diff --git a/src/isobmff/isobmff-demuxer.ts b/src/isobmff/isobmff-demuxer.ts
index d73e97d..f6a4b36 100644
--- a/src/isobmff/isobmff-demuxer.ts
+++ b/src/isobmff/isobmff-demuxer.ts
@@ -392,7 +392,7 @@ export class IsobmffDemuxer extends Demuxer {
 			// If they're not defined, we can simply use the decode timestamps as presentation timestamps
 		}
 
-		return internalTrack.sampleTable;
+		return sampleTable;
 	}
 
 	async readFragment(): Promise<Fragment> {
@@ -2239,7 +2239,8 @@ const getSampleIndexForTimestamp = (sampleTable: SampleTable, timescaleUnits: nu
 		}
 
 		const entry = sampleTable.sampleTimingEntries[index]!;
-		return entry.startIndex + Math.floor((timescaleUnits - entry.startDecodeTimestamp) / entry.delta);
+		return entry.startIndex
+			+ Math.min(Math.floor((timescaleUnits - entry.startDecodeTimestamp) / entry.delta), entry.count - 1);
 	}
 };
 
diff --git a/todo.txt b/todo.txt
index 2ed9e18..84501e1 100644
--- a/todo.txt
+++ b/todo.txt
@@ -3,4 +3,5 @@
 - Add the new audio codecs to muxers
 - Mov muxer!!! Only mov can hold PCM audio, MP4 cannot
 - Metadata methods for computing average fps and bitrate
-- A stream source?? Or like a callback-driven source
\ No newline at end of file
+- A stream source?? Or like a callback-driven source
+- onRead callback for Source
\ No newline at end of file