Peter Taps

Phil, I appreciate your help. I like ffmpeg/avconv as it runs on Linux. One problem I found was that ffmpeg does not take a 3D LUT file as a parameter. I am wondering if you know any workaround for this. I also looked at another tool called AviSynth. It has the capability to take a 3D LUT file via a plugin. However, the plugin works only on Windows. Regards, Peter

Thank you all for your help. Regards, Peter

Folks, I have to set up a process of converting dpx static images to H.264 movie file. During the process, I also need to apply a LUT for proper color conversion. DPX images are in RGB format and H.264 is in YUV format. I am being told by some people working at a digital processing lab that, in their experience, converting dpx to H.264 never gives them good color output. Instead, they convert dpx images to .mov file first. In the next step, they convert .mov file to .mp4 file. This seems to give a better color output. What I didn't get is a good technical explanation on why this works better. I am wondering if there is any merit to this approach. We don't mind going though this additional step, if required. However, I am hoping I can find a better solution that helps reduce our overall processing time. Regards, Peter

Hi Mike, Thank you for your help. I did some research on 3D LUT. I think I understand the concept now. However, I couldn't find any articles on how to go about building a 3D LUT and the parameters one should use to build the LUT. I would appreciate your help if you could point me in the right direction. The team that would build the 3D LUT would sit in the theater hall, apply the lut and view the output on the screen. They would keep modifying the LUT until the output looks right. My job is to help them simplify build the LUT. I appreciate your help. Regards, Peter

Phil, Thank you for your help. We recently got into the process of converting movie films into 1080p mp4 files. The original movie is supplied to us by the movie producer. It consists of a series of dpx images. The team that is currently doing the conversion uses Adobe Premiere to adjust colors. However, it has been a bit of trial and error. Also, the overall process takes a couple of days to complete. My responsibility is to find a better solution. I am looking at either using freeware software on Linux (such as the one from ImageMagick) or developing our own software. Ultimately, we would like to deploy several machine (one per movie reel) so that we could run the conversion process in parallel using the same settings. Hope this gives you enough background. Regards, Peter

Thank you all for your help. Mike. The link you mentioned was quite enlightening. Upon further investigation, it seems the best approach is to apply "s-curve" to the input dpx file. If I go with s-curve approach, I am trying to understand the parameters I would need. 1. Is this thinking correct? log-curve-value minus s-curve-value equals linear-value. 2. The s-curve can be simulated in multiple ways. I could use an equation such as the one mentioned in the wiki http://en.wikipedia.org/wiki/Logistic_function. Or, I could ask the user to give me a few points on the curve. What is a good approach? 3. Do I need three different s-curves for R, G, and B components? Appreciate your help. Regards, Peter

Folks, The company I work for has received a bunch of dpx image files (3TB). I have been asked to develop an application that will create a LUT that can be applied to the images for viewing on a specific projector. After doing some research on Google, here is what I have proposed: 1. Load the DPX image in Adobe Premier Pro and change the pixel colors so that they match the desired final output. 2. Give me the original DPX image and the converted image. 3. I will create a look-up table that simply matches the old RGB value to the new RGB value pixel by pixel. I am wondering if this logic would work. My area of expertise is in software development. Please forgive my limited knowledge on cinematography. One of the graphics consultant mentioned something about this strategy not working as the input dpx file is "log" formatted and not "linear." I didn't get this part either. If it is an image file, all it will have is the RGB value, either directly or indirectly, of each pixel that needs to be displayed. Thank you in advance for your help. Regards, Peter