25 to 24fps Workflow - Using ProTools 11HD, Premiere Pro CC And Avid X-Form

05-06-2014 03:47 PM

Community member Alan Sallabank offers this contribution and gives an extensive workflow tutorial on 25 to 24fps - Using ProTools 11HD, Premiere Pro CC And Avid X-Form (or how to make a 25fps mix work for DCP without making it sound like it’s being gargled).
Doing a lot of short form trailers, but also being involved in the world of co-productions and film finance, I increasingly get asked to deliver mixes in a variety of frame rates, all at the same pitch, to a variety of audio specs.
We can sort this all out, and even allow the client to review and adjust the new mix at 24fps, even though the cutting room can only supply you with a 25fps video and AAF.
This article covers how I use ProTools 11HD, Premiere Pro CC and Avid X-Form to convert mix sessions from one frame rate to another while maintaining sync and pitch. This particular example shows converting from 25fps to 24fps, but other conversions are possible using the same technique.
First we start with our session. This is a fairly simple 5.1 mix of a trailer cut at 25fps. It needs to be delivered in 5.1 for DCP 85LEQ(m) and for internet distribution. DCP can only be delivered at 24fps, so we already have a problem.

Note the session setup:

Trim your session (audio and video tracks) to the first frame (usually on the hour) and change your session start time to match.
Once you’re happy with your original mix, save it and create a new session:

Change the session setup to 24fps and change the session start time to the same timecode as in the 25fps session:

Then select Import Session Data from the file menu:

And select the original 25fps session:

Once in the Import Session Data window, tick “Apply SRC” and use the menu to navigate to the “Pull Up/Down” settings. Select the one appropriate to your task – in this case “46,080 – 4% Down (PAL to Film)”.
Don’t select the video track as it will change your session settings, but do import its audio guide track and all other tracks in the original session.

Which will leave you with a full session, automation adjusted, clip gain in the right places, but running 4% low in pitch:

Before we address the pitch, it would be good to check the sync.
This means we have to save our project for the moment, and fire up Adobe Premiere Pro.

Start a new project

I use my nice powerful NVidia Cuda GPU to churn video, but feel free to use whatever hardware you have to hand.

Create a new Sequence in PP, and set it up according to your workflow. I run everything as Avid DNX36 8bit, 1920 x 1080, in this case at 24fps.

You can then drag your 25fps video on to the sequence timeline (ignore the clip mismatch warning and select “keep existing settings”)

We now need to make this video clip into 24fps speed. At the moment it is a 25fps video running on a 24fps timeline.

Right-clicking on the clip brings up a menu, and on that, select “Speed/Duration”

24fps is 4% slower than 25fps, so set the speed to 96%.
If you are doing a more complex conversion, you can use the duration of the video clips guide track in your new ProTools session, to tell you what duration the new video clip should be. For this exercise it’s a round number.
We now need to export this media for ProTools to import.

Again, adjust video settings to suit yourself, and select where you want to save your new video.
The result – a “24fps” video running in a 24fps ProTools session, with all the clips separate and adjustable, and the mix tweakable to take account of the new running speed and duration.

Everything is now in sync and tweakable. However the pitch is now all 4% lower. I use Avid X-Form to sort this out.

Again, because 24fps is 4% slower than 25fps, we need to raise the pitch by 4%.
For speed I usually select blocks of adjacent clips and make them into a continuous file. If you select multiple clips and try to process individually, X-Form will switch into “mono” mode, where it processes each mono leg individually, rather than in phase coherent pairs (or more). In stereo or surround it is important to maintain phase coherency.

This can be a bit time consuming, but if you require full tweakability I’d process each clip individually.
However, it is massively worth it. When any TCE software has to timeflex or pitch shift a mixed track, it is never going to be able to do as good a job. When you pitch correct all the components that make up that mix however, each clip is processed according to its content, so the quality improves.
Most times it is completely undetectable that the new mix was ever originally at a different speed. There is no “burble”, and most importantly you are able to adjust the mix to be within loudness spec, and also give the client a preview of how their mix will sound at the correct playback rate. A change of 4% makes a huge difference to the pace, and quite often the mix could do with tweaking.
I have used this technique in situations where for example, I’ve been asked for a 23.98 Internet mix in 5.1 and stereo, but also with 25fps R128 compliant stereo, with 12frame mutes, with different voice over tags. The only way to handle all these requirements and maintain consistency between the spots over different mediums, in my opinion, is to do this.
Using PT11HD, I can even bounce out a Quicktime with an embedded 5.1 or stereo mix for the client to review, before they go into online. They can preview how their mix sounds and how their cut feels at the new frame rate, before it’s all too late.
It also means that differing delivery requirements can be easily accommodated.

Disclaimer – I am no expert with Premiere Pro. However it does appear to be intuitive enough that if you know what you want to achieve, it is possible with a little knowledge, without resorting to RTFM.
If you know PP better than I do, and know more elegant, faster ways to achieve this, please let me know. Also with X-Form, if you know an elegant way to deal with the continuous / individual clips and mono / multi input mode problem, please also give me a shout!
Equipment Used

  • ProTools 11.1.3 HD (Motu Hardware)
  • Intel i7 2700 oc’d to 4.5GHz, Hyperthreading enabled, 16GB RAM, SSD, running Windows 7 Pro 64bit
  • Nvidia GTX660Ti Cuda GPU feeding three 1920x1080 monitors, over DVI and HDMI
  • All media runs over gigabit ethernet from my Synology NAS. No spinning platters in the host system.
  • Avid Artist Control (Eucontrol 3.1.2) and Neyrinck V-Control on an iPad2

Plug-ins Used

  • Izotope RX3
  • Izotope Insight
  • Waves L3LL
  • Waves UM6
  • Waves WLM+
  • Metric Halo Channelstrip
  • Avid Space
  • Avid Revibe
  • Avid X-Form
  • Avid Pro Limiter & Pro Compressor
  • Sonnox Inflator
  • ZPlane PPMUlator XL

Alan Sallabank is Dubbing Mixer, Sound Editor, ADR / Foley Recordist, Consultant and the owner of 8db Sound Ltd. You can find out more about his work here
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