examples/decoding_encoding: fix encoding when all frames got buffered.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

doc/examples/decoding_encoding.c

@@ -215,6 +215,7 @@ static void video_encode_example(const char *filename, int codec_id)
     FILE *f;
     AVFrame *picture;
     uint8_t *outbuf;
+    int had_output=0;
 
     printf("Video encoding\n");
 
@@ -284,15 +285,17 @@ static void video_encode_example(const char *filename, int codec_id)
 
         /* encode the image */
         out_size = avcodec_encode_video(c, outbuf, outbuf_size, picture);
+        had_output |= out_size;
         printf("encoding frame %3d (size=%5d)\n", i, out_size);
         fwrite(outbuf, 1, out_size, f);
     }
 
     /* get the delayed frames */
-    for(; out_size; i++) {
+    for(; out_size || !had_output; i++) {
         fflush(stdout);
 
         out_size = avcodec_encode_video(c, outbuf, outbuf_size, NULL);
+        had_output |= out_size;
         printf("write frame %3d (size=%5d)\n", i, out_size);
         fwrite(outbuf, 1, out_size, f);
     }