fftools/ffmpeg_filter: drop the OutputStream parameter to ofilter_bind_ost()

It is no longer used for anything besides a sanity-checking assert.
Rename the function to ofilter_bind_enc(), as it no longer has any
assumptions about the target being an output stream.

fftools/ffmpeg.h

@@ -772,7 +772,7 @@ const FrameData *frame_data_c(AVFrame *frame);
 FrameData       *packet_data  (AVPacket *pkt);
 const FrameData *packet_data_c(AVPacket *pkt);
 
-int ofilter_bind_ost(OutputFilter *ofilter, OutputStream *ost,
+int ofilter_bind_enc(OutputFilter *ofilter,
                      unsigned sched_idx_enc,
                      const OutputFilterOptions *opts);
 

fftools/ffmpeg_filter.c

@@ -783,8 +783,7 @@ static int set_channel_layout(OutputFilterPriv *f, const AVChannelLayout *layout
     return 0;
 }
 
-int ofilter_bind_ost(OutputFilter *ofilter, OutputStream *ost,
-                     unsigned sched_idx_enc,
+int ofilter_bind_enc(OutputFilter *ofilter, unsigned sched_idx_enc,
                      const OutputFilterOptions *opts)
 {
     OutputFilterPriv *ofp = ofp_from_ofilter(ofilter);
@@ -793,7 +792,8 @@ int ofilter_bind_ost(OutputFilter *ofilter, OutputStream *ost,
     int ret;
 
     av_assert0(!ofilter->bound);
-    av_assert0(ofilter->type == ost->type);
+    av_assert0(!opts->enc ||
+               ofilter->type == opts->enc->type);
 
     ofilter->bound = 1;
     av_freep(&ofilter->linklabel);
@@ -1222,7 +1222,7 @@ int init_simple_filtergraph(InputStream *ist, OutputStream *ost,
     if (ret < 0)
         return ret;
 
-    ret = ofilter_bind_ost(fg->outputs[0], ost, sched_idx_enc, opts);
+    ret = ofilter_bind_enc(fg->outputs[0], sched_idx_enc, opts);
     if (ret < 0)
         return ret;
 

fftools/ffmpeg_mux_init.c

@@ -1008,7 +1008,7 @@ ost_bind_filter(const Muxer *mux, MuxStream *ms, OutputFilter *ofilter,
 
     if (ofilter) {
         ost->filter = ofilter;
-        ret = ofilter_bind_ost(ofilter, ost, ms->sch_idx_enc, &opts);
+        ret = ofilter_bind_enc(ofilter, ms->sch_idx_enc, &opts);
     } else {
         ret = init_simple_filtergraph(ost->ist, ost, filters,
                                       mux->sch, ms->sch_idx_enc, &opts);