Playing back a video file using graphics cards (Windows only)

Multi-head graphics cards which support overlay functionality can be used to display the video picture on an external TV or computer monitor in full screen mode. As of this writing, the manufacturers nVIDIA and Matrox have working solutions available. Check the card’s documentation for information on how it handles video output and how to set it up for multi-monitor display.

Playing back a video file using video cards

Video cards can also be used to display the video on an external TV or computer monitor. As of this writing, e.g. the “Decklink” card (Blackmagic) can be used. For further information, check the documentation of the video card.

Video playback preferences

In the Preferences dialog (Event Display–Video page), there are two options for video playback:

• Show Video Thumbnails.

When this is activated, thumbnail frames of the video contents are shown in the track.

• Video Cache Size.

This determines how much memory is available for video thumbnails. If you have long video clips and/or work with a large zoom factor (so that many frames are shown in the thumbnails), you may have to raise this value.

Replacing the audio in a video file

Nuendo has a special function for replacing the audio in a video file:

1.Pull down the File menu and select “Replace Audio in Video File”.

2.In the file dialog that appears, locate and select the video file on your hard disk, and click Open.

A new file dialog appears.

3.Locate and select the audio file that you want to insert into the video file, and click Open.

The audio is added to the video file, replacing its current audio track (if any).

• By combining the functions “Extract Audio”, “Export Audio Mixdown” and “Replace Audio in Video File”, you can create a complete audio track for a video file.

Project window and Browser editing operations

Video clips are played back by events just as audio clips are. You can use all the basic editing operation on video events, just as with audio events. The following operations are not possible on the video track:

•Drawing, Gluing, Muting and Scrubbing.

•The video track has no editor and does not make use of parts.

Pool operations

For information about operations on video clips in the Pool, see the chapter “The Pool” on page 296.

The Edit Mode

Video playback follows the Nuendo transport, so that the video frame at the current project cursor position is shown, during playback and in Stop mode (e.g. if you move the project cursor manually or use fast forward/rewind). Nuendo has a special Edit Mode that makes use of this fact, allowing you to edit audio while getting continuous visual feedback on the video display:

•If you activate “Edit Mode” on the Transport menu, the project cursor will automatically follow when you make selections or perform editing operations (such as moving, resizing, adjusting fades, etc.).

Since the video automatically follows the project cursor, you will instantly get a visual feedback when you edit! This makes it very easy to e.g. move an audio event to a certain spot in the video.

•To avoid obscuring the view, the project cursor will be hidden from the event display in Stop mode if Edit Mode is activated.

However, it will still be shown in the ruler.

Listed below are three examples of how you can use Nuendo’s Edit Mode for matching audio and MIDI to video.

Adjusting the position of the audio event

1.If required, set the snap point in the audio event so that it identifies a significant point in the audio recording.

This would be the position in the audio that you want to match to a certain position in the video. If you don’t set the snap point, the start of the audio event will be used instead.

2.Activate Edit Mode on the Transport menu.

3.Select the audio event.

The project cursor position is automatically moved to the position of the snap point.

4. While watching the video display, move the audio event towards the correct position.

Since the project cursor automatically follows the snap point position and the video automatically follows the project cursor, you just need to move the event until the desired video frame is displayed!

Adjusting the length of the audio event

If you have a video section and an audio event for it, that doesn’t quite fit, you can use time stretch to change the length of the audio:

1.Use the method described above to position the start of the audio event at the correct position according to the video.

2.In Edit Mode, select the Range Selection tool and double-click in the audio event.

This creates a selection range that spans the whole audio event.

3.Click the right edge of the selection range and drag to adjust it to the desired length.

While you are dragging, the project cursor position follows the right edge of the range, allowing you to pinpoint the desired end position in the video.

4.Use “Locators to Selection” (on the Transport menu) to set the locators to the selection range you just made.

5.With the Arrow tool, select the audio clip to be stretched.

6.On the Audio menu–Process submenu, select “Time Stretch”.

7.Click the “Use Locators” button.

The time stretch ratio is set up so that the audio event will fit the locator range.

Make sure you don’t exceed the 75% to 125% limit!

8. Make the desired settings and click Process.

The audio is stretched or compressed to fit the range.

Creating fades

If you want the audio to fade in, reaching full volume at a certain position in the video, and fade out at another position, here is a quick way of achieving this:

This assumes that the audio event is already positioned and sized correctly according to the video.

1.In Edit Mode, select the Range Selection tool.

2.Make a selection range in the audio event, roughly covering the section that should be played at full volume.

3.Click and drag the edges of the selection range so that they exactly correspond to the end of the fade-in and the start of the fade-out, respectively.

While you are dragging, the project cursor position follows the edge of the range, allowing you to pinpoint the desired fade-in and fade-out position in the video.

4.Pull down the Audio menu and select “Adjust Fades to Range”.

The fade-in and fade-out handles of the audio events are automatically adjusted.

Ö When using the Fades handles of an audio event in Edit Mode, the cursor will follow their position as well, allowing you to adjust fades to picture in this manner.

Working with film transfers

Frame rates

Since Nuendo has been created from the ground up as a total media production system, it must be capable of working with all different types of video and film frame rates.

Standard frame rates

There are several frame rate standards in use today. They are as follows:

•23.98 frames per second (23.98 fps) used for cinema film to NTSC transfer.

