Add version checks to previous modifications to ffmpeg_cap_impl.hpp

Add version checks around uses of AVCodecID and av_opt_set, since these aren't
defined for older versions of ffmpeg.

modules/highgui/src/cap_ffmpeg_impl.hpp

@@ -1115,11 +1115,13 @@ static AVStream *icv_add_video_stream_FFMPEG(AVFormatContext *oc,
 
     c->codec_type = AVMEDIA_TYPE_VIDEO;
 
+#if LIBAVCODEC_BUILD >= CALC_FFMPEG_VERSION(54,25,0)
     // Set per-codec defaults
     AVCodecID c_id = c->codec_id;
     avcodec_get_context_defaults3(c, codec);
     // avcodec_get_context_defaults3 erases codec_id for some reason
     c->codec_id = c_id;
+#endif
 
     /* put sample parameters */
     int64_t lbit_rate = (int64_t)bitrate;
@@ -1183,16 +1185,20 @@ static AVStream *icv_add_video_stream_FFMPEG(AVFormatContext *oc,
         /* avoid FFMPEG warning 'clipping 1 dct coefficients...' */
         c->mb_decision=2;
     }
+
+#if LIBAVUTIL_BUILD > CALC_FFMPEG_VERSION(51,11,0)
     /* Some settings for libx264 encoding, restore dummy values for gop_size
      and qmin since they will be set to reasonable defaults by the libx264
      preset system. Also, use a crf encode with the default quality rating, 
      this seems easier than finding an appropriate default bitrate. */
-    if (c->codec_id == AV_CODEC_ID_H264) {
+    if (c->codec_id == CODEC_ID_H264) {
       c->gop_size = -1;
       c->qmin = -1;
       c->bit_rate = 0;
       av_opt_set(c->priv_data,"crf","23", 0);
     }
+#endif
+
 #if LIBAVCODEC_VERSION_INT>0x000409
     // some formats want stream headers to be seperate
     if(oc->oformat->flags & AVFMT_GLOBALHEADER)