File size limits are everywhere. Discord free accounts cap uploads at 10 MB (25 MB with Nitro). Gmail caps at 25 MB. WhatsApp allows 16 MB for standard accounts. Even cloud storage share links have download limits on some plans.
When your video exceeds these limits and compression alone cannot shrink it enough, the alternative is splitting the video into multiple parts that each fit within the size limit.
Calculating segment count and duration
The math is straightforward. You need to know your video's total file size, bitrate, and the target size limit.
Example: A 60 MB video that needs to fit in 10 MB chunks. 60 MB / 10 MB = 6 parts needed.
If the video is 3 minutes (180 seconds) long: 180 seconds / 6 parts = 30 seconds per part.
Split the video every 30 seconds to produce six segments that are each approximately 10 MB.
The approximation is not exact because video bitrate varies throughout the clip (action scenes have higher bitrate than static scenes). Some segments will be slightly above or below the target. If a segment lands slightly over the limit, trim a few seconds from it or increase the number of segments.
A faster approach: compress first, then check if splitting is still needed
Before splitting, try compressing the video. A 60 MB video compressed from CRF 23 to CRF 28 might shrink to 25 MB, which fits in a single Gmail attachment without splitting at all. Compression is less work than managing multiple parts.
If compression alone does not get the file under the limit, use compression plus splitting:
1. Compress the video to a comfortable CRF (28-30) using the MediaBrew compress tool. 2. Check the resulting file size. 3. If still too large, split into the minimum number of parts needed using the split tool.
This minimizes the number of parts the recipient needs to deal with.
How the recipient reassembles the parts
This is the awkward part. Video splitting produces separate files (part1.mp4, part2.mp4, etc.). The recipient needs to either:
1. Watch them sequentially: Open each file in order. This works for casual viewing but is annoying. 2. Merge them back: Use a merge tool to concatenate the parts back into a single file. The recipient can use the MediaBrew merge tool for this. 3. Upload to a sharing service: Instead of sending parts via Discord or email, upload the full file to Google Drive, Dropbox, or WeTransfer and share a download link. This avoids the splitting problem entirely.
Option 3 is often the best approach when available. But some situations (offline sharing, platforms without link support, contexts where you need to use the messaging platform directly) require actual file splitting.
Maintaining quality across splits
When splitting with re-encoding, each segment is independently compressed. To maintain consistent quality across all parts, use the same CRF or bitrate setting for each segment. This prevents some parts from looking better than others.
When splitting without re-encoding (stream copy), quality is preserved identically to the original because no compression is applied. The data is simply copied into separate containers.
The MediaBrew split tool lets you enter split points based on your size calculations and produces individual downloadable segments. If the recipient does not want to reassemble manually, consider compressing first (MediaBrew compress tool) or sending a cloud link instead.