Extract Audio From Many Files From a Jobs Table

Take the audio track out of many input files, using one jobs table. This is the batch form of extract_audio(), for when you have more than one file. Each row is one input. The input and output columns are required. The function is a thin wrapper over ffm_batch. It builds one reproducible command for each input, with the same steps as extract_audio(): select the audio track and drop the video. The glossary in vignette("tidymedia") explains media terms such as codec, container and stream copy.

Usage

extract_audio_batch(
  jobs,
  audio_codec = "copy",
  audio_stream = NULL,
  run = TRUE,
  parallel = FALSE,
  ...
)

Arguments

jobs: A data frame with one row per input. It needs at least an input column (source path) and an output column (destination path). The output column is required. Unlike the video batch functions, this function cannot name an audio destination for you, because the extension is the instruction. The extension picks the container, and with audio_codec = "copy" it must match the source codec. An optional audio_codec column overrides the audio_codec argument per row. Rows without a value use the argument. NA in a cell leaves that row's codec unset, which is the column form of audio_codec = NULL. An optional audio_stream column overrides the audio_stream argument per row in the same way, and NA keeps that row on the first audio track. The function refuses two rows with the same output path, before any row runs. The function ignores any other columns.
audio_codec: The audio codec applied to every row, unless jobs has an audio_codec column. In that column, NA in a cell leaves that row's codec unset. "copy" (default) copies the audio stream with no quality loss. Name an encoder (e.g. "aac") to re-encode. Or pass NULL to write no -codec:a, so the output container's default encoder decides.
audio_stream: The audio track to take, as a number that counts from 0 among the audio tracks of each row's input. 0 is the first audio track and 1 is the second. Other streams in the file, such as video, do not count. NULL (default) takes the first audio track. Without an audio_stream column, the argument applies to every row. An NA cell in that column means NULL for that row. It does not fall back to the argument. The first-track family reads NULL as the first audio track only: extract_audio, convert_audio and normalize_audio, and their _batch forms. The every-track family reads it as every audio track: separate_audio_video, standardize_video, anonymize_video, crop_video, segment_video and format_for_web, and their _batch forms. A track the input does not have gives an FFmpeg error, not an R one. See audio_stream for how this differs from audio_input, the input index on compare_videos and picture_in_picture. (default = NULL)
run: A logical: run each command through FFmpeg (TRUE, default) or only compile them for inspection (FALSE).
parallel: A logical: process the jobs in parallel with furrr (TRUE) or one at a time (FALSE, default). See ffm_batch for the future plan requirement.
...: Additional arguments forwarded to ffm_batch (e.g. verify, manifest, progress).

Value

The jobs tibble with an added command column. When run = TRUE, it also has a success column, plus verified or a provenance manifest, each when requested through .... See ffm_batch.

Details

When a row names no audio_stream and its input has tracks that the output will not carry, the function warns once for the whole batch. The warning names every affected row. The check costs one FFprobe call per distinct input it has to probe. A repeated input is probed once, and a row that names a track is not probed at all. The warning is given when FFprobe is available and the input can be probed. Otherwise the check is skipped silently. Those probes run one at a time, before any row starts, so parallel does not reach them. A sweep long enough to look like a hang reports its progress. The check never runs under run = FALSE, never changes any compiled command, and is skipped entirely when every row names a track. Suppress it by class with suppressWarnings(classes = "tidymedia_dropped_audio").

To switch the check off and skip the whole sweep, use options(tidymedia.check_tracks = FALSE) for the session. Use withr::local_options(tidymedia.check_tracks = FALSE) for the rest of one function.

Other task functions: anonymize_video(), anonymize_video_batch(), compare_videos(), compare_videos_batch(), concatenate_videos(), concatenate_videos_batch(), convert_audio(), convert_audio_batch(), crop_video(), crop_video_batch(), extract_audio(), extract_frame(), extract_frame_batch(), format_for_web(), format_for_web_batch(), normalize_audio(), normalize_audio_batch(), picture_in_picture(), picture_in_picture_batch(), sample_frames(), sample_frames_batch(), segment_video(), segment_video_batch(), separate_audio_video(), separate_audio_video_batch(), standardize_video(), standardize_video_batch(), strip_metadata(), strip_metadata_batch()

Other audio selection functions: anonymize_video(), anonymize_video_batch(), audio_stream, compare_videos(), compare_videos_batch(), convert_audio(), convert_audio_batch(), crop_video(), crop_video_batch(), extract_audio(), format_for_web(), format_for_web_batch(), normalize_audio(), normalize_audio_batch(), picture_in_picture(), picture_in_picture_batch(), segment_video(), segment_video_batch(), separate_audio_video(), separate_audio_video_batch(), standardize_video(), standardize_video_batch()

Examples

video <- system.file("extdata", "sample.mp4", package = "tidymedia")
jobs <- tibble::tibble(input = c(video, video), output = c("a.aac", "b.aac"))
extract_audio_batch(jobs, run = FALSE)
#> # A tibble: 2 × 3
#>   input                                                        output command   
#>   <chr>                                                        <chr>  <chr>     
#> 1 /home/runner/work/_temp/Library/tidymedia/extdata/sample.mp4 a.aac  "-y -i \"…
#> 2 /home/runner/work/_temp/Library/tidymedia/extdata/sample.mp4 b.aac  "-y -i \"…

Usage

Arguments

Value

Details

See also

Examples