fix for build errors with FFMpeg version 6 (#489)

* fix for build errors with FFMpeg version 6

* set initialize for reconfigure

[ROCm/rocdecode commit: f02751900d]

projects/rocdecode/utils/ffmpegvideodecode/ffmpeg_video_dec.h

@@ -214,6 +214,7 @@ class FFMpegVideoDecoder: public RocVideoDecoder {
         typedef enum { STATUS_SUCCESS = 0, STATUS_FAILURE = -1 } StatusType;
 
         bool no_multithreading_ = false;
+        bool b_decoder_initialized = false;
         uint32_t av_frame_cnt_ = 0;
         uint32_t av_pkt_cnt_ = 0;
         RocdecSourceDataPacket last_packet_;
@@ -230,7 +231,11 @@ class FFMpegVideoDecoder: public RocVideoDecoder {
         // Variables for FFMpeg decoding
         AVCodecContext * dec_context_ = nullptr;
         AVPixelFormat decoder_pixel_format_;
+#if USE_AVCODEC_GREATER_THAN_58_134
+        const AVCodec *_decoder = nullptr;
+#else
         AVCodec *decoder_ = nullptr;
+#endif
         AVFormatContext * formatContext = nullptr;
         AVInputFormat * inputFormat = nullptr;
         AVStream *video = nullptr;