From 31a74708653b2567c45b2db0b25db5f68d41c2ef Mon Sep 17 00:00:00 2001
From: Lin Tianchuan <47070449+1024th@users.noreply.github.com>
Date: Fri, 10 Jan 2025 20:48:45 +0800
Subject: [PATCH] feat(local): support both time and percent for video
 thumbnail (#7802)

* feat(local): support percent for video thumbnail

The percentage determines the point in the video (as a percentage of the total duration) at which the thumbnail will be generated.

* feat(local): support both time and percent for video thumbnail
---
 drivers/local/driver.go | 22 ++++++++++++++++
 drivers/local/meta.go   |  1 +
 drivers/local/util.go   | 58 ++++++++++++++++++++++++++++++++++++++---
 3 files changed, 77 insertions(+), 4 deletions(-)

diff --git a/drivers/local/driver.go b/drivers/local/driver.go
index 2519232e..8a804ef3 100644
--- a/drivers/local/driver.go
+++ b/drivers/local/driver.go
@@ -79,6 +79,28 @@ func (d *Local) Init(ctx context.Context) error {
 	} else {
 		d.thumbTokenBucket = NewStaticTokenBucketWithMigration(d.thumbTokenBucket, d.thumbConcurrency)
 	}
+	// Check the VideoThumbPos value
+	if d.VideoThumbPos == "" {
+		d.VideoThumbPos = "20%"
+	}
+	if strings.HasSuffix(d.VideoThumbPos, "%") {
+		percentage := strings.TrimSuffix(d.VideoThumbPos, "%")
+		val, err := strconv.ParseFloat(percentage, 64)
+		if err != nil {
+			return fmt.Errorf("invalid video_thumb_pos value: %s, err: %s", d.VideoThumbPos, err)
+		}
+		if val < 0 || val > 100 {
+			return fmt.Errorf("invalid video_thumb_pos value: %s, the precentage must be a number between 0 and 100", d.VideoThumbPos)
+		}
+	} else {
+		val, err := strconv.ParseFloat(d.VideoThumbPos, 64)
+		if err != nil {
+			return fmt.Errorf("invalid video_thumb_pos value: %s, err: %s", d.VideoThumbPos, err)
+		}
+		if val < 0 {
+			return fmt.Errorf("invalid video_thumb_pos value: %s, the time must be a positive number", d.VideoThumbPos)
+		}
+	}
 	return nil
 }
 
diff --git a/drivers/local/meta.go b/drivers/local/meta.go
index 5ffac920..14b0404f 100644
--- a/drivers/local/meta.go
+++ b/drivers/local/meta.go
@@ -10,6 +10,7 @@ type Addition struct {
 	Thumbnail        bool   `json:"thumbnail" required:"true" help:"enable thumbnail"`
 	ThumbCacheFolder string `json:"thumb_cache_folder"`
 	ThumbConcurrency string `json:"thumb_concurrency" default:"16" required:"false" help:"Number of concurrent thumbnail generation goroutines. This controls how many thumbnails can be generated in parallel."`
+	VideoThumbPos    string `json:"video_thumb_pos" default:"20%" required:"false" help:"The position of the video thumbnail. If the value is a number (integer ot floating point), it represents the time in seconds. If the value ends with '%', it represents the percentage of the video duration."`
 	ShowHidden       bool   `json:"show_hidden" default:"true" required:"false" help:"show hidden directories and files"`
 	MkdirPerm        string `json:"mkdir_perm" default:"777"`
 	RecycleBinPath   string `json:"recycle_bin_path" default:"delete permanently" help:"path to recycle bin, delete permanently if empty or keep 'delete permanently'"`
diff --git a/drivers/local/util.go b/drivers/local/util.go
index b994c205..d2fbd097 100644
--- a/drivers/local/util.go
+++ b/drivers/local/util.go
@@ -2,11 +2,13 @@ package local
 
 import (
 	"bytes"
+	"encoding/json"
 	"fmt"
 	"io/fs"
 	"os"
 	"path/filepath"
 	"sort"
+	"strconv"
 	"strings"
 
 	"github.com/alist-org/alist/v3/internal/conf"
@@ -34,10 +36,58 @@ func isSymlinkDir(f fs.FileInfo, path string) bool {
 	return false
 }
 
-func GetSnapshot(videoPath string, frameNum int) (imgData *bytes.Buffer, err error) {
+// Get the snapshot of the video
+func (d *Local) GetSnapshot(videoPath string) (imgData *bytes.Buffer, err error) {
+	// Run ffprobe to get the video duration
+	jsonOutput, err := ffmpeg.Probe(videoPath)
+	if err != nil {
+		return nil, err
+	}
+	// get format.duration from the json string
+	type probeFormat struct {
+		Duration string `json:"duration"`
+	}
+	type probeData struct {
+		Format probeFormat `json:"format"`
+	}
+	var probe probeData
+	err = json.Unmarshal([]byte(jsonOutput), &probe)
+	if err != nil {
+		return nil, err
+	}
+	totalDuration, err := strconv.ParseFloat(probe.Format.Duration, 64)
+	if err != nil {
+		return nil, err
+	}
+
+	var ss string
+	if strings.HasSuffix(d.VideoThumbPos, "%") {
+		percentage, err := strconv.ParseFloat(strings.TrimSuffix(d.VideoThumbPos, "%"), 64)
+		if err != nil {
+			return nil, err
+		}
+		ss = fmt.Sprintf("%f", totalDuration*percentage/100)
+	} else {
+		val, err := strconv.ParseFloat(d.VideoThumbPos, 64)
+		if err != nil {
+			return nil, err
+		}
+		// If the value is greater than the total duration, use the total duration
+		if val > totalDuration {
+			ss = fmt.Sprintf("%f", totalDuration)
+		} else {
+			ss = d.VideoThumbPos
+		}
+	}
+
+	// Run ffmpeg to get the snapshot
 	srcBuf := bytes.NewBuffer(nil)
-	stream := ffmpeg.Input(videoPath).
-		Filter("select", ffmpeg.Args{fmt.Sprintf("gte(n,%d)", frameNum)}).
+	// If the remaining time from the seek point to the end of the video is less
+	// than the duration of a single frame, ffmpeg cannot extract any frames
+	// within the specified range and will exit with an error.
+	// The "noaccurate_seek" option prevents this error and would also speed up
+	// the seek process.
+	stream := ffmpeg.Input(videoPath, ffmpeg.KwArgs{"ss": ss, "noaccurate_seek": ""}).
 		Output("pipe:", ffmpeg.KwArgs{"vframes": 1, "format": "image2", "vcodec": "mjpeg"}).
 		GlobalArgs("-loglevel", "error").Silent(true).
 		WithOutput(srcBuf, os.Stdout)
@@ -77,7 +127,7 @@ func (d *Local) getThumb(file model.Obj) (*bytes.Buffer, *string, error) {
 	}
 	var srcBuf *bytes.Buffer
 	if utils.GetFileType(file.GetName()) == conf.VIDEO {
-		videoBuf, err := GetSnapshot(fullPath, 10)
+		videoBuf, err := d.GetSnapshot(fullPath)
 		if err != nil {
 			return nil, nil, err
 		}