Multi-Camera / Mixer

Use the Mixer Viewer to see multiple media playing simultaneously in re-sizable mini-viewers. This can be used in various ways and is useful to edit videos shot by multiple cameras from different viewpoints that were simultaneously recorded in order to create a single good video. Everything will have to be initially synced so you can decide which one of the camera angles is best suited at any time. Mixer mode does not support audio only tracks but there is a workaround described at FAQ, Known Problems and Workarounds.

The number of cameras/mixers you can have is generally limited to the available resources on your computer. Currently, the number of File Descriptors available in the OS limits cameras to about 50. If you have many mixer viewers you will probably want to use proxy mode whenever possible. Also, in the Settings Playback A tab Video Out section, uncheck play every frame and choosing a Video Driver of X11 with use direct X11 render if possible checked, will provide better performance.

Figure 6.8 shows 9 media sources in the left corner, the composed video in the right corner, the timeline with the top video track with pieces of the 9 overwrites, and the choice in Resources of Mixed.

Figure 6.8: Using Mixer capability in Cin for multiple cameras
Image multicam01

Easiest Method to Getting Started

  1. This method assumes all of your media or cameras are aligned the way you want them already.
  2. From the File pulldown, create a New project with the desired format for Audio and Video output (or you can just use the default).
  3. File Load the media files you want to work with using Create new resources only.
  4. In the Resources window, with the Media folder, highlight the list of media you want to Mix. This is done using a ctrl or shift mouse button press as you would in a standard listbox selection.
  5. Right click the mouse on the media selection and choose open mixers . This opens multiple mixer viewer windows, one for each media item that was highlighted. You can do them 1 at a time instead. This also adds the source media tracks to the main window.
  6. Now use the timeline to play and you will see all viewers/cameras playing. Stop when you get to the end of the good camera playback.
  7. Simply double click the good mixer viewer and from where you first started playing to the playback insertion pointer is the source section, which will be pasted in the destination video/audio tracks at the top of the new project.
  8. Repeat steps 6-7. Start playing again, stop when you want, double click the desired mini-viewer!

Some Hints and Caveats

But, I want to use only the first set of audio tracks...

There are many cases where you may want to compose using media from several different tracks while using the the same audio tracks as associated from a specific viewer. Since mixer source tracks can be updated any time by using a mixer toggle, this makes it possible to do this.

Procedure to update the mixer audio source track list:

  1. Single click to highlight the mixer window you want to re-associate to the audio track.
  2. In that audio track’s patchbay click the expand toggle, the arrow on the right side.
  3. In the expanded pane that appears, there is another arrow on the left side. This icon has the tooltip Mixer. Click this and because in step #1 you highlighted the mixer window, it will now be toggled on. Once you click the mixer icon it will then point up.
  4. Now, disassociate any audio that is unwanted by expanding its patchbay and toggling off the mixer.

Expert Usage

When you double click a mixer viewer window, it operates an overwrite paste operation. This moves src (source) track edits to dst (destination) track edits over the same selected timeline region.

Each mixer viewer maintains a list of the tracks which will be used as src. This list is made visible selecting the window with the left mouse button. When the mixer viewer is selected, a highlight is drawn around the media image. All track patchbay mixer toggles are updated to reflect the src tracks included in the selected viewer src track list. The play track patchbay toggles can be used to manage the list.

New Mixer viewers can be created using the main menu Window Mixer Viewer, or with a shortcut of Shift-M. When a new viewer is created, the currently enabled patchbay mixer toggles are used to create the viewer source track list. The toggles are cleared after the window is created. This is to improve the work flow. Use the following list of steps to create individual mixer viewers.

To create a list of mixer viewers:

  1. Setup the session settings format, width, height, frame rate, color model, aspect ratio.
  2. Create dst tracks using the a/v track pulldowns (or use shortcuts "t" / "T"), armed and playable.
  3. Append src tracks using file open append tracks, or the resource window using pasting.
  4. Using the track patchbay, disarm editing and disable playback of the audio/video src tracks.
  5. Using the track patchbay, mark the new tracks as mixer source to be added to the viewer.
  6. Create a mixer viewer using the main menu pulldown, or the shift "M” shortcut.
  7. Repeat steps 3 - 6 for each mixer viewer needed for the session editing.

