ffmpeg: set muxer packet duration based on framerate only for CFR

a set ost->frame_rate does not imply CFR in ffmpeg

The changed fate tests had all wrong packet durations
(like 1/1000 or 1/90000)

There might be more cases in which is_cfr could be set

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

1 files changed, 2 insertions, 1 deletions

diff --git a/ffmpeg.c b/ffmpeg.c
index 7f3c426e09..ae78270023 100644
--- a/ffmpeg.c
+++ b/ffmpeg.c
@@ -672,7 +672,7 @@ static void write_frame(AVFormatContext *s, AVPacket *pkt, OutputStream *ost)
                 ost->error[i] = -1;
         }
 
-        if (ost->frame_rate.num) {
+        if (ost->frame_rate.num && ost->is_cfr) {
             pkt->duration = av_rescale_q(1, av_inv_q(ost->frame_rate),
                                          ost->st->time_base);
         }
@@ -1005,6 +1005,7 @@ static void do_video_out(AVFormatContext *s,
                 format_video_sync = VSYNC_VSCFR;
             }
         }
+        ost->is_cfr = (format_video_sync == VSYNC_CFR || format_video_sync == VSYNC_VSCFR);
 
         if (delta0 < 0 &&
             delta > 0 &&