Preview generation fallback (#725)

* Added preview generation fallback feature.
When a preview generation fails (often for wmv/avi files), the new code tries with less stricted (no xerror) and more time consuming options (slow+fast seek).
Fix a minor issue when stash downloads ffmpeg/ffprobe, but doesn't re-detect their paths.

.gitignore

@@ -48,6 +48,9 @@ ui/v2.5/src/core/generated-*.tsx
 .idea/**/uiDesigner.xml
 .idea/**/dbnavigator.xml
 
+# Goland Junk
+pkg/pkg
+
 ####
 # Random
 ####
@@ -58,3 +61,4 @@ node_modules
 
 stash
 dist
+.DS_Store

pkg/ffmpeg/encoder_scene_preview_chunk.go

@@ -14,12 +14,51 @@ type ScenePreviewChunkOptions struct {
 	OutputPath string
 }
 
-func (e *Encoder) ScenePreviewVideoChunk(probeResult VideoFile, options ScenePreviewChunkOptions, preset string) {
+func (e *Encoder) ScenePreviewVideoChunk(probeResult VideoFile, options ScenePreviewChunkOptions, preset string, fallback bool) error {
+	var fastSeek float64
+	var slowSeek float64
+	fallbackMinSlowSeek := 20.0
+
 	args := []string{
 		"-v", "error",
-		"-xerror",
-		"-ss", strconv.FormatFloat(options.StartTime, 'f', 2, 64),
-		"-i", probeResult.Path,
+	}
+
+	// Non-fallback: enable xerror.
+	// "-xerror" causes ffmpeg to fail on warnings, often the preview is fine but could be broken.
+	if !fallback {
+		args = append(args, "-xerror")
+		fastSeek = options.StartTime
+		slowSeek = 0
+	} else {
+		// In fallback mode, disable "-xerror" and try a combination of fast/slow seek instead of just fastseek
+		// Commonly with avi/wmv ffmpeg doesn't seem to always predict the right start point to begin decoding when
+		// using fast seek. If you force ffmpeg to decode more, it avoids the "blocky green artifact" issue.
+		if options.StartTime > fallbackMinSlowSeek {
+			// Handle seeks longer than fallbackMinSlowSeek with fast/slow seeks
+			// Allow for at least fallbackMinSlowSeek seconds of slow seek
+			fastSeek = options.StartTime - fallbackMinSlowSeek
+			slowSeek = fallbackMinSlowSeek
+		} else {
+			// Handle seeks shorter than fallbackMinSlowSeek with only slow seeks.
+			slowSeek = options.StartTime
+			fastSeek = 0
+		}
+	}
+
+	if fastSeek > 0 {
+		args = append(args, "-ss")
+		args = append(args, strconv.FormatFloat(fastSeek, 'f', 2, 64))
+	}
+
+	args = append(args, "-i")
+	args = append(args, probeResult.Path)
+
+	if slowSeek > 0 {
+		args = append(args, "-ss")
+		args = append(args, strconv.FormatFloat(slowSeek, 'f', 2, 64))
+	}
+
+	args2 := []string{
 		"-t", strconv.FormatFloat(options.Duration, 'f', 2, 64),
 		"-max_muxing_queue_size", "1024", // https://trac.ffmpeg.org/ticket/6375
 		"-y",
@@ -36,10 +75,14 @@ func (e *Encoder) ScenePreviewVideoChunk(probeResult VideoFile, options ScenePre
 		"-strict", "-2",
 		options.OutputPath,
 	}
-	_, _ = e.run(probeResult, args)
+
+	finalArgs := append(args, args2...)
+
+	_, err := e.run(probeResult, finalArgs)
+	return err
 }
 
