SubtitleEdit/subtitleedit · error · RiffParserException

Problem accessing RIFF file {FileName}

Error message

Problem accessing RIFF file {FileName}

What it means

The catch-all in ReadTwoInts wraps any exception (IOException, ObjectDisposedException, NotSupportedException from a non-readable stream, etc.) raised during the 8-byte read into a RiffParserException with the 'Problem accessing RIFF file' message and the original as inner. It surfaces stream-level failures with the file name for context.

Source

Thrown at src/libse/ContainerFormats/RiffParser.cs:312

        /// <param name="fourCc">Output FourCC int</param>
        /// <param name="size">Output chunk/list size</param>
        public void ReadTwoInts(out int fourCc, out int size)
        {
            try
            {
                var buffer = new byte[TwoDWordSize];
                int readsize = _stream.Read(buffer, 0, TwoDWordSize);

                if (TwoDWordSize != readsize)
                {
                    throw new RiffParserException("Unable to read. Corrupt RIFF file " + FileName);
                }
                fourCc = RiffDecodeHeader.GetInt(buffer, 0);
                size = RiffDecodeHeader.GetInt(buffer, 4);
            }
            catch (Exception ex)
            {
                throw new RiffParserException("Problem accessing RIFF file " + FileName, ex);
            }
        }

        /// <summary>
        /// Non-thread-safe read a single int from the stream
        /// </summary>
        /// <param name="fourCc">Output int</param>
        public void ReadOneInt(out int fourCc)
        {
            try
            {
                var buffer = new byte[DWordSize];
                int readsize = _stream.Read(buffer, 0, DWordSize);
                if (DWordSize != readsize)
                {
                    throw new RiffParserException("Unable to read. Corrupt RIFF file " + FileName);
                }
                fourCc = RiffDecodeHeader.GetInt(buffer, 0);

View on GitHub (pinned to 17a9f07487)

Solutions

1. Inspect the InnerException to find the real I/O cause.
2. Ensure the stream stays open and readable for the parser's lifetime (do not dispose prematurely).
3. Open the file with FileShare.ReadWrite to avoid lock contention.
4. Retry the whole parse once on transient I/O errors.

Example fix

// before
catch (Exception ex) { throw new RiffParserException("Problem accessing RIFF file " + FileName, ex); }

// after
catch (Exception ex) when (!(ex is RiffParserException)) { throw new RiffParserException($"Problem accessing RIFF file {FileName} at {_stream?.Position}", ex); }

if (stream == null) throw new ArgumentNullException(nameof(stream));
if (!stream.CanRead) throw new ArgumentException("stream must be readable", nameof(stream));

try { rp.ReadTwoInts(out fcc, out size); }
catch (RiffParserException ex) { var root = ex.InnerException ?? ex; /* handle I/O root */ }

When it happens

Trigger: Underlying stream throws (closed/disposed, network drop, unreadable stream, security/permission denial); disk error during read.

Common situations: Network share disconnect mid-read; file deleted or locked by another process during parse; stream wrapped over a closed resource.

Related errors

• Problem reading data in file {FileName}
• Unable to read. Corrupt RIFF file {FileName}
• Problem reading AVI header.
• Element size mismatch for element {FromFourCc(fourCc)} need
• Problem seeking in file {FileName}

AI-assisted analysis of SubtitleEdit/subtitleedit@17a9f07487 (2026-08-13). Data as JSON: /api/errors/4a6963bdcb94276f. Report an issue: GitHub.