Transloadit: PDF to Video, variable length - pdf

Question

/video/merge docs
I need a template that converts a PDF to a video. Unfortunately, the /video/merge robot seems to require both a framerate (slide length) as well as a video duration. Since I don't know how many pages the PDF will have, I'm unable to supply duration.
Is there a way around this?
This is a section of my current template:
"pdf_to_images": {
"use": ":original",
"robot": "/document/thumbs",
"format": "png",
"width": 1920,
"height": 1080
},
"encode": {
"use": {
"steps": [
{
"name": "pdf_to_images",
"as": "image"
}
]
},
"robot": "/video/merge",
"preset": "iphone",
"width": 1920,
"height": 1080,
"ffmpeg": {
"b": "8000K"
},
"framerate": "${fields.framerate}",
"duration": "100"
},
//...store...
I need to replace "framerate" from a field in the upload, but can I replace "duration" from dynamically counting the number of results from "pdf_to_images"?
Otherwise I'm stuck creating individual videos from each image result from "pdf_to_images" and then concatenating them, which seems rather excessive in terms of resource capitalization.
Thoughts?

Answer 1

What you could be looking for is ${file.meta.page_count} – which, as expected, will return the number of pages in the PDF from /document/thumbs. For example, if you wanted to make a video where each page of the PDF lasts a second you'd use a template like so:
{
"steps": {
":original": {
"robot": "/upload/handle"
},
"pdf_to_images": {
"use": ":original",
"robot": "/document/thumbs",
"format": "png",
"results": true,
"width": 1920,
"height": 1080,
"imagemagick_stack": "v2.0.7"
},
"merged": {
"robot": "/video/merge",
"use": {
"steps": [
{
"name": "pdf_to_images",
"as": "image"
}
]
},
"result": true,
"framerate": "1",
"duration": "${file.meta.page_count}",
"ffmpeg_stack": "v4.3.1",
"preset": "iphone",
"resize_strategy": "fillcrop"
}
}
}