lavc/videotoolbox: deprecate write-only output_callback

This field has never been used for anything, so stop setting it and
deprecate it.

libavcodec/version_major.h

@@ -51,5 +51,6 @@
 #define FF_API_IDCT_NONE           (LIBAVCODEC_VERSION_MAJOR < 60)
 #define FF_API_SVTAV1_OPTS         (LIBAVCODEC_VERSION_MAJOR < 60)
 #define FF_API_AYUV_CODECID        (LIBAVCODEC_VERSION_MAJOR < 60)
+#define FF_API_VT_OUTPUT_CALLBACK  (LIBAVCODEC_VERSION_MAJOR < 60)
 
 #endif /* AVCODEC_VERSION_MAJOR_H */

libavcodec/videotoolbox.c

@@ -1377,8 +1377,6 @@ static AVVideotoolboxContext *av_videotoolbox_alloc_context_with_pix_fmt(enum AV
     AVVideotoolboxContext *ret = av_mallocz(sizeof(*ret));
 
     if (ret) {
-        ret->output_callback = videotoolbox_decoder_callback;
-
         OSType cv_pix_fmt_type = av_map_videotoolbox_format_from_pixfmt2(pix_fmt, full_range);
         if (cv_pix_fmt_type == 0) {
             cv_pix_fmt_type = kCVPixelFormatType_420YpCbCr8BiPlanarVideoRange;

libavcodec/videotoolbox.h

@@ -37,6 +37,8 @@
 
 #include "libavcodec/avcodec.h"
 
+#include "libavutil/attributes.h"
+
 /**
  * This struct holds all the information that needs to be passed
  * between the caller and libavcodec for initializing Videotoolbox decoding.
@@ -50,11 +52,14 @@ typedef struct AVVideotoolboxContext {
      */
     VTDecompressionSessionRef session;
 
+#if FF_API_VT_OUTPUT_CALLBACK
     /**
      * The output callback that must be passed to the session.
      * Set by av_videottoolbox_default_init()
      */
+    attribute_deprecated
     VTDecompressionOutputCallback output_callback;
+#endif
 
     /**
      * CVPixelBuffer Format Type that Videotoolbox will use for decoded frames.