I am trying to edit a video with chroma for my game, and I need to export it in VP8 format with alpha, so I export it in “WebM VP8 with alpha channel” format.
I’ve tried many different combinations of values (bitrate, GOP, B frames, etc.), but the video always exports with blurring. Here you can see the two videos, the original and the edited one: https://www.filemail.com/d/bqvvvsmoybpgwar
I also noticed that if I changed the Rate Control to Quality-based and set the Quality to 100%, it gave an error and did not export the video. In fact, I couldn’t raise it much above the base value (55%) without getting an error.
I’m including the two images here, unedited and edited, so you can see the sharpness of the original video.
I need to export it in this VP8 format with alpha, maintaining the original quality and reducing the size as much as possible. Can you help me? What values should I use when exporting?
I hope you can help me because I’ve tried many things and I don’t know what to do.
The original is 3840x2160 but the exported is 1920x1080. That is going to soften two ways: first by scaling and then by compression.
Your export is also 25 fps whereas the original is 60. This suggests to me that you relied upon Automatic Video Mode, which shows this warning in the middle of the window every time you start Shotcut.
Changing Video mode in the New Project section does not do anything until you click Start to create a project folder. If you do not that, it uses Settings > Video Mode.
You’re right, I hadn’t noticed that message. I set it to 60 fps and also exported it to 3840x2160 to see if that was the problem, but it still loses quality and remains blurry.
It will always lose quality because it is being re-compressed, and VP8 compression is lossy. However, you can use VP9. Start with the VP9 with Alpha preset, go into Advanced > Other. Remove qmin and qmax lines, and add a line lossless=1
The problem is that I cannot use anything other than VP8, because I need the videos to use in a game I am developing in Unity, and in that engine, the only format compatible with all three operating systems (Windows, Mac, and Linux) is VP8. Furthermore, I need them to have alpha.
I told you Video Mode and even explained where it lives in 2 places!
You need to think a little more outside of your specific problem at hand. This is not simply a transcode tool. It can deal with more than one video at a time, each of which can have a different resolution. The tool does not deal with everything in relative terms and values. You need to configure something like a canvas size. That is video mode. If you do not, it renders to video mode and then Export scales to whatever you put there that is different.
To continue with VP8, return to that preset, and in Other remove minrate and maxrate, change qmin=0. Now, you can experiment with different quality % or bitrate. The % change did not do anything for me, but 200M gave me a substantially larger file.
Oh yes, but I already did that Video Mode thing. I did what you told me, that’s why it exported at 60fps and 4k, right? You can see it in the filemail link I posted in the message above. It’s a video called ‘test’ that’s exported at 4k and 60 fps.
(I don’t want to repost it in this message because I don’t want the thread to be hidden again for spam.)
What is the size of your file? Mine, based on your Original.webm, is 181 MB. If you get roughly the same, I think all you can do is increase the bitrate more. However, a video quality measurement tool tells me that the exported 200M video is already 99.3% similar to the original. I see no visible difference in sharpness between the 2.
I used Average Bitrate, not Constant or Constrained VBR.
It exports it to me at 142 MB, but maybe that’s because I remove parts of the beginning and end of the video so that it loops.
I don’t know if I’m doing something wrong (which is possible), but even when I increase the bitrate to 200M, there is still some loss of quality, although it is very slight, and it looks better than before. I’ll keep testing to see if I can maintain this new quality, which is better than the previous one, and reduce the file size as much as possible.
If you send me the video you exported, I can see if it looks the same as the one I exported.
In any case, thank you very much for your help.
By the way, the software is really great. As soon as I can, I’ll donate some of my limited funds because you’ve done a great job.
There was another recent thread where someone wanted to export a WebM at an unrealistic low bitrate and should have been able to get close but did not. Between that and this thread, I learned we need to change the WebM presets to be more flexible by removing some of the constraints in Other. They have been around for many years with very little feedback until the past few days.
I am glad to hear that my issue has helped improve the software. For now, I’m using VP8 because it’s the only one Unity supports, but in the future, if they add support for VP9, I’ll use that one, because I’m sure it reduces file size more while sacrificing less quality than VP8.
Hey, one more question. What software do you use to measure the loss of quality between the original video and the exported one? I am interested in reducing the size of videos as much as possible while losing the least amount of quality.
Shotcut’s Properties menu has Measure Video Quality. Open the original video, access that menu, it opens a file dialog. Choose the exported. It creates a Job. When the job ends double-click it for a report. Scroll down to get the summary VMAF score. You can consider it as a % where a 6% difference is considered a “just noticeable difference.” However, that is more about like streaming to TV. The report also contains SSIM and PSNR scores for each frame. For a quick scan, view the SSIM of the luma (Y) channel.
You can also right click a completed Export job and choose Measure Video Quality. This compares the export with the current project. Do not use it if you changed the project since the export. It creates a report with SSIM and PSNR but not VMAF.
For now, I’m using VP8 because it’s the only one Unity supports, but in the future, if they add support for VP9, I’ll use that one, because I’m sure it reduces file size more while sacrificing less quality than VP8.