Batch processing

compressBatch(inputs: readonly BatchInput[], options?: BatchOptions): Promise<string[]> validates all input strings and JavaScript options first, then processes videos sequentially in an isolated session. Each input is { inputUri: string, options?: CompressOptions }. Native readability, duration, permissions, codec support, and filename collisions are checked as each item is reached.

Options are an optional signal: AbortSignal and onProgress: (event: BatchProgress) => void callback. Progress contains the zero-based index, total, fractional itemProgress, and overall progress. Aggregate progress is (index + itemProgress) / total, weighted equally per item, not by file size or duration. Returned paths retain input order.

import { compressBatch } from "react-native-media-transformer";

export async function compressVideos(
  inputUris: readonly string[],
  signal: AbortSignal,
) {
  try {
    const paths = await compressBatch(
      inputUris.map((inputUri) => ({
        inputUri,
        options: { quality: "medium" as const },
      })),
      {
        signal,
        onProgress: ({ index, total, progress }) =>
          console.log(
            `Video ${index + 1}/${total}: ${Math.round(progress * 100)}% overall`,
          ),
      },
    );
    return { status: "complete" as const, paths };
  } catch (error) {
    if (error instanceof Error && error.name === "AbortError") {
      return { status: "cancelled" as const };
    }
    throw error;
  }
}

Create an AbortController in your app, pass controller.signal to this helper, and call controller.abort() from a cancel action while it is running. Handle the helper's non-abort rejections too. cancelCompress() does not cancel a batch.

A failure stops the batch and rejects its promise, without a partial results array. Earlier completed files remain in cache; failed/cancelled temporary files are removed. Use unique output filenames per item, or a repeated fixed name can cause a collision. Manage individual session calls in the app if you need per-file recovery.

An empty batch resolves to []. A pre-aborted signal rejects before processing, including for an empty batch. When abortion is observed, the active export is cancelled, subsequent items do not start, and the batch rejects with name: 'AbortError'. A file completed immediately before abortion can remain on disk.