Making high quality movies in CFD-Post
 

Hi All,

I am trying to make an animation in CFD-Post, but for some reason my animation frame quality degrades after the first frame. Here is the link to the video:https://youtu.be/DoNFAGYfKtQ

Notice how the quality degrades as the video progresses? Not sure what I am doing wrong. I tried changing the quality and frame rate to no avail. My current settings are shown in the attached images.

Attachment 81354

Attachment 81355

I have tried searching online and on this forum without much success. Any help is appreciated, time is of essence, so if someone could help me soon that would be awesome!!

Thanks
D.B.

Edit: I realize the Youtube video might be of low quality, so attached are the screenshots of the first and last frames of the video.

Attachment 81356

Attachment 81357

Don't export to video directly. Instead, export images, and stitch them together using software like ffmpeg.

Thanks! I think that is the best way, although I am curious as to what is the reason behind the low quality when making a video directly :rolleyes:

Only the folks who implemented this will know. Probably not even them, because if they did, they would have done it differently. Don't get me wrong, you can produce similarly crappy results with ffmpeg, starting from perfectly good still images. Constant bitrate is a big one to avoid, and probably one of the culprits here. Use CRF instead.
But they are in good company. I have not come across any post-processing software that can create videos directly with acceptable quality.

External Program of course would be best, but if trying to export the movie directly from post, there are a few things you can try.

I believe the quality is bitrate limited, so high resolution and high frame rate will lower the quality. Moving the animation quickly will also hurt the quality as it can't be as efficiently compressed.

Things to try:
Set MPEG to custom instead of high, uncheck variable bitrate, and turn it all the way up 10000000.
Use 24 frames per second instead of 50. Only half the information is required and 24 is sufficient.
Lower the resolution.
I use PPM instead of JPEG, but don't know if that matters or not.
You may want to use a solid white background, though this may not do anything.

Thanks Eric,

Will try it and update with the results

I have played with MPEG settings over and over and often had problems with it. I have had much more success with Flash format. If MPEG does not work for you, try Flash.

Another advantage of exporting images: You only have to do it once. If you are not satisfied with how the video looks afterwards, you change the settings of your video encoder, and have your new video in a matter of seconds. With full control of what is going on, eliminating the guessing. Instead of running the whole post-processing again, and hoping for a better result.
I could go on, but I think you get my point by now: exporting the video directly is the inferior solution in every possible way.

Agreed, I think I am never going back to exporting just videos, the quality is drastically different, I think it is the compression in the back-end which is the issue over here, the programmers tried to get away with compressing the subsequent frames a bit more than the first frame.

Also the video playback speed, you have so much more control to accelerate and decelerate individual portions of the video, like showing in normal speed and then suddenly showing in slow-mo to emphasize a point.

My experience is that wmv-format is quite okay wrt quality. Controlling speed is however undoable. Therefore I always export the picture to a separate folder and convert these to an animation. For this I use Fast Movie Processor.

I tried to find it to no avail. Can you send me a link where I can download this?

Hi,

I actually took some suggestions from the post and compiled my own movie from the individual frames and it worked. I think there is an inherent compression in ANSYS when it makes videos, so using the individual frames does work.