Mark 3D from REQ-VIDEO-LAYOUT, DV profile 20 codecs or an lhvC box; mux with MP4Box, decrypt with mp4decrypt, skip FFmpeg repack, sample cut and hybrid; add {3d} and env MP4Box.
Fix DASH SegmentTimeline negative @r and Pattern, TTML sidecar sets with no contentType, HLS CHANNELS identifiers and Dolby channel masks; test against 408 public DASH/HLS/ISM manifests.
Route titles with a dtsx/dtsy sample entry to MP4 via MP4Box, since Matroska has no CodecID for DTS-UHD. Add per-rendition HLS audio codec selection, fix merge_segments progress and its cleanup path.