[FFmpeg-user] Trying to understand ffmpeg cpu usage in this case of capturing rtsp streams

[Ferdi Scholten]

Thanks so much for the help. Not sure why but when I try to upgrade ffmpeg
> using the ppa as you suggested I get:
>
> ffmpeg is already the newest version (7:4.4.2-0ubuntu0.22.04.1+esm5).
>
> however if I check with "ffmpeg -version " I get :
>
> ffmpeg version 4.4.2-0ubuntu0.22.04.1+esm5 Copyright (c) 2000-2021 the
> FFmpeg developers
> built with gcc 11 (Ubuntu 11.4.0-1ubuntu1~22.04)
>
> There is no 7 showing up in the version number, though  maybe I already
> have the newest version installed?
>
>
> On Thu, Nov 7, 2024 at 6:37 PM Ferdi Scholten<ferdi at sttc-nlp.nl>  wrote:
>
>> I'm using Ubuntu 22.04 and ffmpeg version 4.4.2-0
>>> I'm capturing 3 rtsp streams as shown at the bottom .
>>> Stream A resolution is 1600x1200
>>> Stream B and Stream C resolution is 384x192 .
>>> Stream A and B are coming from one device (ip address) and Stream C is
>>> coming from a second device (ip address)
>>>
>>> When I start Stream A and capture it with the command below I get a cpu
>>> usage of around 90% using the top command. If I then start stream B
>>> simultaneously it shows about 25% cpu usage in another ffmpeg instance.
>>>
>>> Then with the other 2 streams running I start Stream C and it shows about
>>> 90% cpu usage.
>>>
>>> If I start Stream B on it's own it shows 90% cpu usage.
>>>
>>> In other words it doesn't seem to matter what the resolution of the video
>>> coming in is but rather which stream starts first that determines the cpu
>>> usage. Does it matter that Stream A an B are coming from the same ip
>>> address and that explains why the second stream uses less cpu? My
>>> expectation is that Stream B and C would have the same cpu usage since
>> they
>>> are the same resolution just coming from different devices.  Can anyone
>>> explain what I see as strange behaviour. Stream commands follow.
>>>
>>>
>>> Stream A: ffmpeg -f rtsp -irtsp://192.168.35.243:8086/?camera=world  -f
>>> v4l2 /dev/video2
>>>
>>> Stream B: ffmpeg -f rtsp -irtsp://192.168.35.243:8086/?camera=eyes  -vf
>>> format=yuv420p  -f v4l2 /dev/video3
>>>
>>> Stream C: ffmpeg -f rtsp -irtsp://192.168.35.247:8086/?camera=eyes  -vf
>>> format=yuv420p  -f v4l2 /dev/video5
>>>
>>> Thanks,
>>> Jim
>>> _______________________________________________
>>>
>> Does this also happen if you use a less antique version of ffmpeg?
>> Either a static build or build it from git master or use a ppa? were at
>> version 7.1 now.
>> Current versions are much better in using multiple threads and there
>> have been numerous changes to internal code to improve the resource usage.
>>
>> for ease of use this ppa delivers ffmpeg 7.1 for ubuntu 22.04
>> https://ubuntuhandbook.org/index.php/2024/04/ffmpeg-7-0-ppa-ubuntu/
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>>
> Then the ppa was not correctly added to your apt sources.