avformat/hlsenc: improve compute after_init_list_dur

fix ticket: 7305
vs->sequence - hls->start_sequence - vs->nb_entries is the
after_init_list_dur fragment numbers
fix the wrong compute way vs->sequence - vs->nb_entries

Signed-off-by: Steven Liu <lq@chinaffmpeg.org>

libavformat/hlsenc.c

@@ -2178,7 +2178,7 @@ static int hls_write_packet(AVFormatContext *s, AVPacket *pkt)
     if (vs->sequence - vs->nb_entries > hls->start_sequence && hls->init_time > 0) {
         /* reset end_pts, hls->recording_time at end of the init hls list */
         int init_list_dur = hls->init_time * vs->nb_entries * AV_TIME_BASE;
-        int after_init_list_dur = (vs->sequence - vs->nb_entries ) * hls->time * AV_TIME_BASE;
+        int after_init_list_dur = (vs->sequence - hls->start_sequence - vs->nb_entries ) * (hls->time * AV_TIME_BASE);
         hls->recording_time = hls->time * AV_TIME_BASE;
         end_pts = init_list_dur + after_init_list_dur ;
     }