video: don't drop last frame when deinterlacing with yadif

Or in other words, add support for properly draining remaining frames
from video filters. vf_yadif is buffering at least one frame, and the
buffered frame was not retrieved on EOF.

For most filters, ignore this for now, and just adjust them to the
changed semantics of filter_ext. But for vf_lavfi (used by vf_yadif),
real support is implemented. libavfilter handles this simply by passing
a NULL frame to av_buffersrc_add_frame(), so we just have to make
mp_to_av() handle NULL arguments.

In load_next_vo_frame(), we first try to output a frame buffered in the
VO, then the filter, and then (if EOF is reached and there's still no
new frame) the VO again, with draining enabled. I guess this was
implemented slightly incorrectly before, because the filter chain still
could have had remaining output frames.

7 files changed, 32 insertions, 6 deletions

diff --git a/video/filter/vf.c b/video/filter/vf.c
index 0d8f239721..021a0e21ae 100644
--- a/video/filter/vf.c
+++ b/video/filter/vf.c
@@ -363,14 +363,17 @@ static struct mp_image *vf_dequeue_output_frame(struct vf_instance *vf)
 static int vf_do_filter(struct vf_instance *vf, struct mp_image *img)
 {
     assert(vf->fmt_in.imgfmt);
-    vf_fix_img_params(img, &vf->fmt_in);
+    if (img)
+        vf_fix_img_params(img, &vf->fmt_in);
 
     if (vf->filter_ext) {
         return vf->filter_ext(vf, img);
     } else {
-        if (vf->filter)
-            img = vf->filter(vf, img);
-        vf_add_output_frame(vf, img);
+        if (img) {
+            if (vf->filter)
+                img = vf->filter(vf, img);
+            vf_add_output_frame(vf, img);
+        }
         return 0;
     }
 }
@@ -379,6 +382,7 @@ static int vf_do_filter(struct vf_instance *vf, struct mp_image *img)
 // Return >= 0 on success, < 0 on failure (even if output frames were produced)
 int vf_filter_frame(struct vf_chain *c, struct mp_image *img)
 {
+    assert(img);
     if (c->initialized < 1) {
         talloc_free(img);
         return -1;
@@ -387,13 +391,19 @@ int vf_filter_frame(struct vf_chain *c, struct mp_image *img)
 }
 
 // Output the next queued image (if any) from the full filter chain.
-struct mp_image *vf_output_queued_frame(struct vf_chain *c)
+//  eof: if set, assume there's no more input i.e. vf_filter_frame() will
+//       not be called (until reset) - flush all internally delayed frames
+struct mp_image *vf_output_queued_frame(struct vf_chain *c, bool eof)
 {
     if (c->initialized < 1)
         return NULL;
     while (1) {
         struct vf_instance *last = NULL;
         for (struct vf_instance * cur = c->first; cur; cur = cur->next) {
+            // Flush remaining frames on EOF, but do that only if the previous
+            // filters have been flushed (i.e. they have no more output).
+            if (eof && !last)
+                vf_do_filter(cur, NULL);
             if (cur->num_out_queued)
                 last = cur;
         }
diff --git a/video/filter/vf.h b/video/filter/vf.h
index d11c6de575..8e73c69256 100644
--- a/video/filter/vf.h
+++ b/video/filter/vf.h
@@ -70,6 +70,9 @@ typedef struct vf_instance {
     // Like filter(), but can return an error code ( >= 0 means success). This
     // callback is also more practical when the filter can return multiple
     // output images. Use vf_add_output_frame() to queue output frames.
+    // Warning: this is called with mpi==NULL if there is no more input at
+    //          all (i.e. the video has reached end of file condition). This
+    //          can be used to output delayed or otherwise remaining images.
     int (*filter_ext)(struct vf_instance *vf, struct mp_image *mpi);
 
