avfilter/vf_fade: simplify code to use pts timebase for time check

Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

libavfilter/vf_fade.c

@@ -62,6 +62,7 @@ typedef struct FadeContext {
     int alpha;
     int is_planar;
     uint64_t start_time, duration;
+    uint64_t start_time_pts, duration_pts;
     enum {VF_FADE_WAITING=0, VF_FADE_FADING, VF_FADE_DONE} fade_state;
     uint8_t color_rgba[4];  ///< fade color
     int black_fade;         ///< if color_rgba is black
@@ -422,6 +423,11 @@ static int config_props(AVFilterLink *inlink)
     s->is_rgb = pixdesc->flags & AV_PIX_FMT_FLAG_RGB;
     s->is_packed_rgb = !s->is_planar && s->is_rgb;
 
+    if (s->duration)
+        s->duration_pts = av_rescale_q(s->duration, AV_TIME_BASE_Q, inlink->time_base);
+    if (s->start_time)
+        s->start_time_pts = av_rescale_q(s->start_time, AV_TIME_BASE_Q, inlink->time_base);
+
     /* use CCIR601/709 black level for studio-level pixel non-alpha components */
     s->black_level =
             ff_fmt_is_in(inlink->format, studio_level_pix_fmts) && !s->alpha ? 16 * (1 << (s->depth - 8)): 0;
@@ -440,29 +446,28 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 {
     AVFilterContext *ctx = inlink->dst;
     FadeContext *s       = ctx->priv;
-    double frame_timestamp = frame->pts == AV_NOPTS_VALUE ? -1 : frame->pts * av_q2d(inlink->time_base);
 
     // Calculate Fade assuming this is a Fade In
     if (s->fade_state == VF_FADE_WAITING) {
         s->factor=0;
-        if (frame_timestamp >= s->start_time/(double)AV_TIME_BASE
+        if (frame->pts >= s->start_time_pts
             && inlink->frame_count_out >= s->start_frame) {
             // Time to start fading
             s->fade_state = VF_FADE_FADING;
 
             // Save start time in case we are starting based on frames and fading based on time
-            if (s->start_time == 0 && s->start_frame != 0) {
-                s->start_time = frame_timestamp*(double)AV_TIME_BASE;
+            if (s->start_time_pts == 0 && s->start_frame != 0) {
+                s->start_time_pts = frame->pts;
             }
 
             // Save start frame in case we are starting based on time and fading based on frames
-            if (s->start_time != 0 && s->start_frame == 0) {
+            if (s->start_time_pts != 0 && s->start_frame == 0) {
                 s->start_frame = inlink->frame_count_out;
             }
         }
     }
     if (s->fade_state == VF_FADE_FADING) {
-        if (s->duration == 0) {
+        if (s->duration_pts == 0) {
             // Fading based on frame count
             s->factor = (inlink->frame_count_out - s->start_frame) * s->fade_per_frame;
             if (inlink->frame_count_out > s->start_frame + s->nb_frames) {
@@ -471,10 +476,8 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *frame)
 
         } else {
             // Fading based on duration
-            s->factor = (frame_timestamp - s->start_time/(double)AV_TIME_BASE)
-                            * (float) UINT16_MAX / (s->duration/(double)AV_TIME_BASE);
-            if (frame_timestamp > s->start_time/(double)AV_TIME_BASE
-                                  + s->duration/(double)AV_TIME_BASE) {
+            s->factor = (frame->pts - s->start_time_pts) * UINT16_MAX / s->duration_pts;
+            if (frame->pts > s->start_time_pts + s->duration_pts) {
                 s->fade_state = VF_FADE_DONE;
             }
         }