transcode: video: drain all filter chains sequentially until they're dry

Loop while there are pictures to encode.

- Start by filtering the first picture through each filter chain, and encode
the result.
- Then drain the first (non-null) filter chain and pass the result through
the other filter chain, and encode the result.
- Then drain the second (non-null) filter chain and pass the result through
the other filter chain, and encode the result.
- And so on, until there is no more filtered pictures to encode.

modules/stream_out/transcode/video.c

@@ -573,35 +573,24 @@ int transcode_video_process( sout_stream_t *p_stream, sout_stream_id_sys_t *id,
          * and then with NULL as many times as we need until they
          * stop outputting frames.
          */
-        for ( picture_t *p_in = p_pic; ; p_in = NULL /* drain second time */ )
+        for ( picture_t *p_in = p_pic; ; p_in = NULL /* keep draining */ )
         {
-            /* Run filter chain */
-            if( id->p_f_chain )
+            filter_chain_t * chains[] = { id->p_f_chain,
+                                          id->p_uf_chain,
+                                          id->p_final_conv_static };
+            for( size_t i=0; i<ARRAY_SIZE(chains); i++ )
             {
+                if( !chains[i] )
+                    continue;
                 if ( p_in )
-                    p_in = filter_chain_VideoFilter( id->p_f_chain, p_in );
+                    p_in = filter_chain_VideoFilter( chains[i], p_in );
                 else
-                    p_in = filter_chain_VideoDrain( id->p_f_chain );
+                    p_in = filter_chain_VideoDrain( chains[i] );
             }
 
             if( !p_in )
                 break;
 
-            for ( ;; p_in = NULL /* drain second time */ )
-            {
-                /* Run user specified filter chain */
-                filter_chain_t * secondary_chains[] = { id->p_uf_chain,
-                                                        id->p_final_conv_static };
-                for( size_t i=0; p_in && i<ARRAY_SIZE(secondary_chains); i++ )
-                {
-                    if( !secondary_chains[i] )
-                        continue;
-                    p_in = filter_chain_VideoFilter( secondary_chains[i], p_in );
-                }
-
-                if( !p_in )
-                    break;
-
                 /* Blend subpictures */
                 p_in = RenderSubpictures( id, p_in );
 
@@ -612,7 +601,6 @@ int transcode_video_process( sout_stream_t *p_stream, sout_stream_id_sys_t *id,
                         block_ChainAppend( out, p_encoded );
                     picture_Release( p_in );
                 }
-            }
         }
 
         if( b_eos )