     void (*uninit)(struct vf_instance *vf);
@@ -133,7 +136,7 @@ int vf_reconfig(struct vf_chain *c, const struct mp_image_params *params);
 int vf_control_any(struct vf_chain *c, int cmd, void *arg);
 int vf_control_by_label(struct vf_chain *c, int cmd, void *arg, bstr label);
 int vf_filter_frame(struct vf_chain *c, struct mp_image *img);
-struct mp_image *vf_output_queued_frame(struct vf_chain *c);
+struct mp_image *vf_output_queued_frame(struct vf_chain *c, bool eof);
 void vf_seek_reset(struct vf_chain *c);
 struct vf_instance *vf_append_filter(struct vf_chain *c, const char *name,
                                      char **args);
diff --git a/video/filter/vf_dlopen.c b/video/filter/vf_dlopen.c
index 4eefec150c..70c2c6cf24 100644
--- a/video/filter/vf_dlopen.c
+++ b/video/filter/vf_dlopen.c
@@ -225,6 +225,9 @@ static int filter(struct vf_instance *vf, struct mp_image *mpi)
 {
     int i, k;
 
+    if (!mpi)
+        return 0;
+
     set_imgprop(&vf->priv->filter.inpic, mpi);
     if (mpi->qscale) {
         if (mpi->qscale_type != 0) {
diff --git a/video/filter/vf_lavfi.c b/video/filter/vf_lavfi.c
index b100763e05..8e446cec1d 100644
--- a/video/filter/vf_lavfi.c
+++ b/video/filter/vf_lavfi.c
@@ -251,6 +251,8 @@ static int query_format(struct vf_instance *vf, unsigned int fmt)
 static AVFrame *mp_to_av(struct vf_instance *vf, struct mp_image *img)
 {
     struct vf_priv_s *p = vf->priv;
+    if (!img)
+        return NULL;
     uint64_t pts = img->pts == MP_NOPTS_VALUE ?
                    AV_NOPTS_VALUE : img->pts * av_q2d(av_inv_q(p->timebase_in));
     AVFrame *frame = mp_image_to_av_frame_and_unref(img);
diff --git a/video/filter/vf_softpulldown.c b/video/filter/vf_softpulldown.c
index eeb2f1c863..afa6bf31f0 100644
--- a/video/filter/vf_softpulldown.c
+++ b/video/filter/vf_softpulldown.c
@@ -54,6 +54,9 @@ static int filter(struct vf_instance *vf, struct mp_image *mpi)
         int state = vf->priv->state;
         struct vf_priv_s *p = vf->priv;
 
+        if (!mpi)
+            return 0;
+
         if (!p->buffer || p->buffer->w != mpi->w || p->buffer->h != mpi->h ||
             p->buffer->imgfmt != mpi->imgfmt)
         {
diff --git a/video/filter/vf_vapoursynth.c b/video/filter/vf_vapoursynth.c
index 313b66e26b..a6cf471583 100644
--- a/video/filter/vf_vapoursynth.c
+++ b/video/filter/vf_vapoursynth.c
@@ -180,6 +180,9 @@ static int filter_ext(struct vf_instance *vf, struct mp_image *mpi)
     if (!p->out_node)
         return -1;
 
+    if (!mpi)
+        return 0;
+
     // Try to get new frames until we get rid of the input mpi.
     pthread_mutex_lock(&p->lock);
     while (1) {
diff --git a/video/filter/vf_vavpp.c b/video/filter/vf_vavpp.c
index 9a797990eb..4b6322cbe2 100644
--- a/video/filter/vf_vavpp.c
+++ b/video/filter/vf_vavpp.c
@@ -222,6 +222,8 @@ static struct mp_image *upload(struct vf_instance *vf, struct mp_image *in)
 static int filter_ext(struct vf_instance *vf, struct mp_image *in)
 {
     struct vf_priv_s *p = vf->priv;
+    if (!in)
+        return 0;
     int rt_format = in->imgfmt == IMGFMT_VAAPI ? va_surface_rt_format(in)
                                                : VA_RT_FORMAT_YUV420;
     if (!p->pool || p->current_rt_format != rt_format) {