avpacket: Replace av_free_packet with av_packet_unref

`av_packet_unref` matches the AVFrame ref-counted API and can be used as
a drop in replacement.

Deprecate `av_free_packet`.

doc/APIchanges

@@ -13,6 +13,10 @@ libavutil:     2015-08-28
 
 API changes, most recent first:
 
+2015-xx-xx - xxxxxxx - lavc 57.7.0 - avcodec.h
+  Deprecate av_free_packet(). Use av_packet_unref() as replacement,
+  it resets the packet in a more consistent way.
+
 2015-xx-xx - xxxxxxx - lavc 57.5.0 - avcodec.h
   Add data and linesize array to AVSubtitleRect, to be used instead of
   the ones from the embedded AVPicture.

doc/examples/avcodec.c

@@ -206,7 +206,7 @@ static void audio_encode_example(const char *filename)
         }
         if (got_output) {
             fwrite(pkt.data, 1, pkt.size, f);
-            av_free_packet(&pkt);
+            av_packet_unref(&pkt);
         }
     }
     fclose(f);
@@ -403,7 +403,7 @@ static void video_encode_example(const char *filename)
         if (got_output) {
             printf("encoding frame %3d (size=%5d)\n", i, pkt.size);
             fwrite(pkt.data, 1, pkt.size, f);
-            av_free_packet(&pkt);
+            av_packet_unref(&pkt);
         }
     }
 
@@ -420,7 +420,7 @@ static void video_encode_example(const char *filename)
         if (got_output) {
             printf("encoding frame %3d (size=%5d)\n", i, pkt.size);
             fwrite(pkt.data, 1, pkt.size, f);
-            av_free_packet(&pkt);
+            av_packet_unref(&pkt);
         }
     }
 

doc/examples/transcode_aac.c

@@ -337,7 +337,7 @@ static int decode_audio_frame(AVFrame *frame,
                                        data_present, &input_packet)) < 0) {
         fprintf(stderr, "Could not decode frame (error '%s')\n",
                 get_error_text(error));
-        av_free_packet(&input_packet);
+        av_packet_unref(&input_packet);
         return error;
     }
 
@@ -347,7 +347,7 @@ static int decode_audio_frame(AVFrame *frame,
      */
     if (*finished && *data_present)
         *finished = 0;
-    av_free_packet(&input_packet);
+    av_packet_unref(&input_packet);
     return 0;
 }
 
@@ -585,7 +585,7 @@ static int encode_audio_frame(AVFrame *frame,
                                        frame, data_present)) < 0) {
         fprintf(stderr, "Could not encode frame (error '%s')\n",
                 get_error_text(error));
-        av_free_packet(&output_packet);
+        av_packet_unref(&output_packet);
         return error;
     }
 
@@ -594,11 +594,11 @@ static int encode_audio_frame(AVFrame *frame,
         if ((error = av_write_frame(output_format_context, &output_packet)) < 0) {
             fprintf(stderr, "Could not write frame (error '%s')\n",
                     get_error_text(error));
-            av_free_packet(&output_packet);
+            av_packet_unref(&output_packet);
             return error;
         }
 
-        av_free_packet(&output_packet);
+        av_packet_unref(&output_packet);
     }
 
     return 0;