avcodec/er: remove check for fields

This change on its own is almost certainly not correct; however, in
testing, many samples show notable improvement.

Signed-off-by: J. Dekker <jdek@itanimul.li>

libavcodec/error_resilience.c

@@ -805,8 +805,7 @@ void ff_er_frame_start(ERContext *s)
 static int er_supported(ERContext *s)
 {
     if(s->avctx->hwaccel && s->avctx->hwaccel->decode_slice           ||
-       !s->cur_pic.f                                                  ||
-       s->cur_pic.field_picture
+       !s->cur_pic.f
     )
         return 0;
     return 1;
@@ -908,6 +907,12 @@ void ff_er_frame_end(ERContext *s)
                           (s->avctx->skip_top + s->avctx->skip_bottom)) {
         return;
     }
+
+    if (!s->warned_fields && (s->cur_pic.field_picture || s->cur_pic.f->interlaced_frame)) {
+        av_log(s->avctx, AV_LOG_WARNING, "Error concealment is not fully implemented for field pictures.\n");
+        s->warned_fields = 1;
+    }
+
     linesize = s->cur_pic.f->linesize;
 
     if (   s->avctx->codec_id == AV_CODEC_ID_MPEG2VIDEO

libavcodec/error_resilience.h

@@ -87,6 +87,7 @@ typedef struct ERContext {
                       int (*mv)[2][4][2],
                       int mb_x, int mb_y, int mb_intra, int mb_skipped);
     void *opaque;
+    int warned_fields;
 } ERContext;
 
 void ff_er_frame_start(ERContext *s);