libnvidia-encode1

How it all started…

“I just want to record my screen.”

“Oh, you can use ffmpeg to do that.”

(the next day)

“My recording is flickering. Is it supposed to do that?”

“Oh, hmm…”

Prerequisites

  • You have a Debian Linux computer with a supported NVidia GPU.
  • You have the proprietary NVidia drivers installed.

Hardware-accelerated screen recording with ffmpeg

tl;dr: Try installing libnvidia-encode1.

From a Google search, the canonical article on the ffmpeg wiki appears to be here: https://trac.ffmpeg.org/wiki/Capture/Desktop

It include the following example:

$ ffmpeg -video_size 1024x768 -framerate 25 -f x11grab -i :0.0+100,200 output.mp4

Let’s try a minimal case:

$ ffmpeg -f x11grab -i :0.0 output.mp4
...
s speed=0.59x

Hmm, just outputting a 640x480 video with software encoding is not consistently real-time on this computer, when using software encoding.

But I know this computer has a recent NVidia card and the proprietary driver, so maybe we can use hardware encoding?

$ ffmpeg -encoders
...
 V..... h264_nvenc           NVIDIA NVENC H.264 encoder (codec h264)
...

Okay, looks like this ffmpeg was built with h264_nvenc. Let’s use it:

A screenshot of the following shell snippet.

$ ffmpeg -f x11grab -i :0.0 -c:v h264_nvenc output.mp4
...
[h264_nvenc @ 0x55a55bb9c360] The minimum required Nvidia driver for nvenc is 378.13 or newer
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!

Huh? I’m pretty sure a more recent driver is installed. I have 390.87, and I’m pretty sure that’s newer than 378.13.

A screenshot of the NVidia X Server Settings app.

Let’s look at that error message again…

Cannot load libnvidia-encode.so.1
[h264_nvenc @ 0x55a55bb9c360] The minimum required Nvidia driver for nvenc is 378.13 or newer
Error initializing output stream 0:0 -- Error while opening encoder for output stream #0:0 - maybe incorrect parameters such as bit_rate, rate, width or height
Conversion failed!

Failed to load libnvidia-encode.so.1? What package provides that? Turns out it’s a separate package called libnvidia-encode1:

$ sudo apt-get install libnvidia-encode1

And now our screen recording works:

$ ffmpeg -video_size 2560x1600 -f x11grab -i :0.0 -c:v h264_nvenc output.mp4

Hardware-accelerated screen recording with OBS

Install OBS, and libnvidia-encode1:

$ sudo apt-get install libnvidia-encode1 obs-studio

Configuring OBS to use NVENC

Hardware (NVENC) should just show up in the list of Encoders after installing libnvidia-encode1. (You may need to restart Open Broadcaster Software.)

If you don’t get the first-run wizard, delete ${HOME}/.config/obs-studio/. (Obviously, make a backup before you go deleting your OBS configuration…)

  1. Select optimize just for recording. (Unless you plan to stream, in which case you might want the extra dialogs for setting up the service you want to stream to.) Click Next.
  2. Pick some video settings. Click Next.
  3. Verify Recording Encoder: Hardware (NVENC). If it says Software, or tries to run an encoding benchmark, double-check that you installed libnvidia-encode1 and obs-studio. Click Apply Settings.
  4. Under Sources, click +, then Screen Capture (XSHM).
  5. In Create/Select Source dialog, click OK. In the Properties for ‘Screen Capture (XSHM)’ dialog, click OK. Your screen should now show in the preview area.

Recording only part of the screen with OBS

  1. Right-click the preview of the source you configured. Select Transform > Edit Transform…
  2. Specify the Crop in the Scene Item Transform dialog. Click Close.
  3. Click the Settings button (or File > Settings).
  4. Under Video, modify Base Resolution and Output Resolution as needed. You can type a custom resolution into the drop-down, like 1280x800, for both. Click OK.

Making a recording with OBS.

  1. Verify your screen capture source is selected.
  2. Click Start Recording. (You can also set a hotkey for this in Settings.)
  3. Perform the actions you want to record.
  4. Click Stop Recording. (You can also set a hotkey for this.)
  5. Recorded file will be created in the directory you set under Settings > Output > Recording Path. (By default, this is your home directory.)
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