separate_audio_video_batch: Separate Audio and Video for Many Files From a Jobs Table

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

Separate Audio and Video for Many Files From a Jobs Table

Description

Split the audio and video streams of many input files from a single jobs tibble. This is the batch (table-driven) form of separate_audio_video(), for when you have more than one file. Each row is one input that gives two outputs. The input, audiofile and videofile columns are all required. The function is a thin wrapper over ffm_batch. It turns every input row into two single-output jobs, one per stream. So a jobs table of N rows returns 2N rows, with one reproducible compiled command per stream. Each stream uses the same map and stream-copy pipeline as separate_audio_video(). The glossary in vignette("tidymedia") explains media terms such as codec, container and stream copy.

Usage

separate_audio_video_batch(
  jobs,
  audio_codec = "copy",
  video_codec = "copy",
  hardware = c("none", "nvenc", "videotoolbox"),
  fallback = FALSE,
  quality = NULL,
  audio_stream = NULL,
  run = TRUE,
  parallel = FALSE,
  ...
)

Arguments

jobs	A data frame with one row per input. It has at least an input column (source path), plus audiofile and videofile columns that name the two destinations. All three are required. Like separate_audio_video, this function derives no output paths, because the container extension of a copied stream is the instruction. That extension must match the source codec. No two destinations in a table can be the same path. That covers an audiofile and a videofile in one row, and any two across rows. The function refuses such a table before any row runs. Optional audio_codec and video_codec columns override the arguments of the same name per row. They are character, with NA to set no codec option for that stream. Rows that omit a column fall back to that argument. An optional numeric audio_stream column likewise overrides the audio_stream argument per row. There, NA keeps every audio track in that row's audiofile. A numeric quality column overrides the quality argument per row and applies to that row's videofile (see quality). Any other columns are ignored, with one exception. A reencode column, retired with the argument of the same name, is an error and not a silent no-op.
audio_codec	A string that names the encoder for every audiofile, unless jobs carries an audio_codec column. The default "copy" copies the audio stream with no quality loss. NULL sets no -codec:a. See separate_audio_video.
video_codec	A string that names the encoder for every videofile, unless jobs carries a video_codec column. The default "copy" copies the video stream with no quality loss. NULL sets no -codec:v. See separate_audio_video.
hardware, fallback	The encoder backend for every videofile and its fallback behavior. They apply to the whole batch. They are a property of the machine, not of a row, so neither is read as a jobs column. See separate_audio_video(). hardware is batch-wide, and a stream copy runs no encoder. So a hardware other than "none" conflicts with any row whose video codec resolves to "copy". That includes the default. So split a jobs table that mixes copied and re-encoded video into separate calls. Resolving a hardware backend asks this FFmpeg build which encoders it has. So the first such call that re-encodes the video runs FFmpeg while the command is built, even under run = FALSE. The answer is remembered for the rest of the R session. See refresh_ffmpeg_capabilities to discard it. This function checks that the encoder is available before any row runs. So an unavailable encoder aborts naming this function, not the internal step that runs the rows. A call can also contradict itself by asking for GPU encoding alongside a stream copy. Such a call is refused for the contradiction first, whether or not this machine has the encoder. The stream-copy conflict above is caught first, so such a call aborts without asking FFmpeg.
quality	A number, or NULL (default), applied to every videofile unless jobs carries a numeric quality column. In that column, NA leaves that row's encoder default in place, whatever the argument says. The value is the encoder's own rate-control value, passed through unchanged. Each cell is checked against the encoder its own row resolves to. A wrong cell is refused before any row runs, and the error names this function and the row. See separate_audio_video() for the encoders, their flags and ranges, and the values it refuses. The audiofile never takes it. A cell on a row whose video codec is "copy", the default, is refused, because no encoder runs.
audio_stream	The audio track to write to each audiofile, 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) keeps every 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 every-track family reads NULL as every audio track: separate_audio_video, standardize_video, anonymize_video, crop_video, segment_video and format_for_web, and their _batch forms. The first-track family reads it as the first audio track only: extract_audio, convert_audio and normalize_audio, and their _batch forms. A container that holds several audio streams (.mka, .m4a) gets them all. A container for one stream only (.aac, .mp3, .wav) makes FFmpeg fail, so name a track to write one of those. Count only the input's audio streams. Do not use the index column of probe_audio, which counts every stream. An input with no audio at all is an FFmpeg error here, because this function writes an audio file. Functions that write only a video file, such as standardize_video, do not fail in that case. videofile is never affected. 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

