Video files are large because they contain thousands of images (frames) per second. Compression makes them manageable without destroying quality. Here's how it works — explained simply.
What is a Video Codec?
A codec (coder-decoder) is the algorithm used to compress and decompress video. Think of it as the recipe for how video data is stored and played back.
Major Video Codecs Compared
| Codec | Compression | Support | Best For |
|---|---|---|---|
| H.264 (AVC) | Good | Universal | Sharing, streaming |
| H.265 (HEVC) | 40% better than H.264 | Good | Storage, 4K |
| VP9 | Similar to H.265 | Chrome, Firefox | YouTube |
| AV1 | 50% better than H.264 | Growing | Streaming future |
What is Bitrate?
Bitrate is the amount of data used per second of video (measured in Mbps or kbps). Higher bitrate = better quality = larger file. Lower bitrate = worse quality = smaller file.
- 1080p streaming: 4-8 Mbps (YouTube standard)
- 1080p high quality: 10-20 Mbps
- 4K streaming: 15-25 Mbps
- WhatsApp (720p): 1-2 Mbps
What is CRF?
CRF (Constant Rate Factor) is a quality-based encoding mode. Instead of setting a specific bitrate, you set a quality target (0-51 for H.264). Lower CRF = better quality. FileCurve's "High quality" mode uses CRF 23, "Medium" uses CRF 28.
Why Does Video Take So Long to Compress?
A 1-minute video at 30fps contains 1,800 frames. Each frame must be analyzed, compared to adjacent frames, and re-encoded. FileCurve uses WebAssembly to run FFmpeg in your browser — impressive technology but inherently slower than native desktop apps.