[FFmpeg-user] Average N frames of RTSP video for better snapshot quality?

[Steven Kan]

> On Mar 8, 2022, at 11:02 AM, Steven Kan <steven at kan.org> wrote:
> 
> 
>> On Mar 8, 2022, at 10:32 AM, Michael Koch <astroelectronic at t-online.de> wrote:
>> 
>> Am 08.03.2022 um 19:09 schrieb Steven Kan:
>>> After 7.5 years of waiting, my banana plant is finally flowering! I want to do a time-lapse capture of the flowering and fruiting process. Due to its location, the easiest way for me to get a camera out there is to use a little WyzeCam v3 with the RTSP firmware and the Wyze lamp socket. Unfortunately the WyzeCam doesn’t (yet) have a externally accessible JPG snapshot feature, so I have a cron job set up to:
>>> 
>>> ./ffmpeg -rtsp_transport tcp -i rtsp://anonymous:password@$IPAddress/live -frames:v 1 $outfile
>>> 
>>> every hour. The results are OK, but not fantastic:
>>> 
>>> https://www.kan.org/pictures/BananaTimeLapseFirstImage.jpg <https://www.kan.org/pictures/BananaTimeLapseFirstImage.jpg>
>>> 
>>> Is there a way to tell ffmpeg to collect N frames of video and output one single averaged image to improve the SNR? Even if there’s some wind, the flower stalk shouldn’t be moving much.
>>> 
>>> I tried:
>>> 
>>> ./ffmpeg -rtsp_transport tcp -i rtsp://anonymous:password@192.168.1.39/live -frames:v 10 ~/BananaLapse/MultiFrame%03d.jpg
>>> 
>>> and that results in N JPGs. I suppose I could have a second ffmpeg command that averages those 10 JPGs, but can this all be done in one pass? Thanks!
>> 
>> You can use the "tmix" filter before you extract the images from the video.
>> 
>> Michael
> 
> Thanks! Can I get a little help on the syntax? Right now it’s still expecting to output multiple images:
> 
> ./ffmpeg -rtsp_transport tcp -i rtsp://anonymous:password@192.168.1.39/live -frames:v 10 -vf tmix=frames=10:weights="1" ~/BananaLapse/MultiFrame.jpg

Ah, I think I figured it out. This works:

./ffmpeg -rtsp_transport tcp -i rtsp://anonymous:password@192.168.1.39/live -vf tmix=frames=10:weights="1" -frames:v 1 ~/BananaLapse/MultiFrame.jpg

I now have the -vf first, which averages 10 frames into 1, and then -frames:v expects only 1, correct? The output appears to be what I expect, with various values of N:

https://www.kan.org/pictures/MultiFrame1.jpg <https://www.kan.org/pictures/MultiFrame1.jpg>

https://www.kan.org/pictures/MultiFrame10.jpg <https://www.kan.org/pictures/MultiFrame10.jpg>

https://www.kan.org/pictures/MultiFrame128.jpg <https://www.kan.org/pictures/MultiFrame128.jpg>

And after all that I’m not sure it improves the image that much. I’ll check again at night, when the SNR will get worse.

Thanks for the help!