Timeline displays a representation of the open FLV file and provides means to navigate the preview video. Also entering the time codes is easier with the timeline.
FLV format consists of video/audio/data tags with timestamps. Although video tags usually occur at regular time intervals, there are no actual frames (in the sense that FLV is a wrapper format).
You can select any time value (in millisecond precision) to insert the markers/captions, by clicking on the timeline. Playhead time is used as the time with many commands such as 'Add a Blank Marker', 'Add a Blank Caption' and 'Add New Cue Point'.
Note that if the Video Preview Window is open, the times that can be seeked will depend on the time codes of the key frames in the preview video. Furthermore, for a FLV file preview, the time values will correspond to timestamps in the FLV. (For example, if you open a data-only FLV and play it, you'll get time values only for the tags present in the file).
Playhead Time
Shows the current playhead time in hours:minutes:seconds:milliseconds format.
Markers/Cue Points
Shows the markers listed in the Markers Tab or cue points listed in the Cue Points Tab.
V/A/D or A + V keyframes
Shows the Video/Audio/Data tags in the FLV. Video key frames will have a brighter green color than the intra frames. Audio tags are medium purple. Data tags (orange) will usually not be present, since the tags shown here exclude the tags that will be injected by Captionate.
A + V keyframes
If the audio codec used in the open FLV is MP3, by decoding the MP3 file of the audio to a WAV file, Captionate can display a graph of the audio data (approximate sound amplitude/volume) and video key frames (as green background rectangles) on the timeline, with View | Preview Audio Graph on Timeline command.

Processing may take some time, depending on the size of the FLV file. Unfortunately, currently, the data calculated is not cached. (The file will be processed every time you 'check' the menu command).

This option, when available, is most helpful with sound tracks that doesn't have any background music etc., still it will help, especially if you set the zoom level correctly (For precision work, you'll need to set the zoom level to 1,5 or 10 ms/px).
tip You can use F3 to move the selected marker/caption/cue point to the current playhead time on the timeline.
tip Use 'Audio Only' (use the audio of the current FLV file) video preview to be able to select any time on the timeline while the preview is open.
(This feature does not take 'the audio delay' latency into account. Also it assumes the audio tags start at the beginning of the FLV and continues uninterrupted. You can make sure the graph is correct by playing video preview and watching if it synchs with the graph before depending on it).
Shows the captions for the selected language track listed in the Captions Tab.
Cursor time
At the left bottom corner, the time value that the mouse cursor is over, is shown.
Mode Buttons
: Normal mode. In this mode, you can click on the timeline to seek the time. You can also drag the playhead with mouse.
: Selection zoom in mode. In this mode, you can select an area on the timeline with mouse to zoom into. Still, clicking on the timeline will function as zoom in, and clicking with CTRL button down will function as zoom out.

Zoom Buttons
: Zoom in: Magnifies the view by a factor of 2x.
: Zoom out: Reduces the magnification by a factor of 2x.
: Zoom menu: Lets you select the zoom level. The ms/px unit means how many milliseconds will be represented by each pixel. For example 25ms/px means 25 milliseconds is represented by 1 pixel, therefore a second will be 40 pixels wide. Current zoom level is shown next to this button.
Show All zoom value depends on the current width of the timeline.

Above: At 1ms/px zoom, every pixel corresponds to 1 ms. A marker and a caption can be seen above. The first video tag is a key frame. All tags are displayed in alternating colors.
Controller Buttons
: Go back 10 seconds (F5)
: Step back 0.5 seconds (F6)
: Step forward 0.5 seconds (F7)
: Go forward 10 seconds (F8)
/: Play/Pause (F9)
: Stop (ALT+F9)