video: don't overwrite demuxer FPS value

If the --fps option was given (MPOpts->force_fps), the demuxer FPS value
was overwritten with the forced value. This was fine, since the demuxer
value wasn't needed anymore. But with the recent changes not to write to
the demuxer stream headers, we don't want to do this anymore. So
maintain the (forced/updated) FPS value in dec_video->fps.

The removed code in loadfile.c is probably redundant, and an artifact
from past refactorings.

Note that sub.c will now always use the demuxer FPS value, instead of
the user override value. I think this is fine, because it used the
demuxer's video size values too. (And it's rare that these values are
used at all.)

mpvcore/player/command.c

@@ -1534,7 +1534,7 @@ static int mp_property_fps(m_option_t *prop, int action, void *arg,
 {
     if (!mpctx->d_video)
         return M_PROPERTY_UNAVAILABLE;
-    return m_property_float_ro(prop, action, arg, mpctx->d_video->header->video->fps);
+    return m_property_float_ro(prop, action, arg, mpctx->d_video->fps);
 }
 
 /// Video aspect (RO)

mpvcore/player/loadfile.c

@@ -691,9 +691,6 @@ bool mp_remove_track(struct MPContext *mpctx, struct track *track)
 
 static void open_subtitles_from_options(struct MPContext *mpctx)
 {
-    // after reading video params we should load subtitles because
-    // we know fps so now we can adjust subtitle time to ~6 seconds AST
-    // check .sub
     if (mpctx->opts->sub_name) {
         for (int i = 0; mpctx->opts->sub_name[i] != NULL; ++i)
             mp_add_subtitles(mpctx, mpctx->opts->sub_name[i]);
@@ -1180,13 +1177,6 @@ goto_reopen_demuxer: ;
     reinit_audio_chain(mpctx);
     reinit_subs(mpctx);
 
-    //================ SETUP STREAMS ==========================
-
-    if (opts->force_fps && mpctx->d_video) {
-        mpctx->d_video->header->video->fps = opts->force_fps;
-        MP_INFO(mpctx, "FPS forced to be %5.3f.\n", mpctx->d_video->header->video->fps);
-    }
-
     //==================== START PLAYING =======================
 
     if (!mpctx->d_video && !mpctx->d_audio) {

mpvcore/player/video.c

@@ -48,7 +48,7 @@ void update_fps(struct MPContext *mpctx)
 #if HAVE_ENCODING
     struct dec_video *d_video = mpctx->d_video;
     if (mpctx->encode_lavc_ctx && d_video)
-        encode_lavc_set_video_fps(mpctx->encode_lavc_ctx, d_video->header->video->fps);
+        encode_lavc_set_video_fps(mpctx->encode_lavc_ctx, d_video->fps);
 #endif
 }
 
@@ -99,14 +99,6 @@ int reinit_video_chain(struct MPContext *mpctx)
                sh->format,
                sh->video->disp_w, sh->video->disp_h,
                sh->video->fps);
-    if (opts->force_fps)
-        sh->video->fps = opts->force_fps;
-    update_fps(mpctx);
-
-    if (!sh->video->fps && !opts->force_fps && !opts->correct_pts) {
-        MP_ERR(mpctx, "FPS not specified in the "
-               "header or invalid, use the -fps option.\n");
-    }
 
     double ar = -1.0;
     //================== Init VIDEO (codec & libvo) ==========================
@@ -129,6 +121,7 @@ int reinit_video_chain(struct MPContext *mpctx)
     d_video->last_pts = MP_NOPTS_VALUE;
     d_video->opts = mpctx->opts;
     d_video->header = sh;
+    d_video->fps = sh->video->fps;
     mpctx->initialized_flags |= INITIALIZED_VCODEC;
 
     vo_control(mpctx->video_out, VOCTRL_GET_HWDEC_INFO, &d_video->hwdec_info);
@@ -158,6 +151,16 @@ int reinit_video_chain(struct MPContext *mpctx)
     vo_seek_reset(mpctx->video_out);
     reset_subtitles(mpctx);
 
+    if (opts->force_fps) {
+        d_video->fps = opts->force_fps;
+        MP_INFO(mpctx, "FPS forced to be %5.3f.\n", d_video->fps);
+    }
+    if (!sh->video->fps && !opts->force_fps && !opts->correct_pts) {
+        MP_ERR(mpctx, "FPS not specified in the "
+               "header or invalid, use the -fps option.\n");
+    }
+    update_fps(mpctx);
+
     return 1;
 
 err_out:
@@ -247,7 +250,7 @@ static int check_framedrop(struct MPContext *mpctx, double frame_time)
     {
         float delay = opts->playback_speed * ao_get_delay(mpctx->ao);
         float d = delay - mpctx->delay;
-        float fps = mpctx->d_video->header->video->fps;
+        float fps = mpctx->d_video->fps;
         if (frame_time < 0)
             frame_time = fps > 0 ? 1.0 / fps : 0;
         // we should avoid dropping too many frames in sequence unless we
@@ -266,7 +269,6 @@ 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;
-    sh_video_t *sh_video = d_video->header->video;
     demuxer_t *demuxer = d_video->header->demuxer;
     float pts1 = d_video->last_pts;
 
@@ -277,7 +279,7 @@ static struct demux_packet *video_read_frame(struct MPContext *mpctx)
     if (pkt->pts != MP_NOPTS_VALUE)
         d_video->last_pts = pkt->pts;
 
-    float frame_time = sh_video->fps > 0 ? 1.0f / sh_video->fps : 0;
+    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) {
@@ -287,10 +289,10 @@ static struct demux_packet *video_read_frame(struct MPContext *mpctx)
         if (d >= 0) {
             if (demuxer->type == DEMUXER_TYPE_TV) {
                 if (d > 0)
-                    sh_video->fps = 1.0f / d;
+                    d_video->fps = 1.0f / d;
                 frame_time = d;
             } else {
-                if ((int)sh_video->fps <= 1)
+                if ((int)d_video->fps <= 1)
                     frame_time = d;
             }
         }

video/decode/dec_video.h

@@ -57,7 +57,7 @@ struct dec_video {
 
     float stream_aspect;  // aspect ratio in media headers (DVD IFO files)
     int i_bps;            // == bitrate  (compressed bytes/sec)
-
+    float fps;            // FPS from demuxer or from user override
     float initial_decoder_aspect;
 };