How to pull up/down audio in Nuendo

If you work in audio post and have ever had to work on a project to be broadcast on the other side of the Atlantic, you probably faced the following problem: How to convert audio files to meet the country’s broadcasting norms?

If you’re wondering what standards we’re talking about, here’s a quick summary to guide you through it :

PAL & NTSC :

    1. The Phase Alternating Light (PAL) and the National Television System Committee (NTSC) are the two main broadcasting guidelines for frame rate, image resolution and audio standards that are used around the globe. You can see on this map how these norms are used around the world.
    2. The important point to remember here is that depending on the target market for your audio/video project, there are certain considerations to be made regarding the technical specifications of the audio files.

But what is the difference between the two?

    1. Without getting into the specific technicalities, what you need to understand is that the main difference between the various broadcasting standards is related to the frame rate used. The frame rate represents the number of frames per second or FPS that is broadcasted on a screen.
    2. Here is a table expressing the FPS associated with the PAL standard and the NTSC standard.

      PALNTSC
      FPS25 (TV)29,97 (TV) / 23.978
      5060
      Movie24

If you want to go from one format to another you could:

    1. Use an external hardware clock like the Steinberg Syncstation in order to synchronize the audio with the new video and its specifications. To do so in Nuendo, you would only need to open the Project Setup and select the Audio Pull/Down drop down menu right here, and click on the correct ratio. The clock would do the job for you. But what if you don’t own this pricey piece of equipment? Well this solution won’t be of any use, since your digital workstation won’t be able to process the changes by itself.
    2. You could always time stretch your audio depending on the nature and the complexity of your project. This method can work, but it can also leave you with audio artifacts
    3. If these two methods above are not an option for you and your project, here is what you can do.There are two manipulations to do in order to achieve our goal. 
    • Audio Speed Change : First of all you have to alter the duration of the clip (using a different sample rate), referring to the chart. This way it’ll match the duration of the video that was altered to fit the desired norm. However, this step will most likely result in a change in pitch for your audio.
    • Pitch Correction : And that’s why you’ll have to readjust the pitch (by applying a pitch correction), so the audio sounds similar to the one we had on our original project.

Frame Rate Change

Audio Speed Change

Pitch Correction (if needed)

Audio speed difference (at 48Khz)

NTSC to PAL

4.1% Up

4.1% Down // 95.9% // -0.89

Semitones

50,050

Film to PAL 

4% Up

4% Down // 96% // -0.71 Semitones

50,000

NTSC to Film

0.1% Up

0.1% Down // 99.9% // -0.02

Semitones

48,048

Film to NTSC

0.1% Down

0.1% Up // 100.1% // +0.02

Semitones

47,952

PAL to Film

4% Down

4% Up // 104% // +0.68

Semitones

46,080

PAL to NTSC

4.1% Down

4.1% Up // 104.1% // +0.68

Semitones

46,034

Let’s take the example of this project, which is a European docu-serie, initially distributed in Europe, but was broadcasted on an US TV channel afterwards. You can see in our session we have different stems: music, ambiences, SFX and dialogues.

  1. Rendering the audio files in stems allows us to have more control over each audio “group”, without having to deal with hundreds of audio clips (compared to keeping our original session). 
  2. Process:
    • Select your audio clip
    • Apply a transformation to the clip itself, here in Nuendo we will click on F7 (or Direct Offline Processing), then select the Resample process here to enter the values for the desired manipulation. According to our chart, we selected the 50050 value, which gives us a 4,2% down.
    • Then, once the processing is done, select the Pitch Shifting plugin and enter the matching values (you can refer to the table mentioned earlier). Here we have to adjust our clip by 68 semitones. 
    • The process can be quite long depending on the length of your audio clip, so make sure you’ve set enough time ahead.
    • You can see there’s different algorithms available to process your clips. The option you choose depends on the stems you’re dealing with and the results you’re looking for. You’ll have to find the recipe that fits your needs and the one that leaves you with less artifacts.
    • Special mention: some plugins allow you to perform both actions at the same time. The only thing you need to make sure of is that the final result matches the length of the final video, and also, that you don’t end up with too many audio artifacts.