lavu/frame: deprecate AVFrame.pkt_{pos,size}

These fields are supposed to store information about the packet the
frame was decoded from, specifically the byte offset it was stored at
and its size.

However,
- the fields are highly ad-hoc - there is no strong reason why
  specifically those (and not any other) packet properties should have a
  dedicated field in AVFrame; unlike e.g. the timestamps, there is no
  fundamental link between coded packet offset/size and decoded frames
- they only make sense for frames produced by decoding demuxed packets,
  and even then it is not always the case that the encoded data was
  stored in the file as a contiguous sequence of bytes (in order for pos
  to be well-defined)
- pkt_pos was added without much explanation, apparently to allow
  passthrough of this information through lavfi in order to handle byte
  seeking in ffplay. That is now implemented using arbitrary user data
  passthrough in AVFrame.opaque_ref.
- several filters use pkt_pos as a variable available to user-supplied
  expressions, but there seems to be no established motivation for using them.
- pkt_size was added for use in ffprobe, but that too is now handled
  without using this field. Additonally, the values of this field
  produced by libavcodec are flawed, as described in the previous
  ffprobe conversion commit.

In summary - these fields are ill-defined and insufficiently motivated,
so deprecate them.

1 files changed, 13 insertions, 3 deletions

diff --git a/libavfilter/af_volume.c b/libavfilter/af_volume.c
index f6e183df8d..926529947c 100644
--- a/libavfilter/af_volume.c
+++ b/libavfilter/af_volume.c
@@ -48,7 +48,9 @@ static const char *const var_names[] = {
     "nb_channels",         ///< number of channels
     "nb_consumed_samples", ///< number of samples consumed by the filter
     "nb_samples",          ///< number of samples in the current frame
+#if FF_API_FRAME_PKT
     "pos",                 ///< position in the file of the frame
+#endif
     "pts",                 ///< frame presentation timestamp
     "sample_rate",         ///< sample rate
     "startpts",            ///< PTS at start of stream
@@ -288,7 +290,9 @@ static int config_output(AVFilterLink *outlink)
     vol->var_values[VAR_N] =
     vol->var_values[VAR_NB_CONSUMED_SAMPLES] =
     vol->var_values[VAR_NB_SAMPLES] =
+#if FF_API_FRAME_PKT
     vol->var_values[VAR_POS] =
+#endif
     vol->var_values[VAR_PTS] =
     vol->var_values[VAR_STARTPTS] =
     vol->var_values[VAR_STARTT] =
@@ -330,7 +334,6 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
     AVFilterLink *outlink = inlink->dst->outputs[0];
     int nb_samples        = buf->nb_samples;
     AVFrame *out_buf;
-    int64_t pos;
     AVFrameSideData *sd = av_frame_get_side_data(buf, AV_FRAME_DATA_REPLAYGAIN);
     int ret;
 
@@ -380,8 +383,15 @@ static int filter_frame(AVFilterLink *inlink, AVFrame *buf)
     vol->var_values[VAR_T  ] = TS2T(buf->pts, inlink->time_base);
     vol->var_values[VAR_N  ] = inlink->frame_count_out;
 
-    pos = buf->pkt_pos;
-    vol->var_values[VAR_POS] = pos == -1 ? NAN : pos;
+#if FF_API_FRAME_PKT
+FF_DISABLE_DEPRECATION_WARNINGS
+    {
+        int64_t pos;
+        pos = buf->pkt_pos;
+        vol->var_values[VAR_POS] = pos == -1 ? NAN : pos;
+    }
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
     if (vol->eval_mode == EVAL_MODE_FRAME)
         set_volume(ctx);