feat: support S3 media processing pipeline

backend/app/jobs/media_process_job.go

@@ -114,7 +114,49 @@ func (j *MediaProcessWorker) Work(ctx context.Context, job *river.Job[args.Media
 				}
 			}
 		} else {
-			log.Warn("non-local provider, skipping ffmpeg processing")
+			tempDir, err := os.MkdirTemp("", "media-process-")
+			if err != nil {
+				log.Errorf("create temp dir failed: %v", err)
+				finalStatus = consts.MediaAssetStatusFailed
+			} else {
+				defer os.RemoveAll(tempDir)
+				ext := path.Ext(asset.ObjectKey)
+				inputFile := filepath.Join(tempDir, "source"+ext)
+				if err := j.storage.Download(ctx, asset.ObjectKey, inputFile); err != nil {
+					log.Errorf("download media file failed: %s, err=%v", asset.ObjectKey, err)
+					finalStatus = consts.MediaAssetStatusFailed
+				} else if _, err := exec.LookPath("ffmpeg"); err != nil {
+					log.Warn("ffmpeg not found, skipping real transcoding")
+				} else {
+					coverFile := filepath.Join(tempDir, "cover.jpg")
+					cmd := exec.CommandContext(
+						ctx,
+						"ffmpeg",
+						"-y",
+						"-i",
+						inputFile,
+						"-ss",
+						"00:00:00.000",
+						"-vframes",
+						"1",
+						"-vf",
+						"format=yuv420p",
+						"-update",
+						"1",
+						coverFile,
+					)
+					if out, err := cmd.CombinedOutput(); err != nil {
+						log.Errorf("ffmpeg failed: %s, output: %s", err, string(out))
+						finalStatus = consts.MediaAssetStatusFailed
+					} else {
+						log.Infof("Generated cover: %s", coverFile)
+						if err := j.registerCoverAsset(ctx, asset, coverFile); err != nil {
+							log.Errorf("register cover failed: %s", err)
+							finalStatus = consts.MediaAssetStatusFailed
+						}
+					}
+				}
+			}
 		}
 	}
 
@@ -175,21 +217,27 @@ func (j *MediaProcessWorker) registerCoverAsset(ctx context.Context, asset *mode
 	coverName := coverFilename(filename)
 	objectKey := buildObjectKey(tenant, hash, coverName)
 
-	// 本地存储将文件移动到目标 objectKey 位置，保持路径规范。
-	localPath := j.storage.Config.LocalPath
-	if localPath == "" {
-		localPath = "./storage"
-	}
-	dstPath := filepath.Join(localPath, filepath.FromSlash(objectKey))
-	if coverFile != dstPath {
-		if err := os.MkdirAll(filepath.Dir(dstPath), 0o755); err != nil {
-			return err
-		}
-		if _, err := os.Stat(dstPath); err == nil {
-			_ = os.Remove(coverFile)
-		} else if err := os.Rename(coverFile, dstPath); err != nil {
+	if strings.ToLower(asset.Provider) == "local" {
+		localPath := j.storage.Config.LocalPath
+		if localPath == "" {
+			localPath = "./storage"
+		}
+		dstPath := filepath.Join(localPath, filepath.FromSlash(objectKey))
+		if coverFile != dstPath {
+			if err := os.MkdirAll(filepath.Dir(dstPath), 0o755); err != nil {
+				return err
+			}
+			if _, err := os.Stat(dstPath); err == nil {
+				_ = os.Remove(coverFile)
+			} else if err := os.Rename(coverFile, dstPath); err != nil {
+				return err
+			}
+		}
+	} else {
+		if err := j.storage.PutObject(ctx, objectKey, coverFile, "image/jpeg"); err != nil {
 			return err
 		}
+		_ = os.Remove(coverFile)
 	}
 
 	coverAsset := &models.MediaAsset{