player: change semantics of --no-correct-pts

Before this commit, this mode estimated the frame time by subtracting
successive packet PTS values. This is complete non-sense for video
codecs which use reordering. The code compensated frame times for these
non-sense using the FPS value, but confused the rest of the player with
non-sense jumping around timestamps. So, all in all this mode is not
very useful.

Repurpose this mode for fixed frame rate playback. This gives almost the
same behavior as the old mode with forced framerate (--fps option). The
result is simpler and often more robust.

2 files changed, 8 insertions, 27 deletions

diff --git a/mpvcore/player/video.c b/mpvcore/player/video.c
index f858106750..362ee94c75 100644
--- a/mpvcore/player/video.c
+++ b/mpvcore/player/video.c
@@ -269,37 +269,19 @@ static int check_framedrop(struct MPContext *mpctx, double frame_time)
 static struct demux_packet *video_read_frame(struct MPContext *mpctx)
 {
     struct dec_video *d_video = mpctx->d_video;
-    demuxer_t *demuxer = d_video->header->demuxer;
-    float pts1 = d_video->last_pts;
-
+    double frame_time = 1.0f / (d_video->fps > 0 ? d_video->fps : 25);
     struct demux_packet *pkt = demux_read_packet(d_video->header);
     if (!pkt)
         return NULL; // EOF
 
-    if (pkt->pts != MP_NOPTS_VALUE)
-        d_video->last_pts = pkt->pts;
-
-    float frame_time = d_video->fps > 0 ? 1.0f / d_video->fps : 0;
-
-    // override frame_time for variable/unknown FPS formats:
-    if (!mpctx->opts->force_fps) {
-        double next_pts = demux_get_next_pts(d_video->header);
-        double d = next_pts == MP_NOPTS_VALUE ? d_video->last_pts - pts1
-                                              : next_pts - d_video->last_pts;
-        if (d >= 0) {
-            if (demuxer->type == DEMUXER_TYPE_TV) {
-                if (d > 0)
-                    d_video->fps = 1.0f / d;
-                frame_time = d;
-            } else {
-                if ((int)d_video->fps <= 1)
-                    frame_time = d;
-            }
-        }
+    if (d_video->last_pts == MP_NOPTS_VALUE) {
+        d_video->last_pts = pkt->pts == MP_NOPTS_VALUE ? 0 : pkt->pts;
+        d_video->pts = d_video->last_pts;
     }
 
-    d_video->pts = d_video->last_pts;
-    d_video->next_frame_time = frame_time;
+    double prev = d_video->pts;
+    d_video->pts = d_video->pts + frame_time;
+    d_video->last_pts = prev;
     return pkt;
 }
 
@@ -311,7 +293,7 @@ static double update_video_nocorrect_pts(struct MPContext *mpctx)
         // In nocorrect-pts mode there is no way to properly time these frames
         if (load_next_vo_frame(mpctx, false))
             break;
-        frame_time = d_video->next_frame_time;
+        frame_time = d_video->pts - d_video->last_pts;
         if (mpctx->restart_playback)
             frame_time = 0;
         struct demux_packet *pkt = video_read_frame(mpctx);
diff --git a/video/decode/dec_video.h b/video/decode/dec_video.h
index 9802e4c300..3856d12043 100644
--- a/video/decode/dec_video.h
+++ b/video/decode/dec_video.h
@@ -59,7 +59,6 @@ struct dec_video {
     float initial_decoder_aspect;
 
     // State used only by player/video.c
-    float next_frame_time;
     double last_pts;
 };