FFMPEG Execute Command Node Not Working

[Nick_B]

Hello n8n Community,

I am encountering a persistent and frustrating bug with the Execute Command node on a self-hosted n8n instance (Elestio deployment on Alpine Linux/Docker). The issue is that dynamic expressions for binary file paths are resolving to empty strings, despite the data being correctly input and the syntax being verified.

I have exhausted all known troubleshooting steps. I am hoping a community expert who has seen this specific environment failure can offer a solution.

The Goal: Burn styled subtitles onto a video using FFmpeg in the Execute Command node.

The Setup:

• Host Environment: Elestio (Alpine Linux/Docker).

• FFmpeg Status: Confirmed installed and executable (ffmpeg -version runs successfully).

The Problem (Expression Fails):

**I tried both of these but they didn’t work, and expressions are always red/undefined:
**
INPUT_VIDEO=“{{$binary.video_file.filePath}}”; SUBTITLES_SRT=“{{$binary[‘subtitles.srt’].filePath}}”; ffmpeg -i “$INPUT_VIDEO” -vf “subtitles=‘$SUBTITLES_SRT’:force_style=‘fontname=Arial,fontsize=28,outline=1,borderstyle=3,backcolor=&H80000000,primary_color=&H00FFFF’” -c:v libx264 -crf 23 -y /tmp/output_final.mp4

INPUT_VIDEO=“{{$binary.video_file.filePath}}”; SUBTITLES_SRT=“{{$binary.subtitles.srt.filePath}}”; ffmpeg -i “$INPUT_VIDEO” -vf “subtitles=‘$SUBTITLES_SRT’:force_style=‘fontname=Arial,fontsize=28,outline=1,borderstyle=3,backcolor=&H80000000,primary_color=&H00FFFF’” -c:v libx264 -crf 23 -y /tmp/output_final.mp4

Irrefutable Evidence of the Failure:

• Input Data: The screenshot shows the Binary input to the Execute Command node is correct. Both properties (video_file and subtitles.srt) are present and valid.

• Syntax Check: The syntax used has been validated as 100% correct (using .filePath and mandatory bracket notation for [‘subtitles.srt’] due to the dot).

• Output Result: The output confirms the expressions resolve to empty strings:
  INPUT_VIDEO=“” ; SUBTITLES_SRT=“” ; ffmpeg -i “”

Has anyone running n8n on an Elestio/Alpine environment experienced this issue? If so, what was the server-side fix (e.g., a specific environment variable like N8N_TEMPORARY_DIR or a permissions change) required to get the {{$binary…filePath}} expression to correctly resolve a string?

Thank you for any insight you can provide into this deep environmental configuration bug.

[mohamed3nan]

Hi @Nick_B

I do not think {{$binary.video_file.filePath}} is correct, there’s no filePath property, and it’s clearly highlighted in red in your screenshot.

As far as I know, you need to provide FFMPEG with a valid file path that exists on disk..

So you’ll probably need to use the Read/Write Files from Disk node to write the file to disk, and then use that file path in the Execute Command node to pass it to FFMPEG commands..

Don’t forget to remove the files once you’ve generated your output.

So basically, think of it as writing and reading from the disk for FFMPEG, rather than relying on n8n’s binary references since you’re working directly with the command line.

[Nick_B]

Great suggestion buddy, it worked. Thank you!