A tibble with two rows per input, one per stream. It has the reshaped input, a single output path, a stream marker ("audio" or "video"), and an added command column. When run = TRUE, it also has a success column. A run also gives verified and the provenance manifest, each when requested via .... When jobs supplies either codec column, a single codec column carries each row's resolved encoder for its own stream (NA where none is set). When audio_stream is supplied as either the argument or a jobs column, an audio_stream column likewise carries each row's resolved track. That is the selected index on an audio row. It is NA on every video row, which takes no audio, and on an audio row that named no track. So NA does not by itself mark a video row. Read the stream column for that. The columns match the output of the other _batch functions, plus the stream marker. See ffm_batch.

Failed audio outputs

A row whose audio command does not finish cleanly is recorded as success = FALSE, and the batch does not abort. One warning for the whole batch, emitted once, names such rows. It lists every affected input row and the ways out.

A row reaches that warning only when all four of these hold:

• It named no audio_stream.

• The row is recorded success = FALSE.

• Its input carries more than one audio track.

• The extension of its audiofile is not among the containers named here as holding several audio streams.

Those containers are .mka, .m4a, .mp4, .mov, .mkv, .webm, .ogg, .opus and .ts. No exit status is among those conditions, and the difference from separate_audio_video is deliberate. The batch runner records whether a row succeeded and not how. So it records a non-zero exit, a hard error and a reached limit the same way. It treats alike a row put here by any of them. The nine are an exclusion list and not a survey. FFmpeg writes several audio streams into other containers too, .avi and .nut among them. A row that fails on one of those is still named. The container condition keeps a row off the list when it already does what the warning advises. Such a row is silently not named. A batch whose failed audio rows all write to those nine does not warn at all. The headline count follows the rows actually named.

Each bullet of the warning states what that row did: its track count, and that every track was mapped into one output. It never states why FFmpeg refused. Several causes look alike from here. Examples are a stream copy into a container that will not hold the source codec, an unknown encoder and a missing output directory.

The check runs FFprobe on the failed rows only. So the function emits the warning when FFprobe is available and the input can be probed, and skips it silently otherwise. The warning may not appear, and its absence is never itself a second failure. The check never runs under run = FALSE and never changes any compiled command. Suppress the warning with suppressWarnings(classes = "tidymedia_multitrack_separation").

The warning names the same event as the error of separate_audio_video and answers to the same class. But it carries no exit status: no tm_status field, and no tidymedia_ffmpeg_exit class. The batch runner records, per row, whether the row succeeded, not how FFmpeg exited. The success column holds that record. So the exit number is gone by the time this warning is assembled. To catch a specific row's exit status, use separate_audio_video().

See Also

separate_audio_video(), the one-file function it wraps. ffm_batch(), the batch runner. has_hardware_encoder() for the hardware argument. segment_video_batch() for the other batch function where one input file can give several outputs.

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_audio_batch(), 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(), 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(), extract_audio_batch(), 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(), standardize_video(), standardize_video_batch()

Examples

video <- system.file("extdata", "sample.mp4", package = "tidymedia")
jobs <- tibble::tibble(
  input     = c(video, video),
  audiofile = c("a1.aac", "a2.aac"),
  videofile = c("v1.mp4", "v2.mp4")
)
# run = FALSE compiles two commands per input without calling FFmpeg
separate_audio_video_batch(jobs, run = FALSE)

tidymedia documentation built on Oct. 11, 2026, 5:08 p.m.