When you single click a mixer window, it becomes selected and highlighted and all of the patchbay mixer toggles are updated to reflect the state of the viewer’s src tracks. Tracks that will be src are shown as enabled. If you change a toggle, the src tracks for the selected window will be modified. This means you can associate or dis-associate any media track to any mixer window.

When you double click a mixer window, an overwrite paste is invoked. The mixer viewer’s src tracks are overwritten to the dst tracks. The timeline region for both the source and destination are the same for the overwrite paste function. The selection region is used if it is active. If the selection is empty, that is it is a hairline, the selection region is from the end of the destination playable edits to the selection cursor hairline. The hairline must be past the end of the playable edits on the destination tracks.

The mixer viewer configuration is saved with the session data. When a saved session is loaded in replace project or replace project and concatenate tracks, the mixer viewer will be reopened.

Using Proxy with Open Mixers

The best way to use proxy with your multiple cameras is to follow the steps below:

  1. Load media with insertion strategy of create resources only.
  2. Highlight the media in the Resources window and right click on this to choose open mixers.
  3. Use the Settings Proxy bring up the proxy menu.
  4. Choose the size and other options you want and click the checkmark OK. If you choose the option Beep when done you will hear a short beep if all media is already proxied or a longer beep when all proxies have been created.
  5. When your editing is complete, use Settings pulldown and proxy to original size.
Instead of Open Mixers, you can Insert Mixers with new tracks at the timeline insertion point.

Options available in the Mixer Windows

There are several options you will see in each Mixer viewer that help with using them. These are shown in figure 6.9. To use these, RMB in the desired mixer window, and choose one of the options as described here.

Figure 6.9: A Mixer window showing available options with the white X designating no playing
Image mixer-playable

  1. Fullscreen / Windowed - will bring up a fullscreen display of that window or revert to the original size.
  2. Resize Window - allows for resizing the window to a choice of different sizes.
  3. Tile Mixers - makes it easy to get all of the mixers nicely tiled to a standard size. This is also available in the Window pulldown.
  4. Playable - enabled by default so that you will see a checkmark next to it in the popup. The benefit of making a mixer window not playable is to save cpu time. When a specific mixer window is unchecked, so not Playable, a white cross appears in the upper left hand corner of the mixer. To switch back to playing again, RMB and choose Playable and this will turn playing back on. The program automatically updates the mixer image when the timeline cursor stops or when it is moved to a different spot even when play is disabled. You can see the white cross designating not playable in figure 6.9. Statistics that show the savings are as follows on a 16 cpu laptop:
    	5 Mixers all playing -- cpu usage = 1275
    	1 only playing       -- cpu usage =  405
    	2 only playing       -- cpu usage =  800

Mixers pulldown

From Program windows menu we can access the windows mixers... there are several entries available (see figure 6.10):

Figure 6.10: Mixers... pulldown
Image mixers-pulldown

Mixer Viewer:
(Shift-M) opens a new empty Mixer 1 window, which will then be associated with a track. We can open as many Mixers as we like.
Drag Tile mixers:
(Alt-t) the default size of a mixer window is related to the std size of the Viewer window. If we want to modify it at our convenience, we can build a window of the desired size with the Drag Tile mixers function and then automatically order our mixers within it with the right click of the mouse.
Align mixers:
see Audio/Video sync via Waveform
Mix masters:
this feature makes it very easy to get into the multi-camera mixer mode after tracks have already been set up and edited. Before this addition, you could only Open Mixers from original media assets in the Resources window.
If the mixers of several sources have been opened, the entries of each assets will appear, useful for recalling a specific mixer window.

The CINELERRA-GG Community, 2021