fftools/ffmpeg_filter: log an information message about filter graph reconfigurations

Filter graph reconfigurations can cause nontrivial issues, e.g. PTS
discontinuities, so it is better to warn the user about them.

Signed-off-by: Marton Balint <cus@passwd.hu>

fftools/ffmpeg_filter.c

@@ -2598,43 +2598,57 @@ static int send_eof(FilterGraphThread *fgt, InputFilter *ifilter,
     return 0;
 }
 
+enum ReinitReason {
+    VIDEO_CHANGED   = (1 << 0),
+    AUDIO_CHANGED   = (1 << 1),
+    MATRIX_CHANGED  = (1 << 2),
+    HWACCEL_CHANGED = (1 << 3)
+};
+
+static const char *unknown_if_null(const char *str)
+{
+    return str ? str : "unknown";
+}
+
 static int send_frame(FilterGraph *fg, FilterGraphThread *fgt,
                       InputFilter *ifilter, AVFrame *frame)
 {
     InputFilterPriv *ifp = ifp_from_ifilter(ifilter);
     FrameData       *fd;
     AVFrameSideData *sd;
-    int need_reinit, ret;
+    int need_reinit = 0, ret;
 
     /* determine if the parameters for this input changed */
-    need_reinit = ifp->format != frame->format;
-
     switch (ifp->type) {
     case AVMEDIA_TYPE_AUDIO:
-        need_reinit |= ifp->sample_rate    != frame->sample_rate ||
-                       av_channel_layout_compare(&ifp->ch_layout, &frame->ch_layout);
+        if (ifp->format      != frame->format ||
+            ifp->sample_rate != frame->sample_rate ||
+            av_channel_layout_compare(&ifp->ch_layout, &frame->ch_layout))
+            need_reinit |= AUDIO_CHANGED;
         break;
     case AVMEDIA_TYPE_VIDEO:
-        need_reinit |= ifp->width  != frame->width ||
-                       ifp->height != frame->height ||
-                       ifp->color_space != frame->colorspace ||
-                       ifp->color_range != frame->color_range;
+        if (ifp->format != frame->format ||
+            ifp->width  != frame->width ||
+            ifp->height != frame->height ||
+            ifp->color_space != frame->colorspace ||
+            ifp->color_range != frame->color_range)
+            need_reinit |= VIDEO_CHANGED;
         break;
     }
 
     if (sd = av_frame_get_side_data(frame, AV_FRAME_DATA_DISPLAYMATRIX)) {
         if (!ifp->displaymatrix_present ||
             memcmp(sd->data, ifp->displaymatrix, sizeof(ifp->displaymatrix)))
-            need_reinit = 1;
+            need_reinit |= MATRIX_CHANGED;
     } else if (ifp->displaymatrix_present)
-        need_reinit = 1;
+        need_reinit |= MATRIX_CHANGED;
 
     if (!ifp->ist->reinit_filters && fgt->graph)
         need_reinit = 0;
 
     if (!!ifp->hw_frames_ctx != !!frame->hw_frames_ctx ||
         (ifp->hw_frames_ctx && ifp->hw_frames_ctx->data != frame->hw_frames_ctx->data))
-        need_reinit = 1;
+        need_reinit |= HWACCEL_CHANGED;
 
     if (need_reinit) {
         ret = ifilter_parameters_from_frame(ifilter, frame);
@@ -2664,6 +2678,32 @@ static int send_frame(FilterGraph *fg, FilterGraphThread *fgt,
         if (ret < 0)
             return ret;
 
+        if (fgt->graph) {
+            AVBPrint reason;
+            av_bprint_init(&reason, 0, AV_BPRINT_SIZE_AUTOMATIC);
+            if (need_reinit & AUDIO_CHANGED) {
+                const char *sample_format_name = av_get_sample_fmt_name(frame->format);
+                av_bprintf(&reason, "audio parameters changed to %d Hz, ", frame->sample_rate);
+                av_channel_layout_describe_bprint(&frame->ch_layout, &reason);
+                av_bprintf(&reason, ", %s, ", unknown_if_null(sample_format_name));
+            }
+            if (need_reinit & VIDEO_CHANGED) {
+                const char *pixel_format_name = av_get_pix_fmt_name(frame->format);
+                const char *color_space_name = av_color_space_name(frame->colorspace);
+                const char *color_range_name = av_color_range_name(frame->color_range);
+                av_bprintf(&reason, "video parameters changed to %s(%s, %s), %dx%d, ",
+                        unknown_if_null(pixel_format_name), unknown_if_null(color_range_name),
+                        unknown_if_null(color_space_name), frame->width, frame->height);
+            }
+            if (need_reinit & MATRIX_CHANGED)
+                av_bprintf(&reason, "display matrix changed, ");
+            if (need_reinit & HWACCEL_CHANGED)
+                av_bprintf(&reason, "hwaccel changed, ");
+            if (reason.len > 1)
+                reason.str[reason.len - 2] = '\0'; // remove last comma
+            av_log(fg, AV_LOG_INFO, "Reconfiguring filter graph%s%s\n", reason.len ? " because " : "", reason.str);
+        }
+
         ret = configure_filtergraph(fg, fgt);
         if (ret < 0) {
             av_log(fg, AV_LOG_ERROR, "Error reinitializing filters!\n");