FPS
Frames Per Second sets the rate for animation playback when Real Time playback is enabled. You generally want to set the FPS for your animation only once, and do so before you begin animating anything at all. This is because when you change the FPS, the time of the last keyframe will not match the new animation length. If you want to modify your animation timing, you must do so explicitly.
The FPS rate for NTSC video is 30, for PAL video, it is 25, and for Film, it is 24.
Production Tip: If you made a mistake, you can use a Field cop with a Pushup / Pulldown operation to fix a sequence of rendered-out images and convert them to a different FPS after the fact.
Start / End
The Start field displays the starting frame number of the animation sequence. By default, it contains a value of one.
The End field displays the final frame number of the animation sequence.
Snap Keys
Snaps all keys to integer frame boundaries. This does the equivalent
of chround -a.
Restrict playback range to Start and End frames
If this option in turned on, you will only be able to set time frames within the start and end range. For example, if the range is 1-240 and you try to set the playbar to -43, it will fail. Turning this checkbox off allows you to set the time frame to any value.
Show Range Slider
If this option is turned on, the slider widget underneath the playbar for visually manipulating the playback range is displayed.
Show Audio
Overlays the current audio track on the playbar so you can see audio wave.
Show Ticks
If this option is turned on, the playbar will show ticks representing the frame numbers.
Show Keys
Audio Wave Scale
Allows adjustment of the audio height, when shown on the playbar.
Integer Frame Values
Houdini works with floating-point frame values ( $FF ). When
enableref_win_globanimoptsd, this option confines the display of
frame values to integers ( $F ). When disabled, Houdini allows you
to set the current time to any value, even a fractional time that
does not lie exactly on an exact frame number.
Step
The size of a single increment in frame values. For example, entering a value of 2 here plays every second frame.
Realtime Playback
Enables realtime playback on the playbar. To control the behavior of the realtime toggle, there are two options.
Maintain realtime playback, possibly skipping frames
This option is not recommended for playback of particle simulations, which will still have to compute any skipped frames.
Play every frame, but never faster than FPS
This option is better suited for playback of particle simulations.