add a helper function to get sample entry type more easily

Author: podborski

IsoLib/libisomediafile/src/MP4Movies.c

@@ -791,6 +791,33 @@ MP4GetMovieIndTrack(MP4Movie theMovie, u32 trackIndex, MP4Track *outTrack)
   return err;
 }
 
+MP4_EXTERN(MP4Err)
+MP4GetMovieIndTrackSampleEntryType(MP4Movie theMovie, u32 idx, u32* SEType)
+{
+  MP4Err err;
+  MP4Track trak;
+  MP4TrackReader reader;
+  MP4Handle sampleEntryH;
+
+  MP4NewHandle(0, &sampleEntryH);
+
+  err = MP4GetMovieIndTrack(theMovie, idx, &trak);
+  if(err) goto bail;
+
+  err = MP4CreateTrackReader(trak, &reader);
+  if(err) goto bail;
+
+  err = MP4TrackReaderGetCurrentSampleDescription(reader, sampleEntryH);
+  if(err) goto bail;
+
+  err = ISOGetSampleDescriptionType(sampleEntryH, SEType);
+
+bail:
+  TEST_RETURN(err);
+  MP4DisposeHandle(sampleEntryH);
+  return err;
+}
+
 MP4_EXTERN(MP4Err)
 MP4GetMovieTrack(MP4Movie theMovie, u32 trackID, MP4Track *outTrack)
 {

IsoLib/libisomediafile/src/MP4Movies.h

@@ -745,6 +745,15 @@ extern "C"
    * @return MP4Err error code
    */
   MP4_EXTERN(MP4Err) MP4GetMovieIndTrack(MP4Movie theMovie, u32 trackIndex, MP4Track *outTrack);
+  /**
+   * @brief Get sample entry type of a track.
+   *
+   * @note This function only returns the first sample entry type.
+   * @param theMovie input movie object
+   * @param idx index of the track ranges between 1 and the number of tracks in theMovie.
+   * @param SEType [out] sample entry type (4CC)
+   */
+  MP4_EXTERN(MP4Err) MP4GetMovieIndTrackSampleEntryType(MP4Movie theMovie, u32 idx, u32* SEType);
 
   /*
   MP4_EXTERN ( MP4Err )

test/test_01_simple.cpp

@@ -22,6 +22,7 @@
 
 #include <catch.hpp>
 #include <ISOMovies.h>
+#include <MP4Atoms.h>
 #include "testdataPath.h"
 
 #include <string>
@@ -118,6 +119,30 @@ TEST_CASE("01_simple.mp4")
     CHECK(err == MP4NoErr);
     CHECK(uiTrackCnt == 4);
 
+    for(uint32_t i=1; i<=uiTrackCnt; i++)
+    {
+      uint32_t type = 0; 
+      err = MP4GetMovieIndTrackSampleEntryType(cMovieBox, i, &type);
+      CHECK(err == MP4NoErr);
+      switch (i)
+      {
+      case 1:
+        CHECK(type == MP4MPEGSampleEntryAtomType);
+        break;
+      case 2:
+        CHECK(type == MP4MPEGSampleEntryAtomType);
+        break;
+      case 3:
+        CHECK(type == MP4VisualSampleEntryAtomType);
+        break;
+      case 4:
+        CHECK(type == MP4AudioSampleEntryAtomType);
+        break;
+      default:
+        break;
+      }
+    }
+
     // ISOGetTrackEnabled
     u32 outEnabled;
     ISOGetMovieTrack(cMovieBox, 101, &audioTrack);