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.

The 4-Point Loop features are only supported on video version of Viz Artist and require Matrox hardware to work (i.e. X.mio, X.open or DSX LE).

Example: 4-Point Loop Use

4-Point Loops can 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 (2) 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 Viz Configuration)
  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 SoftClip clip player. Even though SoftClip can play clips up to HD 1080, it should be mainly used for overlay clip playback. For full screen playback there is a more efficient clip player available in Viz. The advantage of the SoftClip clip player is that it can play clips in any pixel size, aspect ratio or frame rate. SoftClip is based on the VFW (Video for Windows) AVI clip playback workflow on Windows.

SoftClip is able to play all installed VFW (Video For Windows/AVI) codecs on your computer. 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), avi uncompressed or the freely available HuffYuv codec. SoftClip supports RGBA playback if the codec is able to store the alpha channel; avi uncompressed supports alpha, also the Matrox Mpg2iFrame&alpha codec and the HuffYuv codec, just to mention a few.

A typical use case for the SoftClip player would be:

• The playback of a spinning looping logo with alpha channel. The size of this clip could be around 350x350 pixels

• The playback of an explosion overlay clip with alpha. The size is around 500x500 pixels

• The playback of a snipe/insert with alpha. The size is around 600x150 pixels

  Note: The SoftClip player is not intended for full screen playback.

Clip with Audio (Not Full Screen)

Playing a clip with audio which is not full screen in size, like a strap of an advertiser, a 3D object transition or an effect or a reveal of an item only.

To play clips which need audio, but do not need to be played back in full screen mode, use MoViz. MoViz is very similar to SoftClip, with the main difference being that it supports audio. MoViz is based on the DirectX clip playback workflow on Windows, which means it uses a different library and codec filters than the SoftClip plug-in.

If you install a VFW codec for avi playback like for SoftClip, it is not guaranteed that your clip also plays in MoViz, since MoViz is DirectX-based. In general it is very helpful to install the free package of the main concept codecs, since with this package you get dozens of ffdshow filters for DirectX for free and this raises the compatibility with which you are able to play regular avi files via MoViz.

To use the full potential of MoViz you should encode clips with ffd instead of avi. If you want to render clips into ffd, as an example from Adobe After Effects, there is a new section showing up in the render section named ffd, besides QuickTime and Video for Windows, TGA single frames and others. In the ffd settings you can select the necessary format, like dv, mpg and many others.

A typical use case for the MoViz player would be:

• The playback of a insert advertiser with audio on the bottom of your screen. The size of this clip would be something around 720x150 pixels.

• The playback of a ’clip universe’: the animated Viz camera is flying through space and passes clips.

  Note: The MoViz player is not intended for full screen playback!

Clip with Audio (Full Screen)

Playing a clip with audio in full screen mode, but only using it as a background in my Viz scene. The clip does not need to be rotated in 3D space.

To play full screen background clips it is recommended to use the Matrox clip channels. The dimensions and frame rate of these clips must be either HD 1080, HD 720, PAL or NTSC. Any free pixel size, aspect ratio or frame rate is not supported on the Matrox channels.

If the clip is 2D, meaning there is no transformation/rotation in 3D space needed, then you should set the Matrox clip channel to DVE. In DVE mode you get the maximal clip quality achievable.

When using DVE mode, do not forget to apply a key function to your Viz items or switch the renderer to autokey, otherwise they do not show in front of the clip (see Keying Mode).

If you want to use an alpha channel on this clip, use the Matrox Mpg2iFrame&alpha codec and configure the clip channels in Viz Configuration (see the Viz Engine Administrator Guide) correctly (activate alpha). Also here it is recommended that you use the Matrox AVI codecs, but the Clip channels support many more formats than just the Matrox codecs (see Supported Codecs).

A typical use case for the DVE setting would be playback of a clip at it’s best quality, with or without any overlaying graphics.

Clip with Audio (Full Screen and 3D Space Transformation)

Playing a clip with audio in full screen mode and transforming it in 3D space. To play full screen clips it is recommended that you use the Matrox clip channels. The dimensions and frame rate of these clips must be either HD 1080, HD 720, PAL or NTSC. Any free pixel size, aspect ratio or frame rate is not supported on the Matrox channels. To be able to transform the clip in 3D space you must set the clip channel to Texture. Compared to DVE mode, the clip is slightly more blurred, but this is essential to avoid noise on the clip texture when moved or rotated in 3D space.

If you want to use an alpha channel on this clip, use the Matrox Mpg2iFrame&alpha codec and configure your clip channels in Viz Configuration (see the Viz Engine Administrator Guide) correctly (activate alpha). Also here it is recommended that you use the Matrox AVI codecs, but the Clip channels support many more formats than just the Matrox codecs (see Supported Codecs).

A typical use case for the Texture setting would be:

• The playback of a clip in 3D space with transformations on rotation, scaling and position.

• The playback of a clip on a 3D object.

  Note: Using the Matrox clip channels for playback is the most efficient clip playback for full screen clips.

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 Video Clip Playback Considerations. 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