[FFmpeg-devel,04/11] fftools/ffmpeg_filter: take fallback parameters from decoder, not demuxer

diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
index 983573b991..38569c60a4 100644
--- a/fftools/ffmpeg.c
+++ b/fftools/ffmpeg.c
@@ -769,24 +769,6 @@  static void print_report(int is_last_report, int64_t timer_start, int64_t cur_ti
     first_report = 0;
 }
 
-int ifilter_parameters_from_codecpar(InputFilter *ifilter, AVCodecParameters *par)
-{
-    int ret;
-
-    // We never got any input. Set a fake format, which will
-    // come from libavformat.
-    ifilter->format                 = par->format;
-    ifilter->sample_rate            = par->sample_rate;
-    ifilter->width                  = par->width;
-    ifilter->height                 = par->height;
-    ifilter->sample_aspect_ratio    = par->sample_aspect_ratio;
-    ret = av_channel_layout_copy(&ifilter->ch_layout, &par->ch_layout);
-    if (ret < 0)
-        return ret;
-
-    return 0;
-}
-
 static void check_decode_result(InputStream *ist, int *got_output, int ret)
 {
     if (*got_output || ret<0)
diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index ec4c580b91..525a00bfcb 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -791,7 +791,13 @@  void sub2video_update(InputStream *ist, int64_t heartbeat_pts, AVSubtitle *sub);
 int ifilter_send_frame(InputFilter *ifilter, AVFrame *frame, int keep_reference);
 int ifilter_send_eof(InputFilter *ifilter, int64_t pts, AVRational tb);
 
-int ifilter_parameters_from_codecpar(InputFilter *ifilter, AVCodecParameters *par);
+/**
+ * Set up fallback filtering parameters from a decoder context. They will only
+ * be used if no frames are ever sent on this input, otherwise the actual
+ * parameters are taken from the frame.
+ */
+int ifilter_parameters_from_dec(InputFilter *ifilter, const AVCodecContext *dec);
+
 int ifilter_has_all_input_formats(FilterGraph *fg);
 
 /**
diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c
index 6727193697..ad283356ba 100644
--- a/fftools/ffmpeg_demux.c
+++ b/fftools/ffmpeg_demux.c
@@ -586,10 +586,17 @@  void ist_output_add(InputStream *ist, OutputStream *ost)
 
 void ist_filter_add(InputStream *ist, InputFilter *ifilter, int is_simple)
 {
+    int ret;
+
     ist_use(ist, is_simple ? DECODING_FOR_OST : DECODING_FOR_FILTER);
 
     GROW_ARRAY(ist->filters, ist->nb_filters);
     ist->filters[ist->nb_filters - 1] = ifilter;
+
+    // initialize fallback parameters for filtering
+    ret = ifilter_parameters_from_dec(ifilter, ist->dec_ctx);
+    if (ret < 0)
+        report_and_exit(ret);
 }
 
 static const AVCodec *choose_decoder(const OptionsContext *o, AVFormatContext *s, AVStream *st,
diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index 8c408eb7c4..3fad38f782 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -58,6 +58,19 @@  typedef struct InputFilterPriv {
     AVRational time_base;
 
     AVFifo *frame_queue;
+
+    // fallback parameters to use when no input is ever sent
+    struct {
+        int                 format;
+
+        int                 width;
+        int                 height;
+        AVRational          sample_aspect_ratio;
+
+        int                 sample_rate;
+        AVChannelLayout     ch_layout;
+    } fallback;
+
 } InputFilterPriv;
 
 static InputFilterPriv *ifp_from_ifilter(InputFilter *ifilter)
@@ -225,6 +238,8 @@  static InputFilter *ifilter_alloc(FilterGraph *fg)
     ifilter->graph  = fg;
     ifilter->format = -1;
 
+    ifp->fallback.format = -1;
+
     ifp->frame_queue = av_fifo_alloc2(8, sizeof(AVFrame*), AV_FIFO_FLAG_AUTO_GROW);
     if (!ifp->frame_queue)
         report_and_exit(AVERROR(ENOMEM));
@@ -260,6 +275,9 @@  void fg_free(FilterGraph **pfg)
                 avsubtitle_free(&sub);
             av_fifo_freep2(&ist->sub2video.sub_queue);
         }
+
+        av_channel_layout_uninit(&ifp->fallback.ch_layout);
+
         av_buffer_unref(&ifilter->hw_frames_ctx);
         av_freep(&ifilter->name);
         av_freep(&fg->inputs[j]);
@@ -1361,6 +1379,29 @@  fail:
     return ret;
 }
 
+int ifilter_parameters_from_dec(InputFilter *ifilter, const AVCodecContext *dec)
+{
+    InputFilterPriv *ifp = ifp_from_ifilter(ifilter);
+
+    if (dec->codec_type == AVMEDIA_TYPE_VIDEO) {
+        ifp->fallback.format                 = dec->pix_fmt;
+        ifp->fallback.width                  = dec->width;
+        ifp->fallback.height                 = dec->height;
+        ifp->fallback.sample_aspect_ratio    = dec->sample_aspect_ratio;
+    } else {
+        int ret;
+
+        ifp->fallback.format                 = dec->sample_fmt;
+        ifp->fallback.sample_rate            = dec->sample_rate;
+
+        ret = av_channel_layout_copy(&ifp->fallback.ch_layout, &dec->ch_layout);
+        if (ret < 0)
+            return ret;
+    }
+
+    return 0;
+}
+
 static int ifilter_parameters_from_frame(InputFilter *ifilter, const AVFrame *frame)
 {
     AVFrameSideData *sd;
@@ -1469,12 +1510,18 @@  int ifilter_send_eof(InputFilter *ifilter, int64_t pts, AVRational tb)
         if (ret < 0)
             return ret;
     } else {
-        // the filtergraph was never configured
-        if (ifilter->format < 0) {
-            ret = ifilter_parameters_from_codecpar(ifilter, ifilter->ist->par);
-            if (ret < 0)
-                return ret;
-        }
+        // the filtergraph was never configured, use the fallback parameters
+        ifilter->format                 = ifp->fallback.format;
+        ifilter->sample_rate            = ifp->fallback.sample_rate;
+        ifilter->width                  = ifp->fallback.width;
+        ifilter->height                 = ifp->fallback.height;
+        ifilter->sample_aspect_ratio    = ifp->fallback.sample_aspect_ratio;
+
+        ret = av_channel_layout_copy(&ifilter->ch_layout,
+                                     &ifp->fallback.ch_layout);
+        if (ret < 0)
+            return ret;
+
         if (ifilter->format < 0 && (ifilter->type == AVMEDIA_TYPE_AUDIO || ifilter->type == AVMEDIA_TYPE_VIDEO)) {
             av_log(NULL, AV_LOG_ERROR, "Cannot determine format of input stream %d:%d after EOF\n", ifilter->ist->file_index, ifilter->ist->st->index);
             return AVERROR_INVALIDDATA;