fftools/ffmpeg_filter: pass sub2video canvas size through InputFilterOptions

Rather than read them directly from InputStream.

This is a step towards avoiding the assumption that filtergraph inputs
are always fed by demuxers.

fftools/ffmpeg.h

@@ -255,6 +255,9 @@ typedef struct InputFilterOptions {
     int64_t             trim_end_us;
 
     uint8_t            *name;
+
+    int                 sub2video_width;
+    int                 sub2video_height;
 } InputFilterOptions;
 
 typedef struct InputFilter {
@@ -366,10 +369,6 @@ typedef struct InputStream {
 
     int                   fix_sub_duration;
 
-    struct sub2video {
-        int w, h;
-    } sub2video;
-
     /* decoded data from this stream goes into all those filters
      * currently video and audio only */
     InputFilter         **filters;

fftools/ffmpeg_demux.c

@@ -992,6 +992,26 @@ int ist_filter_add(InputStream *ist, InputFilter *ifilter, int is_simple,
         return ret;
 
     if (ist->par->codec_type == AVMEDIA_TYPE_SUBTITLE) {
+        /* Compute the size of the canvas for the subtitles stream.
+           If the subtitles codecpar has set a size, use it. Otherwise use the
+           maximum dimensions of the video streams in the same file. */
+        opts->sub2video_width  = ist->par->width;
+        opts->sub2video_height = ist->par->height;
+        if (!(opts->sub2video_width && opts->sub2video_height)) {
+            for (int j = 0; j < d->f.nb_streams; j++) {
+                AVCodecParameters *par1 = d->f.streams[j]->par;
+                if (par1->codec_type == AVMEDIA_TYPE_VIDEO) {
+                    opts->sub2video_width  = FFMAX(opts->sub2video_width,  par1->width);
+                    opts->sub2video_height = FFMAX(opts->sub2video_height, par1->height);
+                }
+            }
+        }
+
+        if (!(opts->sub2video_width && opts->sub2video_height)) {
+            opts->sub2video_width  = FFMAX(opts->sub2video_width,  720);
+            opts->sub2video_height = FFMAX(opts->sub2video_height, 576);
+        }
+
         if (!d->pkt_heartbeat) {
             d->pkt_heartbeat = av_packet_alloc();
             if (!d->pkt_heartbeat)
@@ -1357,27 +1377,6 @@ static int ist_add(const OptionsContext *o, Demuxer *d, AVStream *st)
                 return ret;
             }
         }
-
-        /* Compute the size of the canvas for the subtitles stream.
-           If the subtitles codecpar has set a size, use it. Otherwise use the
-           maximum dimensions of the video streams in the same file. */
-        ist->sub2video.w = par->width;
-        ist->sub2video.h = par->height;
-        if (!(ist->sub2video.w && ist->sub2video.h)) {
-            for (int j = 0; j < ic->nb_streams; j++) {
-                AVCodecParameters *par1 = ic->streams[j]->codecpar;
-                if (par1->codec_type == AVMEDIA_TYPE_VIDEO) {
-                    ist->sub2video.w = FFMAX(ist->sub2video.w, par1->width);
-                    ist->sub2video.h = FFMAX(ist->sub2video.h, par1->height);
-                }
-            }
-        }
-
-        if (!(ist->sub2video.w && ist->sub2video.h)) {
-            ist->sub2video.w = FFMAX(ist->sub2video.w, 720);
-            ist->sub2video.h = FFMAX(ist->sub2video.h, 576);
-        }
-
         break;
     }
     case AVMEDIA_TYPE_ATTACHMENT:

fftools/ffmpeg_filter.c

@@ -689,6 +689,16 @@ static int ifilter_bind_ist(InputFilter *ifilter, InputStream *ist)
         ifp->sub2video.frame = av_frame_alloc();
         if (!ifp->sub2video.frame)
             return AVERROR(ENOMEM);
+
+        ifp->width  = ifp->opts.sub2video_width;
+        ifp->height = ifp->opts.sub2video_height;
+
+        /* rectangles are AV_PIX_FMT_PAL8, but we have no guarantee that the
+           palettes for all rectangles are identical or compatible */
+        ifp->format = AV_PIX_FMT_RGB32;
+
+        av_log(fgp, AV_LOG_VERBOSE, "sub2video: using %dx%d canvas\n",
+               ifp->width, ifp->height);
     }
 
     return 0;
@@ -1829,17 +1839,6 @@ int ifilter_parameters_from_dec(InputFilter *ifilter, const AVCodecContext *dec)
         ret = av_channel_layout_copy(&ifp->fallback.ch_layout, &dec->ch_layout);
         if (ret < 0)
             return ret;
-    } else {
-        // for subtitles (i.e. sub2video) we set the actual parameters,
-        // rather than just fallback
-        ifp->width  = ifp->ist->sub2video.w;
-        ifp->height = ifp->ist->sub2video.h;
-
-        /* rectangles are AV_PIX_FMT_PAL8, but we have no guarantee that the
-           palettes for all rectangles are identical or compatible */
-        ifp->format = AV_PIX_FMT_RGB32;
-
-        av_log(NULL, AV_LOG_VERBOSE, "sub2video: using %dx%d canvas\n", ifp->width, ifp->height);
     }
 
     return 0;