Multifilemux messages and presicion

[Krutskikh Ivan]

Hi everyone

I want to use multifilesink element of gstreamer to record portions of
video from mjpeg/h264/h265 ip cams for both persistent and on-demand
recording.

I use gstreamer message bus to get veryfy the duration of recorded files
and mux them afterward to cold storage with ffmpeg. Right now I have
troubles with precision of those messages.

Simple test pipeline:

gst-launch-1.0 -m rtspsrc location=rtsp://192.168.15.102/av0_0 latency=0 !
rtph264depay  ! mpegtsmux  ! multifilesink next-file=5
location=/tmp/test/%05d.ts max-file-duration=3000000000 aggregate-gops=true
post-messages=1

So I want to store a set of 3 second long .ts files in ram and concat them
later in one mp4 file to persistent storage.

On message bus I get:

Получено сообщение #256 от элемента «multifilesink0» (element):
GstMultiFileSink, filename=(string)/tmp/test/00000.ts, index=(int)0,
timestamp=(guint64)3116261661, stream-time=(guint64)3116261661,
running-time=(guint64)3116261661, duration=(guint64)18446744073709551615,
offset=(guint64)18446744073709551615,
offset-end=(guint64)18446744073709551615;

Получено сообщение #257 от элемента «multifilesink0» (element):
GstMultiFileSink, filename=(string)/tmp/test/00001.ts, index=(int)1,
timestamp=(guint64)6141265420, stream-time=(guint64)6141265420,
running-time=(guint64)6141265420, duration=(guint64)18446744073709551615,
offset=(guint64)18446744073709551615,
offset-end=(guint64)18446744073709551615;

First of all, timestamp, stream_time, running-time are the same number and
as I assumed they mean time of pipeline running in nanoseconds.  duration
is always the same no matter how I change max-file-duration. Ok, I thought
that duration of fragment can be calculated as  (timestamp_current_file -
timestamp_last_file).

ffmpeg thinks different. My app calculates fragment durations with both
multipart timestamp and ffprobe format duration. Here's what I get:

Connection to base OK!
oper
backup
backup
Cleanup thread starting

/tmp/VKO-2/00000.ts
FFprobe duration  3.098689
Timestamp duration 3.112220846

/tmp/VKO-2/00001.ts
FFprobe duration  3.048089
Timestamp duration 3.001455997

/tmp/VKO-2/00002.ts
FFprobe duration  3.022633
Timestamp duration 3.003895173

/tmp/VKO-2/00003.ts
FFprobe duration  3.042733
Timestamp duration 3.000683485

/tmp/VKO-2/00004.ts
FFprobe duration  3.018056
Timestamp duration 3.003237973

This doesn't look to different, but when I concat those small files in 2
minutes interval I get a duration mismatch of 1-4 seconds or more when GOP
size is bigger.

For h264/h265 I can go with ffprobe although It's kinda ugly. But with
mjpeg I cannot find a suitable streaming muxer witch would tell me the
exact duration of video. Both multipartmux and matroskamux fail to do so.

What can I do in this situation?

Thanks in advance!
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