What causes "expected {} found {}" in TeamNewPipe/NewPipe?

Re-download/re-mux; the box sequence does not match what this strict reader expects.

TeamNewPipe/NewPipe · error · NoSuchElementException

expected {} found {}

Error message

expected {} found {}

What it means

Mp4DashReader.readBox(expected) reads a box and compares its 4-byte type against the expected atom constant. If they differ it throws NoSuchElementException naming both expected and found atoms. This is a structural guard used during ftyp parsing and full-box reads where the next box must be a specific type; a mismatch means the file layout diverged from what the parser assumes.

Source

Thrown at app/src/main/java/org/schabi/newpipe/streams/Mp4DashReader.java:281

    }

    private Box readBox() throws IOException {
        final Box b = new Box();
        b.offset = stream.position();
        b.size = stream.readUnsignedInt();
        b.type = stream.readInt();

        if (b.size == 1) {
            b.size = stream.readLong();
        }

        return b;
    }

    private Box readBox(final int expected) throws IOException {
        final Box b = readBox();
        if (b.type != expected) {
            throw new NoSuchElementException("expected " + boxName(expected)
                    + " found " + boxName(b));
        }
        return b;
    }

    private byte[] readFullBox(final Box ref) throws IOException {
        // full box reading is limited to 2 GiB, and should be enough
        final int size = (int) ref.size;

        final ByteBuffer buffer = ByteBuffer.allocate(size);
        buffer.putInt(size);
        buffer.putInt(ref.type);

        final int read = size - 8;

        if (stream.read(buffer.array(), 8, read) != read) {
            throw new EOFException(String.format("EOF reached in box: type=%s offset=%s size=%s",
                    boxName(ref.type), ref.offset, ref.size));

View on GitHub (pinned to 9e8be09156)

Solutions

Re-download/re-mux; the box sequence does not match what this strict reader expects.
Use a more tolerant MP4 inspector (mp4info/MP4Box) to identify which box is misplaced and re-emit the file correctly.
If you only need specific boxes, use untilBox() (which skips unknown boxes) instead of readBox(expected).
Catch NoSuchElementException at the parse boundary and report the structural mismatch.

Example fix

// before — strict read that fails on an unexpected leading box
Box b = readBox(ATOM_FTYP); // throws if a non-ftyp box leads

// after — skip until the expected box is found
Box b = untilBox(null, ATOM_FTYP);
if (b == null) throw new IOException("ftyp box missing entirely");

Defensive patterns

Strategy: try-catch

Validate before calling

// Prefer untilBox() to skip unknown boxes instead of readBox(expected).
// Before a strict read, scan forward to the expected box:
Box b = untilBox(parent, ATOM_FTYP);
if (b == null) throw new IOException("required box ftyp not present");

Type guard

// A box-type narrowing helper:
public static Box expectBox(Box b, int expected) throws NoSuchElementException {
    if (b.type != expected)
        throw new NoSuchElementException("expected "+boxName(expected)+" found "+boxName(b));
    return b;
}

Try / catch

try {
    Box b = readBox(ATOM_FTYP);
} catch (NoSuchElementException e) {
    if (e.getMessage().startsWith("expected")) {
        // unexpected leading box — try skipping one box and retry, or reject the file
        Log.w(TAG, "box order unexpected: " + e.getMessage());
    } else throw e;
}

Prevention

Use untilBox() for tolerant scanning; reserve readBox(expected) for invariants.
Re-mux non-conformant files with ffmpeg/MP4Box.
Validate box order with mp4info before strict parsing.
Do not assume a specific box leads the file without sniffing.

When it happens

Trigger: Calling readBox(expected) when the stream position points at a different box type than anticipated — e.g. expecting ATOM_FTYP but finding another atom, or any ordered-box-read where the next box is not the assumed type. Happens when a box is unexpectedly absent/extra/reordered.

Common situations: A non-conformant MP4 where boxes are in an unusual order; an extra metadata box inserted by a tagging tool before ftyp; a truncated file whose remaining bytes decode to an unexpected atom type; an encrypted/DRM'd file with altered structure.

Related errors

AI-assisted analysis of TeamNewPipe/NewPipe@9e8be09156 (2026-08-14). Data as JSON: /api/errors/84e076c17070e0e7. Report an issue: GitHub.