When the project is ready I submit it to my client for review. The client watches the video and makes his comments where the change is required. I use these comments to make the changes on a project and send new revision back to the client for his next review. In most of the cases, the changes affect only small portions of the video, however after applying them on the project, I have to render the entire video again.
Rendering entire video and waiting hours each time few frames were changed in the project makes the production very inefficient. How could the rendering part of the video production be improved? The solution is straightforward:
Image sequence rendering
I regret neglecting the sequence render, even though I knew about it for quite some time. And now I am using it as my main workflow. So when a small change is made somewhere in the project, all I have to do is to render only the frames that actually changed in the final output skipping rest of the frames. The only downside of this flow is that I have to make the render twice each time I want to produce the final video. One time is to render the project into sequence of image files (Pass 1), and the other time is to render the image files into the final video (Pass 2). But the advantage of saving so much time during production outweighs by far this little inconvenience. Besides, you can automate the process.
Why should you render in to image sequence?
The advantage of this flow is obvious. For instance, if it takes 5 second to render one frame (assuming average processing time if using multiprocessing render) then for 5 minutes video, which is around 8000 frames (depending on frame rate), the render time will be around 10-11 hours each time we render the video. However, when we make the change which affect only few hundreds of frames it will take only 10-30 minutes to render just the affected portions of the video! The only thing left to do is to render these image files into the actual video file which will take in our case less than 10 minutes to render. Thus in this case for rendering the project we are spending 1 hour or less instead of 10 hours or more!
When not to use image sequence rendering
If render time for a single frame is very short (few seconds) then you will not benefit much from this method as the second render (Pass 2) which is rendering the image sequence into the final video will take about the same time as rendering project into the video directly.
Here is how to render your heavy After Effects projects the efficient way
When your project is ready for review and the only thing left is to render the final video for the review, first thing to do is to render entire project into image sequence. That means each frame of your video will be saved in a separate image file. Later you will render these images into the final video, we’ll get into it in a minute.
There are few image formats that we can render our project into: JPEG, TIFF, PNG, Photoshop, IFF etc. I recommend using PNG format as the output file size is relatively small, using only lossless compression, it supports alpha channel (if needed) and easily viewable on Windows or Mac.
PASS 1 – Follow these steps to make the first render of your image sequence
Step 1: Add your composition into the Render Queue (Ctrl+Shift+/)
Step 2: In the Render Queue click on Output Module template name to open Output Module Settings window
Step 3: In Output Module Settings window set Format to PNG Sequence
Step 4: Click on Render Setting template name to open Render Setting Window
Step 5: Check Skip existing files (allows multi-machine rendering)
Step 6: Click on the Output file name and choose a separate folder for your image sequence files
Tip: If you have enough RAM installed in your machine, enable the multi-processor rendering for faster render!
Your project is ready for the first render! Click Render button, or hit Enter on your keyboard to start rendering.
After the first render is over you have a folder with lots of images inside. Each image represents a specific frame in the composition. Now all you need to do is to render the final video from these rendered image files.
PASS 2 – Follow those steps to render the final video from image sequence
Step 1: create a new composition, by dragging the final composition in to the Create a new Composition icon in Project Panel. You need your final composition precomposed in order to get the audio portion of the composition
Step 2: In the new composition disable the video portion of the layer by clicking on the eye icon or using Ctrl+Alt+Shft+v shortcut
Step 3: Import the image sequence into the project by navigating to the folder and selecting one of the files. Make sure PNG Sequence checkbox is checked
Step 4: In the project panel, right click the sequence object you just imported, Interpret Footage -> Main
Step 5: In the Interpret footage window set the correct frame rate of your project
Step 6: Drag the sequence into the new composition you created in step 1. It should have the exact same duration as the precomposed final composition with the audio portion of the project.
Step 7: Render the new composition in to your final video.
Tip: For After Effects CS5 and newer, use Media Converter to render your project in background which will allow you working on the project while rendering.
Now when you make changes to the project and need to render it again, you will render only the frames which were affected by the change. There are couple ways of doing it.
You could set the working area to required range and render just the frames from that area. Later when the render of new images is over, you will copy new image files (make sure you render using the same file names!) into the initial folder with the original image sequence by replacing the old files with the new ones. It is always a good Idea to back up the original images in case you get messed up with the files.
However, much easier way is to use the multi-machine rendering feature which we enabled in the Render Settings window when made the first render at step 5 by checking Skip existing files (allows multi-machine rendering) check box:
When enabled, AE will check whether the image file of current frame it wants to render is already exists (or currently being created and rendered by some other machine) and if it does, AE will skip to the next frame. With this feature enabled all we need to do is to delete the frames that has been changed in the project and let AE run through all the frames, render those portions which you have just deleted and skip those portions that you did not delete.
It is recommended to Purge -> All in order to update the sequence file in the AE project with new image files for correct RAM previewing.
Tip: If you have two or more computers you can render your project into the image sequence on shared location of your network using all of your computers. This method also known as “render farm”, “multi-machine rendering” or “network rendering”.
What is your After Effects rendering flow for heavy projects? Please share your tips in the comments below!