fix: ensure imageOverrides passes when empty

This commit ensures that the software functions correctly when imageOverrides
is empty. It also updates the description of the `aiRunnerImageOverrides` command
line flag.

cmd/livepeer/livepeer.go

@@ -162,7 +162,8 @@ func parseLivepeerConfig() starter.LivepeerConfig {
 	cfg.AIModels = flag.String("aiModels", *cfg.AIModels, "Set models (pipeline:model_id) for AI worker to load upon initialization")
 	cfg.AIModelsDir = flag.String("aiModelsDir", *cfg.AIModelsDir, "Set directory where AI model weights are stored")
 	cfg.AIRunnerImage = flag.String("aiRunnerImage", *cfg.AIRunnerImage, "[Deprecated] Specify the base Docker image for the AI runner. Example: livepeer/ai-runner:0.0.1. Use -aiRunnerImageOverrides instead.")
-	cfg.AIRunnerImageOverrides = flag.String("aiRunnerImageOverrides", *cfg.AIRunnerImageOverrides, `Specify overrides for the Docker images used by the AI runner. Example: '{"segment-anything-2": "livepeer/ai-runner:segment-anything-2-v1.0", "another-pipeline": "livepeer/ai-runner:another-pipeline-v1.0"}'`)
+	cfg.AIRunnerImageOverrides = flag.String("aiRunnerImageOverrides", *cfg.AIRunnerImageOverrides, `Specify overrides for the Docker images used by the AI runner. Example: '{"default": "livepeer/ai-runner:v1.0", "batch": {"text-to-speech": "livepeer/ai-runner:text-to-speech-v1.0"}, "live": {"another-pipeline": "livepeer/ai-runner:another-pipeline-v1.0"}}'`)
+
 	// Live AI:
 	cfg.MediaMTXApiPassword = flag.String("mediaMTXApiPassword", "", "HTTP basic auth password for MediaMTX API requests")
 	cfg.LiveAITrickleHostForRunner = flag.String("liveAITrickleHostForRunner", "", "Trickle Host used by AI Runner; It's used to overwrite the publicly available Trickle Host")

cmd/livepeer/starter/starter.go

@@ -1216,9 +1216,11 @@ func StartLivepeer(ctx context.Context, cfg LivepeerConfig) {
 
 		// Retrieve image overrides from the config.
 		var imageOverrides worker.ImageOverrides
-		if err := json.Unmarshal([]byte(*cfg.AIRunnerImageOverrides), &imageOverrides); err != nil {
-			glog.Errorf("Error unmarshaling image overrides: %v", err)
-			return
+		if *cfg.AIRunnerImageOverrides != "" {
+			if err := json.Unmarshal([]byte(*cfg.AIRunnerImageOverrides), &imageOverrides); err != nil {
+				glog.Errorf("Error unmarshaling image overrides: %v", err)
+				return
+			}
 		}
 
 		// Backwards compatibility for deprecated flags.