diff --git a/transcoder/README.md b/transcoder/README.md
index 36d5e0d5..11733201 100644
--- a/transcoder/README.md
+++ b/transcoder/README.md
@@ -22,6 +22,10 @@ Projects using gocoder:
 - [Blee](https://github.com/Arthi-chaud/Blee)
 - Add your own?
 
+## How does this work?
+
+I did a blog post explaining the core idea, you can find it at [zoriya.dev/blogs/transcoder](https://zoriya.dev/blogs/transcoder).
+
 ## TODO:
 - Add a swagger
 - Add configurable JWT authorization (v5 of kyoo)
diff --git a/transcoder/main.go b/transcoder/main.go
index da81cff4..68557a59 100644
--- a/transcoder/main.go
+++ b/transcoder/main.go
@@ -1,7 +1,6 @@
 package main
 
 import (
-	"fmt"
 	"net/http"
 	"strconv"
 
@@ -213,7 +212,10 @@ func (h *Handler) GetAttachment(c echo.Context) error {
 		return err
 	}
 
-	ret := fmt.Sprintf("%s/%s/att/%s", src.Settings.Metadata, sha, name)
+	ret, err := h.metadata.GetAttachmentPath(sha, false, name)
+	if err != nil {
+		return err
+	}
 	return c.File(ret)
 }
 
@@ -232,7 +234,10 @@ func (h *Handler) GetSubtitle(c echo.Context) error {
 		return err
 	}
 
-	ret := fmt.Sprintf("%s/%s/sub/%s", src.Settings.Metadata, sha, name)
+	ret, err := h.metadata.GetAttachmentPath(sha, true, name)
+	if err != nil {
+		return err
+	}
 	return c.File(ret)
 }
 
diff --git a/transcoder/src/extract.go b/transcoder/src/extract.go
index 6fcc7f4a..1181c6cb 100644
--- a/transcoder/src/extract.go
+++ b/transcoder/src/extract.go
@@ -7,8 +7,6 @@ import (
 	"os/exec"
 )
 
-var extracted = NewCMap[string, <-chan struct{}]()
-
 const ExtractVersion = 1
 
 func (s *MetadataService) ExtractSubs(info *MediaInfo) (interface{}, error) {
@@ -25,6 +23,18 @@ func (s *MetadataService) ExtractSubs(info *MediaInfo) (interface{}, error) {
 	return set(nil, err)
 }
 
+func (s *MetadataService) GetAttachmentPath(sha string, is_sub bool, name string) (string, error) {
+	_, err := s.extractLock.WaitFor(sha)
+	if err != nil {
+		return "", err
+	}
+	dir := "att"
+	if is_sub {
+		dir = "sub"
+	}
+	return fmt.Sprintf("%s/%s/%s/%s", Settings.Metadata, sha, dir, name), nil
+}
+
 func extractSubs(info *MediaInfo) error {
 	defer printExecTime("extraction of %s", info.Path)()
 
diff --git a/transcoder/src/runlock.go b/transcoder/src/runlock.go
index a971815e..f1f33c5f 100644
--- a/transcoder/src/runlock.go
+++ b/transcoder/src/runlock.go
@@ -61,3 +61,21 @@ func (r *RunLock[K, V]) Start(key K) (func() (V, error), func(val V, err error)
 		return val, err
 	}
 }
+
+func (r *RunLock[K, V]) WaitFor(key K) (V, error) {
+	r.lock.Lock()
+	task, ok := r.running[key]
+
+	if !ok {
+		r.lock.Unlock()
+		var val V
+		return val, nil
+	}
+
+	ret := make(chan Result[V])
+	task.listeners = append(task.listeners, ret)
+
+	r.lock.Unlock()
+	res := <-ret
+	return res.ok, res.err
+}
diff --git a/transcoder/src/thumbnails.go b/transcoder/src/thumbnails.go
index 31dcfc5a..97f8887d 100644
--- a/transcoder/src/thumbnails.go
+++ b/transcoder/src/thumbnails.go
@@ -27,8 +27,6 @@ type Thumbnail struct {
 	path  string
 }
 
-var thumbnails = NewCMap[string, *Thumbnail]()
-
 const ThumbsVersion = 1
 
 func getThumbGlob(sha string) string {