Regardless of the original video format, processed output videos are standardized to mp4/h264 encoding. MP4 is a lossy compression format, so any re-encoding will inevitably alter video quality, regardless of configuration changes.
The parts of the software involving re-encoding are listed below. If any of these are used, even setting crf to 0 will result in some quality loss.
1. Original Video is Not MP4 or Not H.264 Encoded, Will Be Re-encoded
This is obvious: format conversion requires re-encoding. Since MP4 is a lossy format, quality will definitely decrease. Furthermore, even if the original video is MP4, it needs to be specifically H.264. H.264 is a more compatible encoding method, so the output will use H.264.
If you wish to maintain original video quality, you must first ensure that the source video is an MP4 video with H.264 encoding.
If you have PotPlayer installed, you can right-click on the video playback interface and select "Properties" to view the specific encoding method.
2. Enabling Video Slow-Motion Will Re-encode
Changing the video frame rate will inevitably lead to re-encoding. If you wish to maintain original quality, you must disable video slow-motion.
3. Choosing to Embed Hard Subtitles Will Also Re-encode
Hard subtitles are written directly into the video frames, naturally requiring re-encoding. If you want to maintain original video quality, you should not use hard subtitles. Soft subtitles can be used instead, but note that soft subtitles may not be displayed when playing on the web. Additionally, some players require soft subtitle files to be renamed to match the video file and be in the same directory to display correctly. Domestic players might also require manual conversion of SRT files to GBK encoding.
4. Video End Extension (Padding) Will Also Re-encode
After dubbing, the dubbed audio duration might be longer than the original video. By default, the video will be extended until it matches the dubbing duration. Extending the video requires re-encoding. If you do not want to extend the video, uncheck the "Video End Extension" checkbox in the software interface.
In Summary: To Ensure No Loss in Video Quality, You Must:
- The original video is an MP4 with H.264 encoding.
- Disable video slow-motion.
- Do not embed subtitles, or only embed soft subtitles; hard subtitles are forbidden.
- Do not select dubbing, or if dubbing is selected, video end extension must be disabled.
If the above requirements are not met, but you still wish to maintain the highest possible video quality, you can change crf=13 to crf=0 in the advanced options. This will minimize quality loss during video encoding.