•24 frames per second (24 fps) used for cinema film cameras.

•25 frames per second (25 fps) used for PAL/SECAM video signals.

•29.97 frames per second (29.97 fps) used for NTSC video signals.

•30 frames per second (30 fps) historically used for black and white NTSC video signals. This frame rate is often used in:

1)Music recording as a reference for synchronizing audio recorders and MIDI sequencing devices.

2)Most field recorders also use 30 fps SMPTE during film shoots at 24 fps so that after a 2-3 pull-down is performed for NTSC video transfer, the frame rate becomes 29.97 fps.

Film transfers

When working with film projects, video post-production editors typically transfer the film footage to video for use with computer video editing systems. Once the film has been edited, it can be transferred back to film for presentation in theaters or may remain in video format for television broadcast and release on videotape or DVD.

Pull-up and Pull-down

When film footage is transferred to video, the frame rate must be converted from 24 fps to either 25 fps (PAL/SECAM) or 29.97 fps (NTSC). This process introduces a slight speed change as a result of the mathematical relationships between the different frame rates.

The film to NTSC conversion is done as 2-3 pull-down and the film is running at 23.98 fps to maintain the exact 2-to-3 relationship. (Result: The film is running ~0.1% slower in NTSC TV.)

The audio recorded along with the film must also have these speed changes applied to it in order to remain in sync with the picture once it has been transferred to video. Sometimes the speed change is applied at the same time as the film transfer and is recorded directly on the videotape. This allows the video editor to hear the audio along with the transferred video while editing.

These speed changes also result in pitch changes. Other artifacts can also be added to the audio since direct digital transfers from the field recorder to the videotape are not possible since either sample rate conversion or an analog transfer must be used as a result of the speed change.

Most audio engineers therefore prefer to use the original source material when working with film audio. Once the original audio has been digitally transferred into Nuendo, the speed change must be compensated for in order to have the audio stay in sync with the video. Nuendo has the flexibility to apply these speed changes to either the audio or video independently to compensate for the speed change.

When a specific speed change has been applied to either audio or video, it is called a “pull-down” or “pull-up” depending on the direction of speed change. The specific amount and direction of speed change depends on the type of transfer the film underwent. Transfers to PAL/SECAM and NTSC each require a different speed change in order to keep the audio in sync. These speed changes arise during the Telecine process.

The Telecine process

A telecine machine is the device used to transfer film to videotape. It transfers images from each frame of film to frames of video in a very specific way. Having a clear understanding of this process will help alleviate the confusion surrounding pull-up and pull-down sample rates and keeping film audio in sync.

Film frames vs. video fields

One of the first things that needs to be understood is how video signals are formatted in general. Each frame or single image of a video signal is composed of two video “fields”, each containing half of the image. The first field contains all the odd horizontal lines of resolution and the second field contains the even horizontal lines of the image. This is called “interlacing” and is needed to minimize the flicker effect that would result if the image was presented all at once.

Since the film frame is a single, complete image (like a 35mm photograph), there are no fields involved. The telecine machine must transfer part of the film image to one field and then the rest to another field of video. This may sound simple at first but as you will see, it can become quite complex.

Transferring film to PAL/SECAM video

Film transfers to PAL/SECAM video are relatively straightforward. Film runs at 24 fps and PAL video runs at 25 fps. If you speed up film by roughly 4% (or 4.16%, to be precise), it will be running at 25 fps. So, film transfers to PAL video result in a 4% “pull-up” in speed. The audio must also be pulled up by 4% in order to remain in sync with the video.

When properly done, the first frame of film will be transferred to both fields of the first frame of video and so on. All that is needed is the 4% increase in speed for this to be a one-to-one transfer.

The only downside to PAL transfers is that a 4% increase in the speed will result in a 4% increase in the pitch as well! This could affect the perception of a character’s delivery of a line or the timbre of sound effects or musical tonalities. If the final project is to remain in the video format, pitch-correcting this anomaly might be desired.

If the project is going to be returning to film for the final presentation, the audio can be slowed back down to normal speed when transferring back to film in order to preserve the fidelity and performance values of the original material.

Transferring film to PAL/SECAM video requires a 4% pull-up in speed for both the picture and sound elements.

Transferring film to NTSC video

Transferring film at 24 fps to NTSC video at 29.97 fps presents a few more difficulties than the PAL transfer. Simply speeding up film to 29.97 fps would cause both the visual and audio elements to become too fast and high-pitched to be usable. There is no neat mathematical relationship between 24 fps and 29.97 fps. Another method was devised called the 2-3 Pull-down.

What is 2-3 Pull-down?

The 2-3 pull-down is a combination of speed change and frame-to-field-counting that results in a smooth transfer to NTSC video without any unwanted or noticeable pitch changes in the audio. Here are the steps involved during the process:

1.The film speed is slowed or “pulled” down to 23.976 fps (-0.1%).

At this speed there is a mathematical relationship between 23.976 and

2.The first frame of film is transferred to the first two fields of video.

3.The second frame of film is transferred to three fields of video, the two fields of the second video frame and just the first field of the third video frame.

This is where the “2-3” part of the name comes from. Each alternating frame of film is transferred to two fields of video then three fields of video and so on.