Subject: [PATCH 2/2] avformat/mxf: stop parsing if index table is coherent
From: Marc-Antoine Arnaud <[email-masked]>
To: [email-masked]
Date: Sat, 13 Jul 2024 18:26:15 +0200

sponsored by nxtedition

Signed-off-by: Marc-Antoine Arnaud <[email-masked]>
---
 libavformat/mxfdec.c | 56 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)

diff --git a/libavformat/mxfdec.c b/libavformat/mxfdec.c
index df958819300..83f9e5fc9e0 100644
--- a/libavformat/mxfdec.c
+++ b/libavformat/mxfdec.c
@@ -2063,6 +2063,52 @@ static int mxf_compute_ptses_fake_index(MXFContext *mxf, MXFIndexTable *index_ta
     return 0;
 }
 
+static int mxf_validate_coherent_index_tables(MXFContext *mxf, int *is_coherent) {
+      int i, j, ret, nb_sorted_segments = 0;
+      MXFIndexTable *index_tables;
+      int nb_index_tables = 0;
+      int coherent_index_tables = 1;
+      MXFIndexTableSegment **sorted_segments = NULL;
+
+      ret = mxf_get_sorted_table_segments(mxf, &nb_sorted_segments, &sorted_segments);
+
+      index_tables = av_calloc(nb_index_tables, sizeof(MXFIndexTable));
+      if (!index_tables) {
+          av_log(mxf->fc, AV_LOG_ERROR, "failed to allocate index tables\n");
+          av_free(sorted_segments);
+          return AVERROR(ENOMEM);
+      }
+
+      /* distribute sorted segments to index tables */
+      for (i = j = 0; i < nb_sorted_segments; i++) {
+          if (i != 0 && sorted_segments[i-1]->index_sid != sorted_segments[i]->index_sid) {
+              /* next IndexSID */
+              j++;
+          }
+
+          index_tables[j].nb_segments++;
+      }
+
+      for (i = j = 0; j < nb_index_tables; i += index_tables[j++].nb_segments) {
+          if (sorted_segments[i]->index_start_position) {
+              av_log(mxf->fc, AV_LOG_WARNING, "IndexSID %i starts at EditUnit %"PRId64" - seeking may not work as expected\n",
+                     sorted_segments[i]->index_sid, sorted_segments[i]->index_start_position);
+              coherent_index_tables = 0;
+          }
+      }
+
+      av_free(sorted_segments);
+
+      if (ret == 0 && coherent_index_tables) {
+        *is_coherent = 1;
+      } else {
+        *is_coherent = 0;
+      }
+
+      return 0;
+}
+
+
 /**
  * Sorts and collects index table segments into index tables.
  * Also computes PTSes if possible.
@@ -3752,6 +3798,16 @@ static int mxf_read_header(AVFormatContext *s)
             if (!essence_offset)
                 essence_offset = klv.offset;
 
+            if (mxf->mxf_inspect_mode == 1) {
+                int ret_local, coherent_index_tables;
+                ret_local = mxf_validate_coherent_index_tables(mxf, &coherent_index_tables);
+
+                // Break only if index table is coherent
+                if (ret_local == 0 && coherent_index_tables == 1) {
+                  break;
+                }
+            }
+
             /* seek to footer, previous partition or stop */
             if (mxf_parse_handle_essence(mxf) <= 0)
                 break;
-- 
2.39.3 (Apple Git-146)