func: static int transcode_step() OutputStream * ost ; InputStream * ist ; int ret ; ost = choose_output ( ); static OutputStream *choose_output() int i ; int64_t opts_min = 9223372036854775807L ; OutputStream * ost_min = ( ( void * ) 0 ) ; for (i = 0; i < nb_output_streams; i++) OutputStream * ost = output_streams [ i ] ; int64_t opts = av_rescale_q ( ost -> st -> cur_dts , ost -> st -> time_base , ( ( AVRational ) ( 1 ) , ( 1000000 ) ) ) if ( ! ost -> unavailable && ! ost -> finished && opts < opts_min )  opts_min = opts; ost_min = ost; return ost_min ; if ( ! ost )  if ( ost -> filter )  if ( ( ret = transcode_from_filter ( ost -> filter -> graph , & ist ) ) < 0 )  static int transcode_from_filter(FilterGraph *graph,InputStream **best_ist) int ret ; ret = avfilter_graph_request_oldest ( graph -> graph ); if ( ret >= 0 )  return reap_filters ( ) ; static int reap_filters() int i ; for (i = 0; i < nb_output_streams; i++) OutputStream * ost = output_streams [ i ] ; if ( ! ost -> filter )  if ( ! ost -> filtered_frame && ! ( ost -> filtered_frame = avcodec_alloc_frame ( ) ) )  return - 12 ; return 0 ; if ( ret == - ( ( int ) ( ( 'E' | 'O' << 8 | 'F' << 16 ) | ( ( unsigned int ) 32 ) << 24 ) ) )  ret = reap_filters ( ); static int reap_filters() int i ; OutputStream * ost = output_streams [ i ] ; if ( ! ost -> filter )  if ( ! ost -> filtered_frame && ! ( ost -> filtered_frame = avcodec_alloc_frame ( ) ) )  return - 12 ; return 0 ; return ret ; if ( ret != - 11 )  return ret ; return 0 ; if ( ! ist )  ist = input_streams [ ost -> source_index ]; ret = process_input ( ist -> file_index ); static int process_input(int file_index) InputFile * ifile = input_files [ file_index ] ; int ret ; ret = get_input_packet ( ifile , & pkt ); static int get_input_packet(InputFile *f,AVPacket *pkt) if ( nb_input_files > 1 )  return get_input_packet_mt ( f , pkt ) ; static int get_input_packet_mt(InputFile *f,AVPacket *pkt) pthread_mutex_unlock ( & f -> fifo_lock ); 