Film frames converted to uncompressed RGB bitmaps in huge volumes requires an uncomplicated and reliable way to make the raw material for final YUV based film masters.

This is how we do it using Adobe After Effects.

Though uniquely part of the HomeDVD HD film to video telecine process, other imaging applications that use RGB format sequences for conversion to a video stream can adapt to what is about to be presented here.

There are many stand alone utilities that will do an image sequence to HD video conversion, but they cannot handle the shear volume of frames or the HD image dimensions like Adobe After Effects can.  Adobe Premiere Pro can process image sequence to video conversions as well, but has limits in the selection of output file type and more importantly the number frames it can handle is restricted to 5000.  You would be forced to do your conversions in many chunks, making it a time consuming choice.

The first stage of the HomeDVD film to HD video workflow is to capture each film frame as an uncompressed RGB bitmap at 8 bits per pixel (we will be offering 12bits per pixel in TIF format, when we have completed our telecine system mods due in the next few months). The headend of our telecine system is set for 1440 x 1080 image size, square pixels.  That turns out to be very close to the 4:3 aspect ratio the film frames exhibit, whether they be 8mm, Super8 or 16mm film gauges.  The pixel aspect ratio by default is set to be square.  The image format chosen is the Windows BITMAP mainly for its simplicity in RGB structure. This helps greatly in timely captures and fast hard disk stores.

When initially captured by the image sensor, the digitized film frame is in its raw RGB BAYER form and is converted to a standard RGB bitmap as part of its light to digital transformation.  Each converted image is stored in a chronological sequence identified by the convention of increasing numerical values attached to a file name like img001.bmp, img002.bmp, img003.bmp and so on.  An 8mm film reel with 400ft of film frames can be around 32000 images (80 images per foot). Each film frame becomes an uncompressed RGB image of about 4.8MB in size.  So for a 400ft reel of 8mm film, about 155GB of storage is needed.

Once the film reel or reels have been captured, their converted images are usually dumped into their own image sequence folder on a hard drive. The conversion to an HD YUV AVI video file is the next step.

Open Adobe After Effects (CS2, CS3 or CS4) and give it a project name (not necessary, but useful if the project needs to be restarted for some reason). Go to the main menu at File…Import…File and select the image sequence folder to convert and the first image file to import.

Next you must create a “composition” so the image sequence block becomes part of AE’s rendering queue.  Go to “Composition” on the main menu bar and select “Add to Render Queue”.  A default name for the composition will be called “img” that matches the file prefix of the image sequence.  You will see at the bottom of the main AE interface a tab called “Rendering Queue”.  Your project settings are stored here.  Select this tab.

Here you will setup the properties of your render so that AE can compile the image sequence into the proper HD video characteristics and CODEC.

See heading “Render Settings” below the “Current Render Details” heading, and click on the corresponding blue title.  It may say “Best Settings”.

Further, there are two other settings in blue print that are prefixed by titles:

Output Module:   This will define the HD CODEC you may wish to choose.
Output to:           This will define the location and name of your rendered output file, see below:

Click on the blue text on the right of the “Output Module” title.  This resulting dialog will setup the project and provide the means to select the HD CODEC of your choosing.  Make sure the “Format” is set to Video for Windows, “Embed” is set to None and the “Post Render Action” is set to None, in the “Based on 8bit YUV 422” frame.

Some are SD in nature, so be careful what you choose.  For our purposes here we will select one of the Drastic Technologies CODECs that support YUV 4:2:2 colour spaces in 8bits per pixel format.  Select and Click OK.

If you wish to use the Drastic Technologies codecs, there is free download on the DT site Drastic Tech, or read a little background right here on our Resources page under Software – YUV Download.

Next, we must set the location and name of the rendered ouput.  As before, go to the Render Queue tab and select the blue print title beside the “Output to” heading.  Select the drive, folder and filename of the rendered file.  Be descriptive in your file naming.  It may help to keep track of differing file properties in projects with a large number of reels and end purposes.

The system is now ready to render the image sequences to the AVI YUV file format that has been selected.  On the far right of the Render Queue tab click on the “Render” button to begin the process.

Depending on the number of images to conform to YUV 4:2:2 AVI video and the performance level of your computer, expect to wait awhile for the conversion process to complete.  It can take a few hours.  Benchmark on a 2.8GHZ Core Duo, 32bit O/S, is about 2 hours to crunch a 400ft film reel of 32000 frames. Resulting files size may be in the order of about 155GB.

When the image to video conversion is complete it may be a good idea to playback the rendered video file in Windows Media Player, just to see how the conversion went.  Due to the uncompressed nature of the files — just plain huge, they will play sluggishly in Media Player unless you have a super fast computer.  But let’s assume you have a fast machine that has no trouble playing back these types of files.  You will see the YUV video play a little fast.  This is normal as the digitized film frames are playing back at the 24fps or 29.97 fps speed chosen early on in the render setup.  This speed discrepancy issue will be resolved later in the telecine conversion process when “pulldown” is applied to the YUV video stream ensuring that smooth realistic playback rates occur.