CODEWITHSUNDEEP
videoffmpeg
555Russich
555Russich

Reputation: 404

corrupted video after concat parts of captured RTSP stream with FFMPEG

Target: capture rtsp stream with sound from intercom camera and save it as 1hour duration video

URL for rtsp stream is updаting every 2 minutes, but i need to get parts with 1hour duration. So i see only solution to concatenate 2 minutes videos. It's required time between capturing stream parts to get response from server and reconnect with another url

First i tried opencv. It's not working with sound

Then i started using ffmpeg:

Capturing stream:

ffmpeg -rtsp_transport tcp -i <rtsp_url> 2min_part.mp4

Concatenating:

ffmpeg -safe 0 -f concat -i parts_list.txt -c copy concatenated_1.mp4

in stdout getting Non-monotonous DTS in output stream:

[mp4 @ 0x560c12d80bc0] Non-monotonous DTS in output stream 0:0; previous: 57400952, current: 41462297; changing to 57400953. This may result in incorrect timestamps in the output file.
[mp4 @ 0x560c12d80bc0] Non-monotonous DTS in output stream 0:0; previous: 57400953, current: 41462809; changing to 57400954. This may result in incorrect timestamps in the output file.
[mp4 @ 0x560c12d80bc0] Non-monotonous DTS in output stream 0:0; previous: 57400954, current: 41463321; changing to 57400955. This may result in incorrect timestamps in the output file.
...

After opening video in media players i see that from one second video is stopped, but sound is going on. Interesting part that with every new opening this second (starting from video stops) changes

Then i tried this solution:

ffmpeg -safe 0 -f concat -segment_time_metadata 1 -i parts_list.txt -vf select=concatdec_select -af aselect=concatdec_select,aresample=async=1 concatenated_2.mp4

No Non-monotonous DTS wаrnings, but video is still corrupted like first. Also this solution requires a lot of CPU while first concatenating method is very fast.

Question: How to do concatenating and get not corrupted video? May be i need to configure capturing options to simply use concatenating with -c copy?

parts of videos and concatenated

using exiftool concatenated_1.mp4 i see that:

Duration                        : 1:17:44
Track Duration                  : 1:17:44
Media Duration                  : 0:53:59

Upvotes: 0

Views: 545

Answers (1)

seeker
seeker

Reputation: 864

In your particular case, fixing the timestamps (-avoid_negative_ts make_zero) and setting the same timebase (-video_track_timescale 90000) help to avoid Non-monotonous DTS in output errors in case of using the concat demuxer. This command does the job without re-encoding (-c copy):

for f in Подъезд*.mp4; do
  num=${f##*_}
  num=${num%.*}
  num=$(printf "%02d" $num)
  ffmpeg -hide_banner -y -i $f \
    -avoid_negative_ts make_zero \
    -video_track_timescale 90000 \
    -c copy \
    part_${num}.mp4
done

Then you can use concat demuxer (without any error):

ffmpeg -hide_banner -y \
  -f concat -safe 0 \
  -i <(for f in part*.mp4; do echo "file '$PWD/$f'"; done) \
  -c copy \
  output.mp4

Upvotes: 1

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