Inconsistent fps while recording with ffmpeg

Autonomous Machines Jetson & Embedded Systems Jetson Xavier NX
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1

So I’m trying to record a video using this camera, my problem is that the fps fluctuate way too much.
To record a video I’m using ffmpeg, this version to be more precise, since there’s no support for nvenc with ffmpeg. The script to make the recording is a very simple one and can be reduced to this pseudocode.

while True:
----cam.grab_frame()
----ffmpeg_recorder.write_frame()

I can ensure that the camera grabs 67 frames per second and the frame captured it’s always the last one. FMPEG is called inside a thread and a queue is used for communication. The camera captures a 2592x1944 image and FFMPEG is set up so it can record a 1080p@60fps video. In reality at best I can capture 1080@50fps with hevc_nvmpi, this is fine. By the way I’m using ffmpeg-python to control the pipeline.

If I could capture 1080@50fps that would be enough for me but like I said at the start the fps fluctuate a lot under the same parameters. In what I call “good runs” the NVENC frequency is set at 499MHz and doesn’t change too much, in turn I record at 1080@50fps. My problem is with “bad runs” in wich the frequency gets stuck at 422 MHz so I can only record at 1080p@30-37 fps.

Some additional info, at first I thought this could be a problem related to the temperature my Jetson, so I increased the fan power from 50% to 100% this didn’t change much. The power mode as seen with jtop is NV POWER[2] 15W 6CORE. The temperature never goes above 50 C and it fluctuates between 43-47C.

Is there a way to solve this?

3

Hi,
Please refer to steps in
Jetson Nano FAQ
Q: I have a USB camera. How can I launch it on Jetson Nano?

See if you can launch it in gstreamer pipeline. If it can be launched, please try to replace nvoverlaysink with

... ! fpsdisplaysink text-overlay=0 video-sink=nvoverlaysink sync=0 -v

The fps information will be printed out with the plugin.

5

thanks for the quick response, but the cameras don’t appear in /dev/ in fact you need the Vimba API to make the connection. So I can’t directly launch it with GStreamer.

6

Hi,
Does it support capturing frames through v4l2? This is the default mode and most samples are demonstrated on the basis of it. If the camera runs in a different mode and requires additional driver, this would need other users to share experience.

8

Yeah, I will try to solve this, but also I’m going to run some tests with gstreamer, maybe it’s a better option.

9

got a way better experience using Gstreamer, reached 1080p60 easily.