From cab108a8395bca7afbc0f0b587b55c13d4bc0d2a Mon Sep 17 00:00:00 2001 From: Marc Brooks Date: Fri, 17 Jul 2026 16:23:57 -0500 Subject: Prevent ffmpeg from hanging extracting subtitles (#17297) * Prevent ffmpeg from hanging extracting subtitles Add `RunSubtitleExtractionProcess` to unify the external _ffmpeg_ process handling and error management. Add a `-nostdin` flag that prevents _ffmpeg_ from reading from _stdin_ and blocking on an inherited stdin handle (e.g. when Jellyfin runs as a service under NSSM), which otherwise hangs subtitle extraction forever when _ffmpeg_ blocks on any keyboard-interaction read until the timeout (30 minutes). Close the redirected _stdin_ to ensure immediage EOF. Drain the _stderr_ to a string and log it, to ensure we don't block the _ffmpeg_ process on errors that exceed the pipe length. Pass `-y` to _ffmpeg_ to ensure it overwrites any existing output file without prompting for confirmation. * Address review comments Make sure we always drain stderr. Make sure the timeout also honors the cancellationToken. Make sure when we get cancelled we don't log it as a ffmpeg error. --- .../Subtitles/SubtitleEncoder.cs | 240 +++++---------------- 1 file changed, 57 insertions(+), 183 deletions(-) (limited to 'MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs') diff --git a/MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs b/MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs index 5301f52e01..28f7b92268 100644 --- a/MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs +++ b/MediaBrowser.MediaEncoding/Subtitles/SubtitleEncoder.cs @@ -445,98 +445,15 @@ namespace MediaBrowser.MediaEncoding.Subtitles encodingParam = " -sub_charenc " + encodingParam; } - int exitCode; - - using (var process = new Process - { - StartInfo = new ProcessStartInfo - { - CreateNoWindow = true, - UseShellExecute = false, - FileName = _mediaEncoder.EncoderPath, - Arguments = string.Format(CultureInfo.InvariantCulture, "-y {0} -i \"{1}\" -c:s srt \"{2}\"", encodingParam, inputPath, outputPath), - WindowStyle = ProcessWindowStyle.Hidden, - ErrorDialog = false - }, - EnableRaisingEvents = true - }) - { - _logger.LogInformation("{0} {1}", process.StartInfo.FileName, process.StartInfo.Arguments); - - try - { - process.Start(); - } - catch (Exception ex) - { - _logger.LogError(ex, "Error starting ffmpeg"); - - throw; - } - - try - { - var timeoutMinutes = _serverConfigurationManager.GetEncodingOptions().SubtitleExtractionTimeoutMinutes; - await process.WaitForExitAsync(TimeSpan.FromMinutes(timeoutMinutes)).ConfigureAwait(false); - exitCode = process.ExitCode; - } - catch (OperationCanceledException) - { - process.Kill(true); - exitCode = -1; - } - } - - var failed = false; + var args = string.Format(CultureInfo.InvariantCulture, "-y {0} -i \"{1}\" -c:s srt \"{2}\"", encodingParam, inputPath, outputPath); - if (exitCode == -1) - { - failed = true; - - if (File.Exists(outputPath)) - { - try - { - _logger.LogInformation("Deleting converted subtitle due to failure: {Path}", outputPath); - _fileSystem.DeleteFile(outputPath); - } - catch (IOException ex) - { - _logger.LogError(ex, "Error deleting converted subtitle {Path}", outputPath); - } - } - } - else if (!File.Exists(outputPath) || _fileSystem.GetFileInfo(outputPath).Length == 0) - { - failed = true; - - try - { - _logger.LogWarning("Deleting converted subtitle due to failure: {Path}", outputPath); - _fileSystem.DeleteFile(outputPath); - } - catch (FileNotFoundException) - { - } - catch (IOException ex) - { - _logger.LogError(ex, "Error deleting converted subtitle {Path}", outputPath); - } - } - - if (failed) - { - _logger.LogError("ffmpeg subtitle conversion failed for {Path}", inputPath); - - throw new FfmpegException( - string.Format(CultureInfo.InvariantCulture, "ffmpeg subtitle conversion failed for {0}", inputPath)); - } - - await SetAssFont(outputPath, cancellationToken).ConfigureAwait(false); + await ExtractSubtitlesForFile( + inputPath, + args, + [outputPath], + cancellationToken).ConfigureAwait(false); WriteCacheMeta(outputPath, inputPath); - - _logger.LogInformation("ffmpeg subtitle conversion succeeded for {Path}", inputPath); } private string GetExtractableSubtitleFormat(MediaStream subtitleStream) @@ -727,7 +644,7 @@ namespace MediaBrowser.MediaEncoding.Subtitles var outputPaths = new List(); var args = string.Format( CultureInfo.InvariantCulture, - "-i {0}", + "-y -i {0}", inputPath); foreach (var subtitleStream in subtitleStreams) @@ -781,50 +698,10 @@ namespace MediaBrowser.MediaEncoding.Subtitles private async Task ExtractSubtitlesForFile( string inputPath, string args, - List outputPaths, + IReadOnlyList outputPaths, CancellationToken cancellationToken) { - int exitCode; - - using (var process = new Process - { - StartInfo = new ProcessStartInfo - { - CreateNoWindow = true, - UseShellExecute = false, - FileName = _mediaEncoder.EncoderPath, - Arguments = args, - WindowStyle = ProcessWindowStyle.Hidden, - ErrorDialog = false - }, - EnableRaisingEvents = true - }) - { - _logger.LogInformation("{File} {Arguments}", process.StartInfo.FileName, process.StartInfo.Arguments); - - try - { - process.Start(); - } - catch (Exception ex) - { - _logger.LogError(ex, "Error starting ffmpeg"); - - throw; - } - - try - { - var timeoutMinutes = _serverConfigurationManager.GetEncodingOptions().SubtitleExtractionTimeoutMinutes; - await process.WaitForExitAsync(TimeSpan.FromMinutes(timeoutMinutes)).ConfigureAwait(false); - exitCode = process.ExitCode; - } - catch (OperationCanceledException) - { - process.Kill(true); - exitCode = -1; - } - } + var (exitCode, ffmpegError) = await RunSubtitleExtractionProcess(args, cancellationToken).ConfigureAwait(false); var failed = false; @@ -884,6 +761,13 @@ namespace MediaBrowser.MediaEncoding.Subtitles if (failed) { + cancellationToken.ThrowIfCancellationRequested(); + + if (!string.IsNullOrWhiteSpace(ffmpegError)) + { + _logger.LogError("ffmpeg subtitle extraction failed for {InputPath}: {FfmpegOutput}", inputPath, ffmpegError); + } + throw new FfmpegException( string.Format(CultureInfo.InvariantCulture, "ffmpeg subtitle extraction failed for {0}", inputPath)); } @@ -941,16 +825,38 @@ namespace MediaBrowser.MediaEncoding.Subtitles ArgumentException.ThrowIfNullOrEmpty(outputPath); Directory.CreateDirectory(Path.GetDirectoryName(outputPath) ?? throw new ArgumentException($"Provided path ({outputPath}) is not valid.", nameof(outputPath))); - var processArgs = string.Format( CultureInfo.InvariantCulture, - "-i {0} -copyts -map 0:{1} -an -vn -c:s {2} \"{3}\"", + "-y -i {0} -copyts -map 0:{1} -an -vn -c:s {2} \"{3}\"", inputPath, subtitleStreamIndex, outputCodec, outputPath); + await ExtractSubtitlesForFile( + inputPath, + processArgs, + [outputPath], + cancellationToken).ConfigureAwait(false); + } + + /// + /// Runs ffmpeg to extract or convert subtitles, capturing its exit code and stderr output. + /// + /// + /// stdin is redirected and closed, and -nostdin is prepended to the arguments, so ffmpeg can never + /// block reading an inherited stdin handle (which happens when Jellyfin runs as a service, e.g. under NSSM, + /// and stalls subtitle extraction until the timeout). stderr is redirected and drained so a full pipe buffer + /// cannot deadlock ffmpeg and so its output can be surfaced on failure; stdout is left un-redirected as it is + /// unused for subtitle extraction. + /// + /// The ffmpeg command line arguments. + /// The cancellation token. + /// The ffmpeg exit code (-1 on timeout) and its captured stderr output. + private async Task<(int ExitCode, string StandardError)> RunSubtitleExtractionProcess(string arguments, CancellationToken cancellationToken) + { int exitCode; + var standardError = string.Empty; using (var process = new Process { @@ -958,8 +864,10 @@ namespace MediaBrowser.MediaEncoding.Subtitles { CreateNoWindow = true, UseShellExecute = false, + RedirectStandardInput = true, + RedirectStandardError = true, FileName = _mediaEncoder.EncoderPath, - Arguments = processArgs, + Arguments = "-nostdin " + arguments, WindowStyle = ProcessWindowStyle.Hidden, ErrorDialog = false }, @@ -975,14 +883,21 @@ namespace MediaBrowser.MediaEncoding.Subtitles catch (Exception ex) { _logger.LogError(ex, "Error starting ffmpeg"); - throw; } + // Close stdin so ffmpeg observes EOF instead of blocking on an inherited handle. + process.StandardInput.Close(); + + // Begin draining stderr before waiting for exit; a full stderr pipe buffer would otherwise deadlock ffmpeg. + var standardErrorTask = process.StandardError.ReadToEndAsync(CancellationToken.None); + var timeoutMinutes = _serverConfigurationManager.GetEncodingOptions().SubtitleExtractionTimeoutMinutes; + using var waitSource = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken); + waitSource.CancelAfter(TimeSpan.FromMinutes(timeoutMinutes)); + try { - var timeoutMinutes = _serverConfigurationManager.GetEncodingOptions().SubtitleExtractionTimeoutMinutes; - await process.WaitForExitAsync(TimeSpan.FromMinutes(timeoutMinutes)).ConfigureAwait(false); + await process.WaitForExitAsync(waitSource.Token).ConfigureAwait(false); exitCode = process.ExitCode; } catch (OperationCanceledException) @@ -990,59 +905,18 @@ namespace MediaBrowser.MediaEncoding.Subtitles process.Kill(true); exitCode = -1; } - } - - var failed = false; - - if (exitCode == -1) - { - failed = true; try { - _logger.LogWarning("Deleting extracted subtitle due to failure: {Path}", outputPath); - _fileSystem.DeleteFile(outputPath); - } - catch (FileNotFoundException) - { - } - catch (IOException ex) - { - _logger.LogError(ex, "Error deleting extracted subtitle {Path}", outputPath); + standardError = await standardErrorTask.ConfigureAwait(false); } - } - else if (!File.Exists(outputPath) || _fileSystem.GetFileInfo(outputPath).Length == 0) - { - failed = true; - - try - { - _logger.LogWarning("Deleting extracted subtitle due to failure: {Path}", outputPath); - _fileSystem.DeleteFile(outputPath); - } - catch (FileNotFoundException) - { - } - catch (IOException ex) + catch (OperationCanceledException) { - _logger.LogError(ex, "Error deleting extracted subtitle {Path}", outputPath); + // Reading ffmpeg output was cancelled; nothing more to capture. } } - if (failed) - { - _logger.LogError("ffmpeg subtitle extraction failed for {InputPath} to {OutputPath}", inputPath, outputPath); - - throw new FfmpegException( - string.Format(CultureInfo.InvariantCulture, "ffmpeg subtitle extraction failed for {0} to {1}", inputPath, outputPath)); - } - - _logger.LogInformation("ffmpeg subtitle extraction completed for {InputPath} to {OutputPath}", inputPath, outputPath); - - if (string.Equals(outputCodec, "ass", StringComparison.OrdinalIgnoreCase)) - { - await SetAssFont(outputPath, cancellationToken).ConfigureAwait(false); - } + return (exitCode, standardError); } /// -- cgit v1.2.3