No matter what the format of the original video is, the processed output video is uniformly in mp4/h264 encoding format. MP4 is a lossy compression format, so as long as re-encoding is involved, the video quality will definitely change, no matter how you modify the configuration.
The parts of the software that involve re-encoding are as follows. As long as they are used, even if you set crf to 0, there will still be some quality loss.
1: Original video is not MP4 or not h264 encoded, it will be re-encoded
This is obvious. Format conversion must be re-encoded, and MP4 is a lossy format, so the quality will definitely be reduced. In addition, even if the original video is MP4, it is also distinguished between h264 and h264 encoding. H264 is a more compatible encoding method, so the output will use h264.
If you want to maintain the original video quality, you must first ensure that the original video is an MP4 video in h264 format.
If you have installed the PotPlayer player, you can right-click "Properties" on the video playback interface to view the specific encoding method.
2: Enabling video slow motion will re-encode
Changing the video frame rate will inevitably re-encode. If you want to maintain the original quality, you need to prohibit the use of video slow motion.
3: Selecting to embed hard subtitles will also re-encode
Hard subtitles need to be written into the video screen, which naturally requires re-encoding. If you want to maintain the original video quality, you cannot use hard subtitles. You can use soft subtitles, but note that soft subtitles cannot be displayed when playing on the web, and for some playback software, the soft subtitles need to be renamed to the same name as the video and placed in the same directory before they can be displayed. Domestic players may also need to manually convert the SRT file to GBK encoding.
4: If there is an extension at the end of the video, it will also be re-encoded
After voiceover, the voiceover duration may be longer than the original video. By default, the video will be extended until it matches the voiceover duration. Extending the video requires re-encoding. If you don't want to extend, uncheck the "Extend at the end of the video" checkbox in the software interface.
In summary, if you want the video quality to have no loss, you must ensure
- The original video is an MP4 encoded with h264.
- Disable video slow motion.
- Do not embed subtitles or only embed soft subtitles, prohibit embedding hard subtitles.
- Do not select voiceover or use voiceover, but at the same time, you must prohibit extending the end of the video.
If the above requirements are not met, but you still want the video to maintain the highest possible quality, you can change crf=13 to crf=0 in the advanced options, which will minimize the quality loss during video encoding.