fix(dash): deduplicate multi-period SegmentBase segments

Multi-period DASH manifests using SegmentBase with shared BaseURLs were downloading the entire file once per period. Deduplicate identical segments across periods so each file is only downloaded once. Also demote multi-period log message from info to debug.

unshackle/core/manifests/dash.py

@@ -6,7 +6,6 @@ import logging
 import math
 import re
 import shutil
-import struct
 import sys
 from copy import copy
 from functools import partial
@@ -571,49 +570,6 @@ class DASH:
 
         progress(downloaded="Downloaded")
 
-    @staticmethod
-    def _parse_sidx(data: bytes, index_range: str) -> list[str]:
-        """Parse a SIDX box to extract per-segment byte ranges."""
-        # Find the sidx box in the data
-        offset = 0
-        while offset < len(data) - 8:
-            box_size = struct.unpack(">I", data[offset : offset + 4])[0]
-            if box_size < 8 or data[offset + 4 : offset + 8] != b"sidx":
-                offset += max(box_size, 8)
-                continue
-
-            pos = offset + 8
-            version = data[pos]
-            pos += 4  # version + flags
-            pos += 4  # reference_ID
-            pos += 4  # timescale
-
-            if version == 0:
-                first_offset = struct.unpack(">I", data[pos + 4 : pos + 8])[0]
-                pos += 8
-            else:
-                first_offset = struct.unpack(">Q", data[pos + 8 : pos + 16])[0]
-                pos += 16
-
-            pos += 2  # reserved
-            reference_count = struct.unpack(">H", data[pos : pos + 2])[0]
-            pos += 2
-
-            idx_end = int(index_range.split("-")[1])
-            current_offset = idx_end + 1 + first_offset
-            segments = []
-
-            for _ in range(reference_count):
-                ref_size = struct.unpack(">I", data[pos : pos + 4])[0] & 0x7FFFFFFF
-                pos += 12  # ref_info + subseg_duration + SAP fields
-                seg_end = current_offset + ref_size - 1
-                segments.append(f"{current_offset}-{seg_end}")
-                current_offset = seg_end + 1
-
-            return segments
-
-        return []
-
     @staticmethod
     def _is_content_period(period: Element, filtered_period_ids: list[str]) -> bool:
         """Check if a period is a valid content period (not an ad, not filtered, not trick mode)."""
@@ -814,19 +770,7 @@ class DASH:
                 if total_size:
                     media_range = f"{len(init_data)}-{total_size}"
 
-            # Parse SIDX box from indexRange to get per-segment byte ranges
+            segments.append((rep_base_url, media_range))
-            index_range = segment_base.get("indexRange")
-            if index_range:
-                sidx_res = session.get(url=rep_base_url, headers={"Range": f"bytes={index_range}"})
-                sidx_res.raise_for_status()
-                sidx_segments = DASH._parse_sidx(sidx_res.content, index_range)
-                if sidx_segments:
-                    for seg_range in sidx_segments:
-                        segments.append((rep_base_url, seg_range))
-                else:
-                    segments.append((rep_base_url, media_range))
-            else:
-                segments.append((rep_base_url, media_range))
         elif rep_base_url:
             segments.append((rep_base_url, None))