, and update that history as playback advances. The library must contain enough distinct episodes to meet the cooldown. If two files are alternate encodes or duplicate copies of the same story, treat them as one episode identity; a file-level shuffle cannot detect that relationship on its own.
Check compatibility, paths, and durations
- Matching media streams: The concat demuxer expects files to have the same streams, codecs, and time bases. When they differ, normalize the sources or use the concat filter and re-encode as appropriate. The FFmpeg FAQ explains the distinction between demuxer concatenation and filter-based concatenation.
- Safe paths:
-safe 1accepts relative paths made from portable characters and rejects unsafe path forms. FFmpeg’s-safe 0allows any filename, but use it only when needed for trusted local paths. Quoting or escaping in the concat script follows FFmpeg’s rules, not shell-quoting assumptions. - Duration accuracy: FFmpeg warns that inaccurate file durations can cause timestamp artifacts because durations help position the next file.
- Older installations: FFmpeg’s online documentation is regenerated nightly and reflects the newest revision. For an older local build, consult the documentation installed with that version; see the FFmpeg documentation index.
Troubleshoot common problems
FFmpeg reports unsafe file paths
Keep the playlist and video paths relative and use portable names with -safe 1. If trusted local paths require spaces or special characters, escape or quote them using the concat demuxer’s syntax. Use -safe 0 only when the input paths are trusted and the less restrictive mode is necessary.
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Stream copy fails or the output has glitches
Check that all files have the same stream layout, codecs, and time bases. Also check the source durations. If the media does not match, stream copy may not be appropriate; normalize the files or use the concat filter with re-encoding as required.
The first episode repeats immediately after the last
Check the first and last entries in playlist.ffconcat. The script above reshuffles until they differ. If the playlist contains only one episode identity, no shuffle can create a different boundary.
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That is expected when repeatedly looping a fixed shuffled list. A boundary check only prevents an immediate repeat; use a scheduler with persistent recent-history state for a longer cooldown.
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