-func (e *Encoder) ScenePreviewVideoChunkCombine(probeResult VideoFile, concatFilePath string, outputPath string) {
+func (e *Encoder) ScenePreviewVideoChunkCombine(probeResult VideoFile, concatFilePath string, outputPath string) error {
 	args := []string{
 		"-v", "error",
 		"-f", "concat",
@@ -48,7 +91,8 @@ func (e *Encoder) ScenePreviewVideoChunkCombine(probeResult VideoFile, concatFil
 		"-c", "copy",
 		outputPath,
 	}
-	_, _ = e.run(probeResult, args)
+	_, err := e.run(probeResult, args)
+	return err
 }
 
 func (e *Encoder) ScenePreviewVideoToImage(probeResult VideoFile, width int, videoPreviewPath string, outputPath string) error {

pkg/ffmpeg/encoder_screenshot.go

@@ -21,7 +21,7 @@ func (e *Encoder) Screenshot(probeResult VideoFile, options ScreenshotOptions) e
 		"-v", options.Verbosity,
 		"-ss", fmt.Sprintf("%v", options.Time),
 		"-y",
-		"-i", probeResult.Path, // TODO: Wrap in quotes?
+		"-i", probeResult.Path,
 		"-vframes", "1",
 		"-q:v", fmt.Sprintf("%v", options.Quality),
 		"-vf", fmt.Sprintf("scale=%v:-1", options.Width),

pkg/manager/generator_preview.go

@@ -62,8 +62,11 @@ func (g *PreviewGenerator) Generate() error {
 	}
 
 	if g.GenerateVideo {
-		if err := g.generateVideo(&encoder); err != nil {
-			return err
+		if err := g.generateVideo(&encoder, false); err != nil {
+			logger.Warnf("[generator] failed generating scene preview, trying fallback")
+			if err := g.generateVideo(&encoder, true); err != nil {
+				return err
+			}
 		}
 	}
 	if g.GenerateImage {
@@ -90,7 +93,7 @@ func (g *PreviewGenerator) generateConcatFile() error {
 	return w.Flush()
 }
 
-func (g *PreviewGenerator) generateVideo(encoder *ffmpeg.Encoder) error {
+func (g *PreviewGenerator) generateVideo(encoder *ffmpeg.Encoder, fallback bool) error {
 	outputPath := filepath.Join(g.OutputDirectory, g.VideoFilename)
 	outputExists, _ := utils.FileExists(outputPath)
 	if !g.Overwrite && outputExists {
@@ -111,11 +114,15 @@ func (g *PreviewGenerator) generateVideo(encoder *ffmpeg.Encoder) error {
 			Width:      640,
 			OutputPath: chunkOutputPath,
 		}
-		encoder.ScenePreviewVideoChunk(g.Info.VideoFile, options, g.PreviewPreset)
+		if err := encoder.ScenePreviewVideoChunk(g.Info.VideoFile, options, g.PreviewPreset, fallback); err != nil {
+			return err
+		}
 	}
 
 	videoOutputPath := filepath.Join(g.OutputDirectory, g.VideoFilename)
-	encoder.ScenePreviewVideoChunkCombine(g.Info.VideoFile, g.getConcatFilePath(), videoOutputPath)
+	if err := encoder.ScenePreviewVideoChunkCombine(g.Info.VideoFile, g.getConcatFilePath(), videoOutputPath); err != nil {
+		return err
+	}
 	logger.Debug("created video preview: ", videoOutputPath)
 	return nil
 }

pkg/manager/manager.go

@@ -145,10 +145,12 @@ The FFMPEG and FFProbe binaries should be placed in %s
 The error was: %s
 `
 			logger.Fatalf(msg, configDirectory, err)
+		} else {
+			// After download get new paths for ffmpeg and ffprobe
+			ffmpegPath, ffprobePath = ffmpeg.GetPaths(configDirectory)
 		}
 	}
 
-	// TODO: is this valid after download?
 	instance.FFMPEGPath = ffmpegPath
 	instance.FFProbePath = ffprobePath
 }

ui/v2.5/src/components/Changelog/versions/v030.tsx

@@ -19,6 +19,7 @@ const markup = `
 *  Add support for parent/child studios.
 
 ### 🎨 Improvements
+*  Make preview generation more fault-tolerant.
 *  Allow clearing of images and querying on missing images.
 *  Allow free-editing of scene movie number.
 *  Allow adding performers and studios from selectors.