diff --git a/test/test_InfoExtractor.py b/test/test_InfoExtractor.py
index 40dd05e13..fee211899 100644
--- a/test/test_InfoExtractor.py
+++ b/test/test_InfoExtractor.py
@@ -1092,7 +1092,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'm4a',
                     'format_id': '318597',
-                    'format_note': 'DASH audio',
+                    'format_note': 'DASH audio, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'none',
@@ -1101,7 +1101,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': '318597',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 1',
                     'protocol': 'http_dash_segments',
                     'acodec': 'none',
                     'vcodec': 'avc1.42001f',
@@ -1112,7 +1112,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': '638590',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 1',
                     'protocol': 'http_dash_segments',
                     'acodec': 'none',
                     'vcodec': 'avc1.42001f',
@@ -1123,7 +1123,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': '1022565',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 1',
                     'protocol': 'http_dash_segments',
                     'acodec': 'none',
                     'vcodec': 'avc1.4d001f',
@@ -1134,7 +1134,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': '2046506',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 1',
                     'protocol': 'http_dash_segments',
                     'acodec': 'none',
                     'vcodec': 'avc1.4d001f',
@@ -1145,7 +1145,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': '3998017',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 1',
                     'protocol': 'http_dash_segments',
                     'acodec': 'none',
                     'vcodec': 'avc1.640029',
@@ -1156,7 +1156,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': '5997485',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 1',
                     'protocol': 'http_dash_segments',
                     'acodec': 'none',
                     'vcodec': 'avc1.640032',
@@ -1174,7 +1174,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_144p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1185,7 +1185,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_240p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1196,7 +1196,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_360p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1207,7 +1207,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_480p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1218,7 +1218,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_576p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1229,7 +1229,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_720p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1240,7 +1240,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'http://unknown/manifest.mpd',
                     'ext': 'mp4',
                     'format_id': 'h264_aac_1080p_m4s',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'protocol': 'http_dash_segments',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'avc3.42c01e',
@@ -1261,7 +1261,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'https://v.redd.it/hw1x7rcg7zl21/DASHPlaylist.mpd',
                     'ext': 'm4a',
                     'format_id': 'AUDIO-1',
-                    'format_note': 'DASH audio',
+                    'format_note': 'DASH audio, set 1',
                     'container': 'm4a_dash',
                     'acodec': 'mp4a.40.2',
                     'vcodec': 'none',
@@ -1273,7 +1273,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'https://v.redd.it/hw1x7rcg7zl21/DASHPlaylist.mpd',
                     'ext': 'mp4',
                     'format_id': 'VIDEO-2',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'container': 'mp4_dash',
                     'acodec': 'none',
                     'vcodec': 'avc1.4d401e',
@@ -1286,7 +1286,7 @@ def test_parse_mpd_formats(self):
                     'manifest_url': 'https://v.redd.it/hw1x7rcg7zl21/DASHPlaylist.mpd',
                     'ext': 'mp4',
                     'format_id': 'VIDEO-1',
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 0',
                     'container': 'mp4_dash',
                     'acodec': 'none',
                     'vcodec': 'avc1.4d401e',
@@ -1306,7 +1306,7 @@ def test_parse_mpd_formats(self):
                     'ext': 'm4a',
                     'tbr': 128.001,
                     'asr': 48000,
-                    'format_note': 'DASH audio',
+                    'format_note': 'DASH audio, set 1',
                     'container': 'm4a_dash',
                     'vcodec': 'none',
                     'acodec': 'mp4a.40.2',
@@ -1323,7 +1323,7 @@ def test_parse_mpd_formats(self):
                     'width': 336,
                     'height': 144,
                     'tbr': 100,
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 3',
                     'container': 'mp4_dash',
                     'vcodec': 'avc1.4D401F',
                     'acodec': 'none',
@@ -1340,7 +1340,7 @@ def test_parse_mpd_formats(self):
                     'width': 562,
                     'height': 240,
                     'tbr': 326,
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 3',
                     'container': 'mp4_dash',
                     'vcodec': 'avc1.4D401F',
                     'acodec': 'none',
@@ -1357,7 +1357,7 @@ def test_parse_mpd_formats(self):
                     'width': 844,
                     'height': 360,
                     'tbr': 698,
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 3',
                     'container': 'mp4_dash',
                     'vcodec': 'avc1.4D401F',
                     'acodec': 'none',
@@ -1374,7 +1374,7 @@ def test_parse_mpd_formats(self):
                     'width': 1126,
                     'height': 480,
                     'tbr': 1493,
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 3',
                     'container': 'mp4_dash',
                     'vcodec': 'avc1.4D401F',
                     'acodec': 'none',
@@ -1391,7 +1391,7 @@ def test_parse_mpd_formats(self):
                     'width': 1688,
                     'height': 720,
                     'tbr': 4482,
-                    'format_note': 'DASH video',
+                    'format_note': 'DASH video, set 3',
                     'container': 'mp4_dash',
                     'vcodec': 'avc1.4D401F',
                     'acodec': 'none',
diff --git a/yt_dlp/extractor/common.py b/yt_dlp/extractor/common.py
index 4a4b5416d..6a9be481e 100644
--- a/yt_dlp/extractor/common.py
+++ b/yt_dlp/extractor/common.py
@@ -2952,8 +2952,9 @@ def extract_Initialization(source):
                 'start_number': 1,
                 'timescale': 1,
             })
-            for adaptation_set in period.findall(_add_ns('AdaptationSet')):
+            for adaptation_idx, adaptation_set in enumerate(period.findall(_add_ns('AdaptationSet'))):
                 adaption_set_ms_info = extract_multisegment_info(adaptation_set, period_ms_info)
+                adaptation_set_label = try_call(lambda: adaptation_set.find(_add_ns('Label')).text)
                 for representation in adaptation_set.findall(_add_ns('Representation')):
                     representation_attrib = adaptation_set.attrib.copy()
                     representation_attrib.update(representation.attrib)
@@ -3017,7 +3018,10 @@ def extract_Initialization(source):
                             'asr': int_or_none(representation_attrib.get('audioSamplingRate')),
                             'fps': int_or_none(representation_attrib.get('frameRate')),
                             'language': lang if lang not in ('mul', 'und', 'zxx', 'mis') else None,
-                            'format_note': f'DASH {content_type}',
+                            # AdaptationSet ID/index must be included to prevent improper merging as periods
+                            'format_note': join_nonempty(
+                                f'DASH {content_type}', adaptation_set_label,
+                                f'set {adaptation_set.get("id", adaptation_idx)}', delim=', '),
                             'filesize': filesize,
                             'container': mimetype2ext(mime_type) + '_dash',
                             **codecs,