Unable to generate mpd required consisting multiple or pointing towards multiple mp4 timelines

[Pranay-Mayal]

I tried generating mpd file with the help of MP4Box and ffmpeg where i am passing paths to multiple mp4 files of 3 mins length each in case of MP4Box its taking time and duration for first mp4 file only if i am giving 10 mp4 it should be around 30 minutes but only showing duration of 3 minutes
MP4Box -dash 10000 -frag 5000
-rap -profile dashavc264:onDemand
-segment-name "segment_$Number$"
-url-template
recordings-3mins/REC_2025-02-25_18:36:13+0530.mp4
recordings-3mins/REC_2025-02-25_18:39:15+0530.mp4
recordings-3mins/REC_2025-02-25_18:42:15+0530.mp4
recordings-3mins/REC_2025-02-25_18:45:13+0530.mp4
recordings-3mins/REC_2025-02-25_18:48:13+0530.mp4
recordings-3mins/REC_2025-02-25_18:51:13+0530.mp4
recordings-3mins/REC_2025-02-25_18:54:13+0530.mp4
recordings-3mins/REC_2025-02-25_18:57:13+0530.mp4
recordings-3mins/REC_2025-02-25_19:00:13+0530.mp4
recordings-3mins/REC_2025-02-25_19:03:13+0530.mp4
recordings-3mins/REC_2025-02-25_19:06:14+0530.mp4
-out "test_output.mpd"

this creates multiple segments of videos as well if possible let me know how to use existing ones only not create new ones and tried using profile live and full still the same

then i tried to create with ffmpeg with
ffmpeg -f concat -safe 0 -i my_list.txt -c copy -f dash -seg_duration 4 -use_template 1 -use_timeline 1 -init_seg_name "init.mp4" -media_seg_name "segment_%d.m4s" test_output.mpd

this command where i am getting full duration but the whole video is being buffered at once and seeked till the last
basically i am trying to generate an mpd which can take multiple mp4 segments and if there is a missing mp4 can replace it with empty mp4 or a black frame for the missing duration