I have an ffmpeg instance reading an rtsp stream from a camera and recording
two HLS streams (lo and hi b/w).
The HLS streams include EXT-X-PROGRAM-DATE-TIME, which the HLS client uses to
jump to precise times in the recordings.
ffmpeg is restarted at midnight with a new destination directory, so one
directory per day. So the EXT-X-PROGRAM-DATE-TIME timestamps normally start at
...T00:00:00.000+0000
If ffmpeg has to restart during the day, ie for maintenance of camera, server,
network, etc. then I add the HLS_FLAGS "append_list" and "discont_start" so
that the file sequence numbers continue and do not restart (which would delete
previously recorded video).
When these restarts happen ffmpeg continues to append to the .m3u8 file and add
.ts files with incremented sequence numbers. However, it also appears to
overwrite the timestamps. with incorrect ones. If I restart at 9:00 then when
the .m3u8 file is updated the (previously correct, 00:00:00.000) timestamp for
the first video file of the day will be replaced by an (incorrect) 00:09:00.000
value. All the EXT-X-PROGRAM-DATE-TIME timestamps are overwritten to show that
the playlist started at 9:00. In reality it started at 0:00 and recording was
re-started at 9:00.
I suspect that this is some weird interaction of my HLS_FLAGS... unless
somebody has another suggestions?
init string:
ffmpeg -hide_banner -loglevel info -rtbufsize 20M -f rtsp -rtsp_transport tcp
-stimeout 1000000 -probesize 10M \
-i
rtsp://192.168.0.52:554?recv_buffer_size=2000000&timeout=15000000/cam/realmonitor?channel=1&subtype=0
-f hls \
-hls_playlist_type event -hls_flags
program_date_time+independent_segments+append_list+discont_start \
-hls_time 5 -an -c:v h264_nvmpi -b:v 2M
/mnt/vod/Gate/2025-02-07/0-.m3u8 \
-hls_playlist_type event -hls_flags
program_date_time+independent_segments+append_list+discont_start \
-hls_time 5 -an -c:v h264_nvmpi -b:v 750K
/mnt/vod/Gate/2025-02-07/lo/0-.m3u8
ffmpeg -version
ffmpeg version 1076d31 Copyright (c) 2000-2023 the FFmpeg developers
built with gcc 7 (Ubuntu/Linaro 7.5.0-3ubuntu1~18.04)
configuration: --enable-nvmpi
libavutil 56. 31.100 / 56. 31.100
libavcodec 58. 54.100 / 58. 54.100
libavformat 58. 29.100 / 58. 29.100
libavdevice 58. 8.100 / 58. 8.100
libavfilter 7. 57.100 / 7. 57.100
libswscale 5. 5.100 / 5. 5.100
libswresample 3. 5.100 / 3. 5.100
Any and all suggestions welcome, to investigate further and/or to fix!
Cheers
Sean
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