ffmpeg: use AVFrame.duration instead of AVFrame.pkt_duration

fftools/ffmpeg.c

@@ -1115,8 +1115,8 @@ static void do_video_out(OutputFile *of,
         (nb_filtergraphs == 0 || !filtergraphs[0]->graph_desc) &&
         next_picture &&
         ist &&
-        lrintf(next_picture->pkt_duration * av_q2d(ist->st->time_base) / av_q2d(enc->time_base)) > 0) {
-        duration = lrintf(next_picture->pkt_duration * av_q2d(ist->st->time_base) / av_q2d(enc->time_base));
+        lrintf(next_picture->duration * av_q2d(ist->st->time_base) / av_q2d(enc->time_base)) > 0) {
+        duration = lrintf(next_picture->duration * av_q2d(ist->st->time_base) / av_q2d(enc->time_base));
     }
 
     if (!next_picture) {
@@ -2237,7 +2237,7 @@ static int decode_video(InputStream *ist, AVPacket *pkt, int *got_output, int64_
     ist->hwaccel_retrieved_pix_fmt = decoded_frame->format;
 
     best_effort_timestamp= decoded_frame->best_effort_timestamp;
-    *duration_pts = decoded_frame->pkt_duration;
+    *duration_pts = decoded_frame->duration;
 
     if (ist->framerate.num)
         best_effort_timestamp = ist->cfr_next_pts++;