transcode: try FI32 as intermediate format

Some formats can only be converted to FI32, and then
a FI32->FL32 converter can be used.

modules/stream_out/transcode/audio.c

@@ -112,11 +112,28 @@ static int transcode_audio_filter_chain_build( sout_stream_t *p_stream, filter_c
         current.audio.i_format = VLC_CODEC_FL32;
         aout_FormatPrepare( &current.audio );
 
+        if( !filter_chain_AppendFilter( p_chain, NULL, NULL, NULL, &current ) )
+        {
+            /* If that fails, try going through fi32 */
+            current.i_codec =
+                current.audio.i_format = VLC_CODEC_FI32;
+            aout_FormatPrepare( &current.audio );
+
+            if( !filter_chain_AppendFilter( p_chain, NULL, NULL, NULL, &current ) )
+            {
+                msg_Err( p_stream, "Failed to find conversion filter to fi32" );
+                return VLC_EGENERIC;
+            }
+            current = *filter_chain_GetFmtOut( p_chain );
+            current.i_codec =
+                current.audio.i_format = VLC_CODEC_FL32;
+            aout_FormatPrepare( &current.audio );
             if( !filter_chain_AppendFilter( p_chain, NULL, NULL, NULL, &current ) )
             {
                 msg_Err( p_stream, "Failed to find conversion filter to fl32" );
                 return VLC_EGENERIC;
             }
+        }
         current = *filter_chain_GetFmtOut( p_chain );
     }