ffmpeg: move field order decision making to encoder initialization

We now have the possibility of getting AVFrames here, and we should
not touch the muxer's codecpar after writing the header.

Results of FATE tests change as the MXF and Matroska muxers actually
write down the field/frame coding type of a stream in their
respective headers. Before this change, these values in codecpar
would only be set after the muxer was initialized. Now, the
information is also available for encoder and muxer initialization.

fftools/ffmpeg.c

@@ -1123,7 +1123,6 @@ static void do_video_out(OutputFile *of,
     int ret, format_video_sync;
     AVPacket pkt;
     AVCodecContext *enc = ost->enc_ctx;
-    AVCodecParameters *mux_par = ost->st->codecpar;
     AVRational frame_rate;
     int nb_frames, nb0_frames, i;
     double delta, delta0;
@@ -1285,18 +1284,6 @@ static void do_video_out(OutputFile *of,
         if (!check_recording_time(ost))
             return;
 
-        if (enc->flags & (AV_CODEC_FLAG_INTERLACED_DCT | AV_CODEC_FLAG_INTERLACED_ME) &&
-            ost->top_field_first >= 0)
-            in_picture->top_field_first = !!ost->top_field_first;
-
-        if (in_picture->interlaced_frame) {
-            if (enc->codec->id == AV_CODEC_ID_MJPEG)
-                mux_par->field_order = in_picture->top_field_first ? AV_FIELD_TT:AV_FIELD_BB;
-            else
-                mux_par->field_order = in_picture->top_field_first ? AV_FIELD_TB:AV_FIELD_BT;
-        } else
-            mux_par->field_order = AV_FIELD_PROGRESSIVE;
-
         in_picture->quality = enc->global_quality;
         in_picture->pict_type = 0;
 
@@ -3433,6 +3420,20 @@ static int init_output_stream_encode(OutputStream *ost, AVFrame *frame)
             enc_ctx->field_order = AV_FIELD_TT;
         }
 
+        if (frame) {
+            if (enc_ctx->flags & (AV_CODEC_FLAG_INTERLACED_DCT | AV_CODEC_FLAG_INTERLACED_ME) &&
+                ost->top_field_first >= 0)
+                frame->top_field_first = !!ost->top_field_first;
+
+            if (frame->interlaced_frame) {
+                if (enc_ctx->codec->id == AV_CODEC_ID_MJPEG)
+                    enc_ctx->field_order = frame->top_field_first ? AV_FIELD_TT:AV_FIELD_BB;
+                else
+                    enc_ctx->field_order = frame->top_field_first ? AV_FIELD_TB:AV_FIELD_BT;
+            } else
+                enc_ctx->field_order = AV_FIELD_PROGRESSIVE;
+        }
+
         if (ost->forced_keyframes) {
             if (!strncmp(ost->forced_keyframes, "expr:", 5)) {
                 ret = av_expr_parse(&ost->forced_keyframes_pexpr, ost->forced_keyframes+5,

tests/ref/fate/concat-demuxer-extended-lavf-mxf_d10

@@ -1 +1 @@
-d66177ea3922692bc91cd0f8aa907650 *tests/data/fate/concat-demuxer-extended-lavf-mxf_d10.ffprobe
+84496cfe2d668db395280ea67e5c6fbe *tests/data/fate/concat-demuxer-extended-lavf-mxf_d10.ffprobe

tests/ref/fate/concat-demuxer-simple1-lavf-mxf_d10

@@ -78,5 +78,5 @@ video|0|34|1.360000|34|1.360000|1|0.040000|N/A|N/A|150000|1924096|K_|1
 Strings Metadata
 audio|1|65280|1.360000|65280|1.360000|1920|0.040000|N/A|N/A|7680|2074624|K_|1
 Strings Metadata
-0|mpeg2video|0|video|1/25|[0][0][0][0]|0x0000|720|608|0|0|0|0|1:1|45:38|yuv422p|5|tv|unknown|unknown|unknown|topleft|tt|N/A|1|N/A|25/1|25/1|1/25|0|0.000000|N/A|N/A|30000000|N/A|N/A|N/A|N/A|35|0|0|0|0|0|0|0|0|0|0|0|0|0x060A2B340101010501010D001300000000000000000000000000000000000001
+0|mpeg2video|0|video|1/25|[0][0][0][0]|0x0000|720|608|0|0|0|0|1:1|45:38|yuv422p|5|tv|unknown|unknown|unknown|topleft|tb|N/A|1|N/A|25/1|25/1|1/25|0|0.000000|N/A|N/A|30000000|N/A|N/A|N/A|N/A|35|0|0|0|0|0|0|0|0|0|0|0|0|0x060A2B340101010501010D001300000000000000000000000000000000000001
 1|pcm_s16le|unknown|audio|1/48000|[0][0][0][0]|0x0000|s16|48000|2|unknown|16|N/A|0/0|0/0|1/48000|0|0.000000|N/A|N/A|1536000|N/A|N/A|N/A|N/A|35|0|0|0|0|0|0|0|0|0|0|0|0|0x060A2B340101010501010D001300000000000000000000000000000000000001

tests/ref/fate/rgb24-mkv

@@ -1,5 +1,5 @@
-fdc02d700dbe99315a9f0d928a9b935e *tests/data/fate/rgb24-mkv.matroska
-58213 tests/data/fate/rgb24-mkv.matroska
+fde8903c4df0ba8235dafcfd8a2f368c *tests/data/fate/rgb24-mkv.matroska
+58216 tests/data/fate/rgb24-mkv.matroska
 #tb 0: 1/10
 #media_type 0: video
 #codec_id 0: rawvideo

tests/ref/lavf/mxf_d10

@@ -1,3 +1,3 @@
-36fc2a640368f6d33987d2b2d39df966 *tests/data/lavf/lavf.mxf_d10
+da0ebbebb50a530b14c0f06017f464b3 *tests/data/lavf/lavf.mxf_d10
 5332013 tests/data/lavf/lavf.mxf_d10
 tests/data/lavf/lavf.mxf_d10 CRC=0x6c74d488