Fix off-by-one in MP4 CTTS processing

Nevcairiel · Nov 11, 2022 · fd3c1c0 · fd3c1c0
1 parent 9fcd220
commit fd3c1c0
Showing 1 changed file with 8 additions and 13 deletions.
diff --git a/demuxer/Demuxers/LAVFDemuxer.cpp b/demuxer/Demuxers/LAVFDemuxer.cpp
@@ -2084,22 +2084,17 @@ STDMETHODIMP CLAVFDemuxer::GetKeyFrames(const GUID *pFormat, REFERENCE_TIME *pKF
                     timestamp += (sc->sample_offsets[i] + sc->dts_shift);
                 else if (sc->ctts_count)
                 {
-                    if (ctts_sample_counter > i)
+                    // find the next CTTS entry, if needed
+                    while (ctts_sample_counter <= i && ctts_index < sc->ctts_count)
                     {
-                        timestamp += (sc->ctts_data[ctts_index].duration + sc->dts_shift);
+                        ctts_sample_counter += sc->ctts_data[ctts_index++].count;
                     }
+
+                    // apply the CTTS offset to the timestamp
+                    if (ctts_sample_counter > i)
+                        timestamp += (sc->ctts_data[ctts_index - 1].duration + sc->dts_shift);
                     else
-                    {
-                        for (; ctts_index < sc->ctts_count; ctts_index++)
-                        {
-                            ctts_sample_counter += sc->ctts_data[ctts_index].count;
-                            if (ctts_sample_counter > i)
-                            {
-                                timestamp += (sc->ctts_data[ctts_index].duration + sc->dts_shift);
-                                break;
-                            }
-                        }
-                    }
+                        timestamp += (sc->min_corrected_pts + sc->dts_shift);
                 }
                 else
                     timestamp += (sc->min_corrected_pts + sc->dts_shift);