Fix YouTube waiting: transcode verso RTMP e sync stato live.

Il relay non usa più copy (stream inactive su YouTube); PublisherSync
nel refresh overlay; activate solo quando lo stream YouTube è active.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/app/services/streams/youtube_relay.rb

@@ -19,14 +19,9 @@ module Streams
         intake = mediamtx_intake_url(session)
         output = "rtmp://a.rtmp.youtube.com/live2/#{session.stream_key}"
 
+        # YouTube richiede FLV H.264/AAC stabili; -c copy lascia spesso streamStatus=inactive.
         pid = Process.spawn(
-          "ffmpeg", "-nostdin", "-hide_banner", "-loglevel", "warning",
-          "-rw_timeout", "15000000",
-          "-i", intake,
-          "-c", "copy",
-          "-f", "flv",
-          output,
-          %i[out err] => log_path,
+          *youtube_ffmpeg_args(intake, output, log_path),
           pgroup: true
         )
         Process.detach(pid)
@@ -62,13 +57,33 @@ module Streams
 
         return if running?(session.id)
 
+        last_restart = redis.get(restart_debounce_key(session.id)).to_i
+        return if last_restart.positive? && (Time.now.to_i - last_restart) < 20
+
         start(session)
+        redis.set(restart_debounce_key(session.id), Time.now.to_i, ex: 300)
       rescue Error => e
         Rails.logger.warn("[YoutubeRelay] ensure_publishing session=#{session.id}: #{e.message}")
       end
 
       private
 
+      def youtube_ffmpeg_args(intake, output, log_path)
+        [
+          "ffmpeg", "-nostdin", "-hide_banner", "-loglevel", "warning",
+          "-fflags", "+genpts+discardcorrupt", "-use_wallclock_as_timestamps", "1",
+          "-rw_timeout", "15000000",
+          "-i", intake,
+          "-map", "0:v:0", "-map", "0:a:0",
+          "-c:v", "libx264", "-preset", "veryfast", "-tune", "zerolatency",
+          "-pix_fmt", "yuv420p", "-r", "30", "-g", "30", "-keyint_min", "30", "-sc_threshold", "0",
+          "-b:v", "4000k", "-maxrate", "4000k", "-bufsize", "8000k",
+          "-c:a", "aac", "-b:a", "128k", "-ar", "48000", "-ac", "1",
+          "-f", "flv", output,
+          %i[out err] => log_path
+        ]
+      end
+
       def schedule_youtube_activate(session)
         return if session.youtube_broadcast_id.blank?
 
@@ -88,6 +103,10 @@ module Streams
         @redis ||= Redis.new(url: ENV.fetch("REDIS_URL", "redis://localhost:6379/0"))
       end
 
+      def restart_debounce_key(session_id)
+        format("youtube_relay:debounce:%s", session_id)
+      end
+
       def store_pid(session_id, pid)
         redis.set(format(REDIS_KEY, session_id), pid, ex: 48.hours.to_i)
       end