SubtitleEdit/subtitleedit · error · RiffParserException

Problem reading AVI header.

Error message

Problem reading AVI header.

What it means

DecodeAviHeader reads 'length' bytes for the AVIMAINHEADER chunk via RiffParser.ReadData; if fewer than 'length' bytes are returned the main AVI header is incomplete and cannot be decoded, so a RiffParserException is thrown. The downstream fields (frame rate, dimensions, stream count) all depend on a complete 56-byte header.

Source

Thrown at src/libse/ContainerFormats/RiffDecodeHeader.cs:243

        public static short GetShort(byte[] buffer, int index)
        {
            byte[] bytes = { buffer[index + 0], buffer[index + 1] };

            if (!BitConverter.IsLittleEndian)
            {
                Array.Reverse(bytes);
            }

            return BitConverter.ToInt16(bytes, 0);
        }

        private void DecodeAviHeader(RiffParser rp, int length)
        {
            var ba = new byte[length];
            if (rp.ReadData(ba, 0, length) != length)
            {
                throw new RiffParserException("Problem reading AVI header.");
            }

            _frameRate = GetInt(ba, 0);
            _maxBitRate = GetInt(ba, 4);
            _totalFrames = GetInt(ba, 16);
            _numStreams = GetInt(ba, 24);
            _width = GetInt(ba, 32);
            _height = GetInt(ba, 36);
        }

        private void DecodeAviStream(RiffParser rp, int length)
        {
            var ba = new byte[length];
            if (rp.ReadData(ba, 0, length) != length)
            {
                throw new RiffParserException("Problem reading AVI header.");
            }

View on GitHub (pinned to 17a9f07487)

Solutions

1. Re-acquire the full AVI file from source.
2. Before decoding, validate the declared 'avih' size is at least 56 bytes and matches remaining stream bytes.
3. Catch RiffParserException and report a corrupt-file error to the user.
4. Use a different container parser as a cross-check if the file must be salvaged.

Example fix

// before
var ba = new byte[length];
if (rp.ReadData(ba, 0, length) != length) throw new RiffParserException("Problem reading AVI header.");

// after
var ba = new byte[length];
int got = rp.ReadData(ba, 0, length);
if (got != length) throw new RiffParserException($"Short AVI header: read {got} of {length} bytes");

if (length < 56 || rp.BytesRemaining < length) throw new InvalidDataException($"AVI main header too short: {length}B");

try { header.DecodeAviHeader(rp, length); }
catch (RiffParserException ex) when (ex.Message.Contains("AVI header")) { /* corrupt; bail or salvage */ }

When it happens

Trigger: AVI file truncated inside the 'avih' chunk; RIFF nesting where the declared chunk size exceeds remaining data; RiffParser handed a stream positioned past the header.

Common situations: Partially downloaded AVI; AVI produced by a buggy encoder that wrote a short 'avih'; file written but not flushed/closed properly.

Related errors

• Element size mismatch for element {FromFourCc(fourCc)} need
• Unable to read. Corrupt RIFF file {FileName}
• MXF KLV packet - stream does not have 16 bytes available for
• Problem accessing RIFF file {FileName}
• Problem seeking in file {FileName}

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/0192707f87c4e47a. Report an issue: GitHub.