Stream MJPEG to file, but keep only last x minutes

Question

I'm looking to record a MJPEG stream on motion detected. But my motion detection notification is seconds later than the motion occurs.

To counter this, I want to record all the time, but only keep the last 2 minutes of footage.

Right now I'm downloading infinitely with cURL, but I'm stuck on how to have it trim the front of the file correctly to be 2 minutes.

Well, I'm recording it for hours, but I just need 2 minutes worth, on demand. But I don't want to waste the space. — St. John Johnson, Dec 26 '15 at 17:06

Edgar Rokjān · Accepted Answer · 2015-12-28T08:29:21.413

7

Look at segment muxer from FFmpeg.

With segment muxer it's possible to capture stream and write it to a number of separated files.

The option you may be interested in is segment_wrap.

From the documentation:

segment_wrap limit

Wrap around segment index once it reaches limit.

So you can use ffmpeg in this way:

ffmpeg -i URL -c copy -f segment -segment_time 120 -segment_wrap 2 out_file

to write cyclically two files.

The duration of each file is equal to the two minutes and in every moment of time you have at least last two minutes of video.

Of course I understand that this solution is terrible but it's the only way to solve your problem with ffmpeg that I can offer.

edited Dec 28 '15 at 08:29

answered Dec 26 '15 at 22:02

Edgar Rokjān

I don't think it's a terrible solution. You could add `-c copy` to stream copy instead of re-encoding. – llogan Dec 26 '15 at 22:21
@LordNeckbeard Thanks. I edited my answer and added `-c copy` option. – Edgar Rokjān Dec 26 '15 at 22:31
@LordNeckbeard But some containers don't work with some codecs. So in general copying codecs may lead to problems. – Edgar Rokjān Dec 26 '15 at 22:38
Just use an appropriate output container. If in doubt, .mkv. – llogan Dec 26 '15 at 22:44
This command gives me an error of "Invalid segment filename template". I found I have to include %d in the filename for this to work. – yeerk May 23 '18 at 06:29

1 Answers1