cbs_h264, h264_metadata: Deleting SEI messages never fails

Given the recent changes to ff_cbs_delete_unit, it is no longer sensible
to use a return value for ff_cbs_h264_delete_sei_message; instead, use
asserts to ensure that the required conditions are met and remove the
callers' checks for the return value. Also, document said conditions.

An assert that is essentially equivalent to the one used in
ff_cbs_delete_unit has been removed, too.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

libavcodec/cbs_h264.h

@@ -478,10 +478,13 @@ int ff_cbs_h264_add_sei_message(CodedBitstreamContext *ctx,
  *
  * Deletes from nal_unit, which must be an SEI NAL unit.  If this is the
  * last message in nal_unit, also deletes it from access_unit.
+ *
+ * Requires nal_unit to be a unit in access_unit and position to be >= 0
+ * and < the payload count of the SEI nal_unit.
  */
-int ff_cbs_h264_delete_sei_message(CodedBitstreamContext *ctx,
-                                   CodedBitstreamFragment *access_unit,
-                                   CodedBitstreamUnit *nal_unit,
-                                   int position);
+void ff_cbs_h264_delete_sei_message(CodedBitstreamContext *ctx,
+                                    CodedBitstreamFragment *access_unit,
+                                    CodedBitstreamUnit *nal_unit,
+                                    int position);
 
 #endif /* AVCODEC_CBS_H264_H */

libavcodec/cbs_h2645.c

@@ -1644,10 +1644,10 @@ int ff_cbs_h264_add_sei_message(CodedBitstreamContext *ctx,
     return 0;
 }
 
-int ff_cbs_h264_delete_sei_message(CodedBitstreamContext *ctx,
-                                   CodedBitstreamFragment *au,
-                                   CodedBitstreamUnit *nal,
-                                   int position)
+void ff_cbs_h264_delete_sei_message(CodedBitstreamContext *ctx,
+                                    CodedBitstreamFragment *au,
+                                    CodedBitstreamUnit *nal,
+                                    int position)
 {
     H264RawSEI *sei = nal->content;
 
@@ -1662,7 +1662,6 @@ int ff_cbs_h264_delete_sei_message(CodedBitstreamContext *ctx,
             if (&au->units[i] == nal)
                 break;
         }
-        av_assert0(i < au->nb_units && "NAL unit not in access unit.");
 
         ff_cbs_delete_unit(ctx, au, i);
     } else {
@@ -1673,6 +1672,4 @@ int ff_cbs_h264_delete_sei_message(CodedBitstreamContext *ctx,
                 sei->payload + position + 1,
                 (sei->payload_count - position) * sizeof(*sei->payload));
     }
-
-    return 0;
 }

libavcodec/h264_metadata_bsf.c

@@ -437,15 +437,9 @@ static int h264_metadata_filter(AVBSFContext *bsf, AVPacket *pkt)
 
                 for (j = sei->payload_count - 1; j >= 0; j--) {
                     if (sei->payload[j].payload_type ==
-                        H264_SEI_TYPE_FILLER_PAYLOAD) {
-                        err = ff_cbs_h264_delete_sei_message(ctx->cbc, au,
-                                                             &au->units[i], j);
-                        if (err < 0) {
-                            av_log(bsf, AV_LOG_ERROR, "Failed to delete "
-                                   "filler SEI message.\n");
-                            goto fail;
-                        }
-                    }
+                        H264_SEI_TYPE_FILLER_PAYLOAD)
+                        ff_cbs_h264_delete_sei_message(ctx->cbc, au,
+                                                       &au->units[i], j);
                 }
             }
         }
@@ -469,13 +463,8 @@ static int h264_metadata_filter(AVBSFContext *bsf, AVPacket *pkt)
 
                 if (ctx->display_orientation == REMOVE ||
                     ctx->display_orientation == INSERT) {
-                    err = ff_cbs_h264_delete_sei_message(ctx->cbc, au,
-                                                         &au->units[i], j);
-                    if (err < 0) {
-                        av_log(bsf, AV_LOG_ERROR, "Failed to delete "
-                               "display orientation SEI message.\n");
-                        goto fail;
-                    }
+                    ff_cbs_h264_delete_sei_message(ctx->cbc, au,
+                                                   &au->units[i], j);
                     continue;
                 }