Is Lossless Cut Actually Lossless?

When working with video editing software like Blackmagic Design DaVinci Resolve, it's essential to understand how lossless cutting works. The question on everyone's mind is whether lossless cut actually means no loss of quality or just almost lossless.

In a recent discussion, Pengfei Hao asked if it's possible in Resolve to rough cut a video and then trim it without changing its encoding, making the original file smaller. This raises an interesting point about the nature of lossless cutting.

According to the Resolve v17 reference manual, Chapter 46 provides detailed information on Media Management. In this chapter, you'll find that when using inter-frame codecs like H264, lossless cutting may not be able to trim to the exact frame specified. Instead, it may need to copy a few extra frames as well.

However, this doesn't necessarily mean that the quality of the original file is compromised. Lossless cut in Resolve allows you to trim your video without re-encoding it, which means that no data is lost during the trimming process. The resulting trimmed files will be identical to the originals, except for the reduced length.

To use lossless cut in Resolve, follow these steps:

1. Go to File > Media Management.

2. Select the media file you want to trim and drag it to the timeline.

3. Trim the file to the portion you want using the trimming tools.

4. Make sure the timeline is set to the same resolution and FPS as the media.

5. Use the 'Copy' command with the option 'Used media and trim keeping X frame handles.'

This process will create a copy of each file, trimmed to the specified portion, plus any handle frames if you've specified those. You can also choose to relink the project to the new files by ticking the 'Relink to new files' checkbox.

In summary, lossless cut in Resolve is not actually lossless in the classical sense, as it may need to copy extra frames when using inter-frame codecs like H264. However, this process does not compromise the quality of the original file, and you can use it to trim your video without re-encoding it.

Is losslesscut actually lossless