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.

3 files changed, 19 insertions, 0 deletions

diff --git a/libavutil/frame.c b/libavutil/frame.c
index 9545477acc..5c9afb0d03 100644
--- a/libavutil/frame.c
+++ b/libavutil/frame.c
@@ -48,8 +48,12 @@ FF_DISABLE_DEPRECATION_WARNINGS
     frame->pkt_duration        = 0;
 FF_ENABLE_DEPRECATION_WARNINGS
 #endif
+#if FF_API_FRAME_PKT
+FF_DISABLE_DEPRECATION_WARNINGS
     frame->pkt_pos             = -1;
     frame->pkt_size            = -1;
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
     frame->time_base           = (AVRational){ 0, 1 };
     frame->key_frame           = 1;
     frame->sample_aspect_ratio = (AVRational){ 0, 1 };
@@ -279,8 +283,12 @@ static int frame_copy_props(AVFrame *dst, const AVFrame *src, int force_copy)
     dst->sample_rate            = src->sample_rate;
     dst->opaque                 = src->opaque;
     dst->pkt_dts                = src->pkt_dts;
+#if FF_API_FRAME_PKT
+FF_DISABLE_DEPRECATION_WARNINGS
     dst->pkt_pos                = src->pkt_pos;
     dst->pkt_size               = src->pkt_size;
+FF_ENABLE_DEPRECATION_WARNINGS
+#endif
 #if FF_API_PKT_DURATION
 FF_DISABLE_DEPRECATION_WARNINGS
     dst->pkt_duration           = src->pkt_duration;
diff --git a/libavutil/frame.h b/libavutil/frame.h
index 4ed27cf43f..5b58c14ac3 100644
--- a/libavutil/frame.h
+++ b/libavutil/frame.h
@@ -622,12 +622,17 @@ typedef struct AVFrame {
      */
     int64_t best_effort_timestamp;
 
+#if FF_API_FRAME_PKT
     /**
      * reordered pos from the last AVPacket that has been input into the decoder
      * - encoding: unused
      * - decoding: Read by user.
+     * @deprecated use AV_CODEC_FLAG_COPY_OPAQUE to pass through arbitrary user
+     *             data from packets to frames
      */
+    attribute_deprecated
     int64_t pkt_pos;
+#endif
 
 #if FF_API_PKT_DURATION
     /**
@@ -673,14 +678,19 @@ typedef struct AVFrame {
     int channels;
 #endif
 
+#if FF_API_FRAME_PKT
     /**
      * size of the corresponding packet containing the compressed
      * frame.
      * It is set to a negative value if unknown.
      * - encoding: unused
      * - decoding: set by libavcodec, read by user.
+     * @deprecated use AV_CODEC_FLAG_COPY_OPAQUE to pass through arbitrary user
+     *             data from packets to frames
      */
+    attribute_deprecated
     int pkt_size;
+#endif
 
     /**
      * For hwaccel-format frames, this should be a reference to the
diff --git a/libavutil/version.h b/libavutil/version.h
index a89a0d406f..93aa7a1050 100644
--- a/libavutil/version.h
+++ b/libavutil/version.h
@@ -114,6 +114,7 @@
 #define FF_API_REORDERED_OPAQUE         (LIBAVUTIL_VERSION_MAJOR < 59)
 #define FF_API_FRAME_PICTURE_NUMBER     (LIBAVUTIL_VERSION_MAJOR < 59)
 #define FF_API_HDR_VIVID_THREE_SPLINE   (LIBAVUTIL_VERSION_MAJOR < 59)
+#define FF_API_FRAME_PKT                (LIBAVUTIL_VERSION_MAJOR < 59)
 
 /**
  * @}