TeamNewPipe/NewPipe · error · RuntimeException

Cluster element found without Info and/or Tracks element at

Error message

Cluster element found without Info and/or Tracks element at position {}

What it means

Thrown by WebMReader when parsing a Matroska/WebM Segment element: the parser encountered a Cluster (the media-data container) before it saw the required Info and/or Tracks metadata elements. In a well-formed WebM file the Info element (codec/duration/timecode-scale metadata) and Tracks element (stream descriptions) must precede the first Cluster. The reader only sets metadataExpected when it knows the segment is not a live stream, so this fires on structurally invalid or truncated files where the metadata section is missing or was cut off before the Cluster began.

Source

Thrown at app/src/main/java/org/schabi/newpipe/streams/WebMReader.java:294

        Element elem;
        while ((elem = untilElement(ref, ID_INFO, ID_TRACKS, ID_CLUSTER)) != null) {
            if (elem.type == ID_CLUSTER) {
                obj.currentCluster = elem;
                break;
            }
            switch (elem.type) {
                case ID_INFO:
                    obj.info = readInfo(elem);
                    break;
                case ID_TRACKS:
                    obj.tracks = readTracks(elem, trackLacingExpected);
                    break;
            }
            ensure(elem);
        }

        if (metadataExpected && (obj.info == null || obj.tracks == null)) {
            throw new RuntimeException(
                    "Cluster element found without Info and/or Tracks element at position "
                            + ref.offset);
        }

        return obj;
    }

    private WebMTrack[] readTracks(final Element ref, final int lacingExpected) throws IOException {
        final ArrayList<WebMTrack> trackEntries = new ArrayList<>(2);
        Element elemTrackEntry;

        while ((elemTrackEntry = untilElement(ref, ID_TRACK_ENTRY)) != null) {
            final WebMTrack entry = new WebMTrack();
            boolean drop = false;
            Element elem;
            while ((elem = untilElement(elemTrackEntry)) != null) {
                switch (elem.type) {
                    case ID_TRACK_NUMBER:

View on GitHub (pinned to 9e8be09156)

Solutions

Validate the source file is complete and well-formed before feeding it to WebMReader (check download finished, file size matches expected Content-Length).
Re-download or re-extract the stream: the metadata section was missing or truncated, indicating the source file is damaged.
If reading a live stream or segment that legitimately omits metadata, construct the reader so metadataExpected is false (the overload that knows this is a continuation/live segment).
Catch the RuntimeException at the call site and surface a user-facing 'media file is corrupt' message rather than crashing.

Example fix

// before — crashes on truncated downloads
WebMReader reader = new WebMReader(stream);
Segment segment = reader.parse();

// after — guard against corrupt/truncated media
try {
    WebMReader reader = new WebMReader(stream);
    Segment segment = reader.parse();
} catch (RuntimeException e) {
    if (e.getMessage().contains("Cluster element found without")) {
        throw new IOException("Corrupt WebM file: missing Info/Tracks metadata", e);
    }
    throw e;
}

Defensive patterns

Strategy: validation

Validate before calling

// Verify the WebM stream has Info and Tracks before the first Cluster
// by doing a lightweight EBML pre-scan, or check file completeness:
if (streamFile.length() < minExpectedSize) {
    throw new IOException("WebM source too small / likely truncated: " + streamFile.length());
}

Try / catch

try {
    WebMReader reader = new WebMReader(stream);
    Segment seg = reader.parse();
} catch (RuntimeException e) {
    if (e.getMessage() != null && e.getMessage().contains("Cluster element found without")) {
        // treat as corrupt/incomplete source — re-download or skip
        throw new IOException("Corrupt WebM: missing Info/Tracks metadata", e);
    }
    throw e;
}

Prevention

Always verify a download completed fully (Content-Length matched) before demuxing.
Validate WebM magic bytes (0x1A45DFA3) at the start of the file before parsing.
Do not attempt to demux partial/live segments as full WebM files.

When it happens

Trigger: readSegment() is called with metadataExpected=true; the while-loop breaks on the first ID_CLUSTER element (line 278-281) before both obj.info and obj.tracks are populated; the post-loop check at line 293 finds one or both null and throws. This happens when the stream's Segment starts directly with a Cluster, or when Info/Tracks appear after the Cluster instead of before it.

Common situations: Downloading a truncated or partially-written WebM/Opus audio file (e.g. download interrupted mid-write); receiving a live DASH/HLS WebM adaptation that omits the head metadata when saved; a remuxing tool that reordered EBML elements incorrectly; corrupt media cache left over from a failed download.

Related errors

AI-assisted analysis of TeamNewPipe/NewPipe@9e8be09156 (2026-08-14). Data as JSON: /api/errors/3e41ae2df87970f6. Report an issue: GitHub.