ffmpeg: move setting video sync method to new_video_stream()

do_video_out() is the wrong place for it, since the necessary
information is already known when creating the stream and its value
should never change.

fftools/ffmpeg.c

@@ -1144,7 +1144,6 @@ static void do_video_out(OutputFile *of,
                          AVFrame *next_picture)
 {
     int ret;
-    enum VideoSyncMethod format_video_sync;
     AVPacket *pkt = ost->pkt;
     AVCodecContext *enc = ost->enc_ctx;
     AVRational frame_rate;
@@ -1191,28 +1190,10 @@ static void do_video_out(OutputFile *of,
         nb0_frames = 0; // tracks the number of times the PREVIOUS frame should be duplicated, mostly for variable framerate (VFR)
         nb_frames = 1;
 
-        format_video_sync = video_sync_method;
-        if (format_video_sync == VSYNC_AUTO) {
-            if(!strcmp(of->ctx->oformat->name, "avi")) {
-                format_video_sync = VSYNC_VFR;
-            } else
-                format_video_sync = (of->ctx->oformat->flags & AVFMT_VARIABLE_FPS) ? ((of->ctx->oformat->flags & AVFMT_NOTIMESTAMPS) ? VSYNC_PASSTHROUGH : VSYNC_VFR) : VSYNC_CFR;
-            if (   ist
-                && format_video_sync == VSYNC_CFR
-                && input_files[ist->file_index]->ctx->nb_streams == 1
-                && input_files[ist->file_index]->input_ts_offset == 0) {
-                format_video_sync = VSYNC_VSCFR;
-            }
-            if (format_video_sync == VSYNC_CFR && copy_ts) {
-                format_video_sync = VSYNC_VSCFR;
-            }
-        }
-        ost->is_cfr = (format_video_sync == VSYNC_CFR || format_video_sync == VSYNC_VSCFR);
-
         if (delta0 < 0 &&
             delta > 0 &&
-            format_video_sync != VSYNC_PASSTHROUGH &&
-            format_video_sync != VSYNC_DROP) {
+            ost->vsync_method != VSYNC_PASSTHROUGH &&
+            ost->vsync_method != VSYNC_DROP) {
             if (delta0 < -0.6) {
                 av_log(NULL, AV_LOG_VERBOSE, "Past duration %f too large\n", -delta0);
             } else
@@ -1222,7 +1203,7 @@ static void do_video_out(OutputFile *of,
             delta0 = 0;
         }
 
-        switch (format_video_sync) {
+        switch (ost->vsync_method) {
         case VSYNC_VSCFR:
             if (ost->frame_number == 0 && delta0 >= 0.5) {
                 av_log(NULL, AV_LOG_DEBUG, "Not duplicating %d initial frames\n", (int)lrintf(delta0));

fftools/ffmpeg.h

@@ -485,6 +485,7 @@ typedef struct OutputStream {
     /* video only */
     AVRational frame_rate;
     AVRational max_frame_rate;
+    enum VideoSyncMethod vsync_method;
     int is_cfr;
     int force_fps;
     int top_field_first;

fftools/ffmpeg_opt.c

@@ -1895,6 +1895,30 @@ static OutputStream *new_video_stream(OptionsContext *o, AVFormatContext *oc, in
         ost->top_field_first = -1;
         MATCH_PER_STREAM_OPT(top_field_first, i, ost->top_field_first, oc, st);
 
+        ost->vsync_method = video_sync_method;
+        if (ost->vsync_method == VSYNC_AUTO) {
+            if (!strcmp(oc->oformat->name, "avi")) {
+                ost->vsync_method = VSYNC_VFR;
+            } else {
+                ost->vsync_method = (oc->oformat->flags & AVFMT_VARIABLE_FPS)       ?
+                                     ((oc->oformat->flags & AVFMT_NOTIMESTAMPS) ?
+                                      VSYNC_PASSTHROUGH : VSYNC_VFR)                :
+                                     VSYNC_CFR;
+            }
+
+            if (ost->source_index >= 0 && ost->vsync_method == VSYNC_CFR) {
+                const InputStream *ist = input_streams[ost->source_index];
+                const InputFile *ifile = input_files[ist->file_index];
+
+                if (ifile->nb_streams == 1 && ifile->input_ts_offset == 0)
+                    ost->vsync_method = VSYNC_VSCFR;
+            }
+
+            if (ost->vsync_method == VSYNC_CFR && copy_ts) {
+                ost->vsync_method = VSYNC_VSCFR;
+            }
+        }
+        ost->is_cfr = (ost->vsync_method == VSYNC_CFR || ost->vsync_method == VSYNC_VSCFR);
 
         ost->avfilter = get_ost_filters(o, oc, ost);
         if (!ost->avfilter)