What causes "stream is nil" in pion/webrtc?

Ensure the io.Reader is non-nil before calling NewReader; check errors from the code that creates it.

stream is nil

Error message

stream is nil

What it means

This error is returned by h265reader.NewReader when the io.Reader argument is nil. H265Reader needs an underlying stream to parse an H265/HEVC Annex-B bitstream; a nil reader cannot be used. It is the HEVC counterpart of errNilReader in h264reader.

Source

Thrown at pkg/media/h265reader/h265reader.go:25

import (
	"bytes"
	"errors"
	"io"
)

// H265Reader reads data from stream and constructs h265 nal units.
type H265Reader struct {
	stream                      io.Reader
	nalBuffer                   []byte
	countOfConsecutiveZeroBytes int
	nalPrefixParsed             bool
	readBuffer                  []byte
	tmpReadBuf                  []byte
	includeSEI                  bool
}

var (
	errNilReader           = errors.New("stream is nil")
	errDataIsNotH265Stream = errors.New("data is not a H265/HEVC bitstream")
)

func (reader *H265Reader) shouldSkipNAL(naluType NalUnitType) bool {
	return !reader.includeSEI && (naluType == NalUnitTypePrefixSei || naluType == NalUnitTypeSuffixSei)
}

// NewReader creates new H265Reader.
func NewReader(in io.Reader) (*H265Reader, error) {
	if in == nil {
		return nil, errNilReader
	}

	reader := &H265Reader{
		stream:          in,
		nalBuffer:       make([]byte, 0),
		nalPrefixParsed: false,
		readBuffer:      make([]byte, 0),

View on GitHub (pinned to 8c25dc09fa)

Solutions

Ensure the io.Reader is non-nil before calling NewReader; check errors from the code that creates it.
Match on errors.Is(err, <h265reader nil sentinel>) to produce a clearer message.
Fail fast with a contextual error at the call site.

Example fix

// before
rdr, err := h265reader.NewReader(stream) // stream may be nil
// after
if stream == nil {
    return nil, errors.New("HEVC input stream is nil")
}
rdr, err := h265reader.NewReader(stream)

Defensive patterns

Strategy: validation

Validate before calling

if stream == nil {
    return errors.New("h265 input stream is nil")
}
rdr, err := h265reader.NewReader(stream)

Type guard

func hasReader(r io.Reader) bool { return r != nil }

Try / catch

rdr, err := h265reader.NewReader(stream)
if err != nil {
    return fmt.Errorf("h265reader init: %w", err)
}

Prevention

Check upstream open/creation errors before constructing the reader.
Keep stream initialization and reader construction in the same error-checked path.
Fail fast with contextual errors instead of passing nil downward.

When it happens

Trigger: Calling h265reader.NewReader(nil), usually because the stream variable was never initialized or an upstream opener failed without being checked.

Common situations: Unchecked errors from os.Open or a network dial resulting in a nil reader; refactoring that removed stream initialization; conditionally-created sources that end up nil.

Related errors

AI-assisted analysis of pion/webrtc@8c25dc09fa (2026-09-03). Data as JSON: /api/errors/99ae3117257b1fc1. Report an issue: GitHub.