Unable to build against FFmpeg5.1

[umlaeute]

Similar to x42/harvid#11, xjadeo also fails to build with FFmpeg-5.1 (see the harvid issue for details).

here's a more radical approach, that just unconditionally calls avcodec_flush_buffers() for all ffmpeg-versions:

--- xjadeo.orig/src/xjadeo/xjadeo.c
+++ xjadeo/src/xjadeo/xjadeo.c
@@ -575,9 +575,7 @@
 			seek = av_seek_frame (pFormatCtx, videoStream, fidx[framenumber].seekpts, AVSEEK_FLAG_BACKWARD);
 		}
 
-		if (pCodecCtx->codec->flush) {
-			avcodec_flush_buffers (pCodecCtx);
-		}
+		avcodec_flush_buffers (pCodecCtx);
 
 		if (seek < 0) {
 			if (!want_quiet)
@@ -915,9 +913,7 @@
 			error |= 16;
 			break;
 		}
-		if (pCodecCtx->codec->flush) {
-			avcodec_flush_buffers (pCodecCtx);
-		}
+		avcodec_flush_buffers (pCodecCtx);
 
 		int err = 0;
 		int bailout = 100;
@@ -1053,9 +1049,7 @@
 			printf("NOBYTE 2\n");
 			break;
 		}
-		if (pCodecCtx->codec->flush) {
-			avcodec_flush_buffers (pCodecCtx);
-		}
+		avcodec_flush_buffers (pCodecCtx);
 
 		int64_t pts = AV_NOPTS_VALUE;
 		while (!got_pic) {
@@ -1118,9 +1112,7 @@
 		} else {
 			av_seek_frame (pFormatCtx, videoStream, fidx[i].seekpts, AVSEEK_FLAG_BACKWARD);
 		}
-		if (pCodecCtx->codec->flush) {
-			avcodec_flush_buffers (pCodecCtx);
-		}
+		avcodec_flush_buffers (pCodecCtx);
 		while (!got_pic) {
 
 			if (av_read_frame (pFormatCtx, &packet) < 0) {
@@ -1192,9 +1184,7 @@
 	}
 
 	av_seek_frame (pFormatCtx, videoStream, 0, AVSEEK_FLAG_BACKWARD);
-	if (pCodecCtx->codec->flush) {
-		avcodec_flush_buffers (pCodecCtx);
-	}
+	avcodec_flush_buffers (pCodecCtx);
 	if (!error) {
 		scan_complete = 1;
 	}