FFMPEG Vstack Filter

Transloadit
1

Hey Transloadit Community,

Having some serious difficulty with utilizing Vstack to stack two videos on top of one another using transloadit.

Currently the assembly takes two videos as input, crops them to different height (but same width), and then I’d like to take those two videos and stack them vertically on top of one another. it will be two instances of the same video so the audio from either video will be valid.

Any help would be greatly appreciated.

Code:

{
  "steps": {
    ":original": {
      "robot": "/upload/handle"
    },
    "imported_video": {
      "robot": "/http/import",
      "url": "${fields.video}"
    },
    "resized": {
      "use": ":original",
      "robot": "/video/encode",
      "result": true,
      "ffmpeg_stack": "v4.3.1",
      "height": 567,
      "resize_strategy": "crop",
      "crop": {
        "x1": 922,
        "y1": 744,
        "x2": 1920,
        "y2": 1000
      },
      "preset": "web/mp4/1080p",
      "turbo": true,
      "width": 998
    },
    "resized2": {
      "use": "imported_video",
      "robot": "/video/encode",
      "result": true,
      "ffmpeg_stack": "v4.3.1",
      "height": 756,
      "resize_strategy": "crop",
      "gravity": "center",
      "preset": "web/mp4/1080p",
      "turbo": true,
      "width": 998
    },
    "stacked": {
      "use": [
        {
          "name": "resized",
          "as": "video_1"
        },
        {
          "name": "resized2",
          "as": "video_2"
        }
      ],
      "robot": "/video/encode",
      "result": true,
      "preset": "empty",
      "ffmpeg_stack": "v4.3.1",
      "ffmpeg": {
        "filter_complex": "[v1][v2]vstack"
      },
      "turbo": true
    }
  }
}

Additionally here is the error being thrown after an attempted run.

Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/srv/shared/tmp/scratch/c56e5bd91d36472f8d9bc2bcba7669f1_10810d3a670a4498b2cd1c0e17acf289': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2avc1mp41 encoder : Lavf58.45.100 Duration: 00:00:39.47, start: 0.000000, bitrate: 587 kb/s Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 998x256, 491 kb/s, 24.90 fps, 25 tbr, 90k tbn, 50 tbc (default) Metadata: handler_name : VideoHandler Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 90 kb/s (default) Metadata: handler_name : SoundHandler [AVFilterGraph @ 0x757f80] No such filter: '' Error initializing complex filters. Invalid argument