AlexxIT/go2rtc · error

probe reader overflow

Error message

probe reader overflow

What it means

pkg/core/readbuffer.go:63 implements a probe reader that records every byte it reads into an internal buffer, capped at r.BufferSize. When a single Read would push the recorded buffer beyond BufferSize (len(r.buf)+n > r.BufferSize), it refuses the read and returns "probe reader overflow". This is a library-internal invariant: the probe detection logic expected media probing to finish within a bounded number of bytes.

Solutions

  1. Increase BufferSize on the probe reader so it can hold enough bytes for your container's headers.
  2. Verify the media source is actually the expected format (a garbage/garbled stream may never be recognized).
  3. Check that the source produces a proper probeable stream (correct container, valid headers).
  4. If probing an unusual source (e.g. raw streams), bypass probing by declaring the codec explicitly.

Example fix

// before
core.NewProbeReader(rs, 4096)
// after: larger probe window for sources with long headers
core.NewProbeReader(rs, 512*1024)
Defensive patterns

Strategy: validation

Validate before calling

// ensure the probe window is large enough before probing
if probeReader.BufferSize < 512*1024 {
    probeReader = core.NewProbeReader(rs, 512*1024)
}

Try / catch

n, err := probeReader.Read(p)
if err != nil && err.Error() == "probe reader overflow" {
    return fmt.Errorf("media source exceeded probe window (%w); enlarge BufferSize or check source format", err)
}

Prevention

When it happens

Trigger: Any Read on the probe reader whose accumulated bytes plus the incoming chunk exceed r.BufferSize; triggered from TestReadSeeker or media probing when the source streams more data than the probe window before the format could be identified.

Common situations: Probing a media source with very large headers or no early recognizable format signature; misconfigured BufferSize too small for the container format; a source that never yields probeable data so the buffer fills to the cap.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of AlexxIT/go2rtc@c245815e75 (2026-09-07). Data as JSON: /api/errors/19db9441a89b8766. Report an issue: GitHub.

Appendix: source

Thrown at pkg/core/readbuffer.go:63

	// if buffer not empty - read from it
	if r.pos < len(r.buf) {
		n = copy(p, r.buf[r.pos:])
		r.pos += n
		return
	}

	// with negative buffer - empty it and read as usual
	if r.BufferSize < 0 {
		r.BufferSize = BufferDisable
		r.buf = nil
		r.pos = 0

		return r.Reader.Read(p)
	}

	n, err = r.Reader.Read(p)
	if len(r.buf)+n > r.BufferSize {
		return 0, errors.New("probe reader overflow")
	}
	r.buf = append(r.buf, p[:n]...)
	r.pos += n
	return
}

func (r *ReadBuffer) Close() error {
	if closer, ok := r.Reader.(io.Closer); ok {
		return closer.Close()
	}
	return nil
}

func (r *ReadBuffer) Seek(offset int64, whence int) (int64, error) {
	var pos int
	switch whence {
	case io.SeekStart:
		pos = int(offset)

View on GitHub (pinned to c245815e75)