Media metadata as tibbles
In tidymedia: Media File Preprocessing and Metadata for the 'tidyverse'

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)
# Metadata readers shell out to FFprobe / MediaInfo. Chunks that need a binary
# are evaluated only when it is available, so this vignette builds cleanly on
# machines (and CI images) that lack the command-line tools.
has_ffprobe <- nzchar(Sys.which("ffprobe"))
has_mediainfo <- nzchar(Sys.which("mediainfo"))

library(tidymedia)

tidymedia reads media metadata into tibbles. So the metadata of a whole folder becomes a data frame that you can filter, join and summarize.

Two programs read the metadata:

FFprobe, used by the probe_*() functions, reads facts about the container and each stream.
MediaInfo, used by the mediainfo_*() and get_*() functions, reads a larger set of fields, grouped in a different way.

You need the program installed to use its functions. The README shows how to install them. The examples use the sample clip that comes with the package:

video <- system.file("extdata", "sample.mp4", package = "tidymedia")

Which reader?

The readers differ in the program they use and in what they return. Choose by what you need back:

| Functions | Program | Returns | Use it when | |---|---|---|---| | probe_all(), probe_container(), probe_streams(), probe_video(), probe_audio() | FFprobe | tibbles, with rows for the file and for each stream | you want the file and stream facts as a data frame | | mediainfo_query(), mediainfo_template() | MediaInfo | a tibble with one row per file | you want MediaInfo's larger set of fields as a data frame | | mediainfo_parameter() | MediaInfo | one value per file | you want one MediaInfo field for several files | | get_duration(), get_frame_rate(), get_width(), get_height(), get_sample_rate() | MediaInfo | one number per file | you want one common field without naming a MediaInfo section |

Some facts, such as the width of the picture, come from both probe_video() and get_width(). Then choose by the shape you want back and the program you have.

Probing with FFprobe

probe_all() returns a list of two tibbles. container has one row for each file, and streams has one row for each stream. Both start with a file column, so the results for several files stack into one table.

info <- probe_all(video)
info$container

info$streams

The other probe_*() functions return one part of that result. You can give them the result of probe_all(), so FFprobe does not read the file again. Or you can give them a file with infile:

# Use the probe result, so the file is not read again
probe_video(info)

By default, typed = TRUE gives number columns a number type. With typed = FALSE, every column is a string. FFprobe reports a frame rate as a fraction such as "30000/1001". The fraction stays a string, even with typed = TRUE.

Querying with MediaInfo

MediaInfo groups its fields in sections, such as General, Video and Audio. mediainfo_query() reads several fields from one section into a tibble:

mediainfo_query(
  video,
  section = "Video",
  parameters = c("Width", "Height", "FrameRate")
)

mediainfo_template() reads a whole set of fields at once. The package has two templates, "brief" and "extended":

mediainfo_template(video, template = "brief")

For one value, use the get_*() functions:

get_duration(video, unit = "sec")
get_width(video)
get_height(video)

Batching over many files

Each reader takes a vector of files, so you do not need a loop to read a whole folder. The probe_*(), mediainfo_query() and mediainfo_template() functions mark each row with its file. The get_*() functions return one value per file, in the order given.

ffm_jobs() lists the video files in a folder, in all the formats it knows. To list only one format, add extension = "mp4". If the folder has no such files, ffm_jobs() stops with an error:

files <- ffm_jobs("my/videos", type = "video")$input
probe_all(files)$container

A file that cannot be read gives a row of NA values and a warning. The other files are still read.

For a large folder, add parallel = TRUE. The files are then read in parallel with furrr. Each probe_*() function takes this argument. On the functions other than probe_all(), it has an effect only when you pass infile.

probe_all(files, parallel = TRUE)$container

The files are read in parallel only if you set a future plan. With no plan, they are read one at a time, and R gives a warning that says so. vignette("batch") shows how to set a plan.