3 and 4-Point Loops in Clip Player

A 4-Point Loop describes a clip that has at least a loop part and an intro or an outro or both. To define a 4-Point Loop, the loop in and out time code and the number of times the loop part should be repeated, possibly infinite, are required.

Example: 4-Point Loop Use

4-Point Loops can be useful in a wide variety of cases where you need to loop a video segment. Perhaps you do not know in advance exactly how many times you want to loop the video. For example, let us assume the video clip is a spinning globe animation. You know you have an intro, but how long the globe should spin, is dependent of the time another scene item is shown, say a video of the anchor speaking. When the anchor-video is done, you want the spinning globe to exit the scene.

Parameters for 4-Point Loops in the Stage Editor

Additional fields have been added to the clip setting pane where loop in, loop out and loop count can be set as shown in the image below. No additional command is needed to start or stop the loop.

Click on the Clip channel to view the 4-Point Loop parameters.

During scene-design the values of the 4-Point Loop are recalculated automatically when the Key Frames are changed by dragging them in the director tree. Any changes made in the entry fields are reflected in the time line pane to show the real-time length of the clip. When the start or the end frame of the clip is dragged, it snaps to the nearest possible time code to have an integer loop count.

Play Clips with Resolutions Different from Channel

It is possible to play clips even if the resolution is different from the one set for the channel. However, there are some restrictions to that:

• Can only play clips from the same genlock family.

• The clip’s resolution must be of a regular broadcast format. For detailed information on which combinations are possible check the appendix.

Frame Accurate Clip Playback

If the clip, in the stage, needs to be played frame accurately, these features need to be set to active:

• First, the pending clip playback support has to active. If not, the clips are not ready when needed (see the Video Input: Clip Input page in the Configuring Viz section of the Viz Engine Administrator Guide).

• Additionally the Frame Accurate Viz Commands (FAVC) need to be set to active in Global Properties (see the Communication page in the Configuring Viz section of the Viz Engine Administrator Guide).

• And the Command Execution Field Dominance should be set to Odd Retrace Counter (see Communication > Global Properties in the Configuring Viz section of the Viz Engine Administrator Guide). When using external control applications, it may be necessary to tweak the FAVC Bias.

For a scene containing a clip in the stage to play frame accurately it is necessary to use the SCENE*CUE command, which preloads the first clip Key Frame.

Playing Overlay Clips (Not Full Screen)

Playing a clip which is not full screen in size, like a spinning logo, an insert snipe or a special effect without audio. These are known as overlay clips. To play overlay clips it is recommended to use the VML clip player. VML supports clips with alpha and plays a lot of codecs.

SoftClip is able to play all installed VFW (Video For Windows/AVI) codecs on your computer. Please note that VfW is officially deprecated. There are dozens of codecs available, each with it’s own advantages and drawbacks. There is no general rule which codec to use (see Supported Codecs), but it is recommended to use the different types of Matrox codecs (depending on whether the alpha channel is necessary or not).

Playing UHD Clips

Clips in Ultra HD resolution require a lot of CPU resources for decoding. A strong CPU is required. The performance depends on the used codec, bitrate, color depth etc. It is recommended to use a special decoder board from Matrox (Matrox M264) in combination with a Matrox topology board.

Slow Motion Playback

A shuttle rate between -1.0 and 1.0 results in the clip playing slower than normal, where negative values result in a backwards playback. The actual frame to play is determined by the internal frame counter which is increased on every grabbed frame. For a frame rate of 0.3 this would be:

Fast Forward and Fast Backward

A shuttle rate <-1.0 or >1.0 results in the clip playing faster than normal, where negative values result in a backwards playback. The calculation of the next Frame to be delivered is done the same way as described above using the set shuttle rate.

Flushing Clip Channels

The FLUSH command can be used to clear the active clip player and reset all parameters to their default value. All valid clip frames still in the pipeline are cleared as well and black is sent. If the pending clip player also needs to be cleared, send FLUSH to the PENDING command channel.

Repeat Mode

Determines how clip playback should behave when paused:

• None: Black is played out.

• Frame: The last frame is shown, which shows both fields.

• Field: Only the last field is shown, copied to first and second field. This setting is only relevant if the clip’s scan mode is interlaced.

Reverse Fields

This setting is used for smooth playback when playing interlaced clips in reverse. Enabling reverse fields swaps the playback of first and second field during reverse playback. This setting applies only to interlaced clips.

Loop Mode

If on, the clip loops infinitely between clip in and out times.

Auto Run

If on, the clips start immediately after being loaded and delivering the first frame.

Scripting

The scripting interface refers to the plug-in interface and has therefore the same limitations as the plug-ins have. To use a clip channel in scripting, first retrieve a channel from the system:

This object can now be used to control the clip channel:

The scripting interface to clip channel allows for the same use cases as the plug-in interface does.

Plug-ins

The plug-in interface provides almost all functions available in the Command Interface. The only limitation here is, all functions refer to the current scene. The use cases are the same as described in 3 and 4-Point Loops in Clip Player. Stage use cases cannot be addressed with the plug-in interface.

Source PAL

Source 720p

Source 1080i

See Also

• The Stage for Animation

• Key Frame Editors

• Channel Editor