General procedure

Step A: Design the dynamic playlist

Identify inputs

1. Identify the inputs and the order in which they are to play.

• The first input can be a live asset or a file asset.

• The inputs can be all live assets, all file assets, or a mix of live and file assets.

• The same input can be repeated as many times as you want in the dynamic playlist.

Generally, it is a good idea to add the inputs to the event in the order in which they will be played. You should do this even if you plan to specify a start time for some or all inputs (below).

Identify inputs to prepare manually

2. Identify inputs that must first be prepared:

• Live streaming inputs: You must manually prepare each live input before it is due to be played.

• File inputs: There is no need to manually prepare file inputs, but you may do so if you prefer. Perhaps a reason to prepare is that you know you have to prepare live inputs and you want to follow the same steps for both live and file inputs.

Identify inputs to activate manually

3. Identify inputs that must start at a specific time, rather than simply starting after the previous input ends.

If you follow the recommended procedure (Step E: below), you will need a placeholder input. Read the procedure in Step E: so that you can prepare this input now.

Step B: Create and start the event

4. Create the event with only the first input. (If the event contains more than one input, the others will be deleted when you create the dynamic playlist.)

Use the REST API Create Event command or use the web interface. See below for tips on setting up the event for the different use cases.

5. Start the event. Use the REST API or the web interface. Processing starts on that single input.

Step C: Add more inputs

6. Once the event has been started, you can create the dynamic playlist in order to add more inputs to the event.

There are two ways to add inputs to the dynamic playlist:

• Use the Add Dynamic Playlist Inputs command to create an array of inputs that are appended to the inputs currently in the event. Up to 29 inputs can be added in this way. For more information, see Add dynamic playlist inputs.

• Use the Replace Dynamic List command to create an array of inputs that replaces the existing dynamic playlist (except for the currently running input). You can add any number of inputs this way. For more information, see Replace dynamic playlist.

Step D: Prepare inputs

7. If you have identified inputs that must be manually prepared, then as soon as one of those inputs becomes “next in line”, you prepare it by calling Prepare dynamic playlist input.

• Time the preparation correctly: For a live input, you must prepare enough time in advance to allow Elemental Live to inspect the entire next-in-line input and decode at least one frame. But you should not prepare it too far in advance because once preparation starts, this is what happens:

  Elemental Live inspects the entire input then decodes the first frame in the pipeline. If this input is still not due to run, it discards that frame and decodes the frame that is now first in the pipeline. It discards that frame and decodes the frame that is now first in the pipeline, on and on until the input is due to run. This decoding obviously uses processing resources.

• This timing rule does not apply to file inputs.

• You can optionally specify a prepare time. The input will transition to the Prepare state but no preparing will actually occur until the specified time.

• Keep in mind that you can only manually prepare one input at a time: if you prepare input A, do not prepare the next input until input A is active. If you do, input A may not start as expected.

For more information about the rules around preparation, see Details on preparing inputs.

Step E: Activate inputs

8. For each input that must start at a specific time, set the activate time when the input is next in line.

Activating using placeholders

Scheduling inputs is a bit tricky because an Elemental Live event must always be encoding: there is no concept of waiting for a frame to arrive. Therefore, if you do not time input B to start immediately after input A ends, then Elemental Live will move to the next input that does not have an activate time (perhaps the input that appears after input B in the XML). But it is very difficult to get this timing between inputs exact enough.

The workaround is to use a “placeholder” input between inputs A and B, as follows:

• Estimate the expected end time of input A.

• Assign an activate time for input B that is as close to the end time without being before it. (In this way, input A is not interrupted.)

• Between input A and input B insert a “placeholder” file input (this input could be a blackout slate, for example). Do not assign a start to this placeholder but do set the loop_source tag to true for this input in order to play the content repeatedly until it is time to return to the live input.

This will be the result: if input A end time does not exactly match the activate time for input B, then the placeholder will play. When the activate time for input B arrives, the placeholder will be interrupted by input B. Input B will start at the scheduled time.

Step F: Continue adding to the dynamic playlist

9. As inputs are run, add more inputs to the event.

• So long as the event is still running, you can continue to add inputs to it; the event will not end.

• Add inputs using either the Add Dynamic Playlist Inputs command or the Replace Dynamic List command.

Step G: Interrupt the currently active input

Occasionally, you may need to interrupt the current active input and start a different input (input B). See Implementing use case 3 for an example of an unanticipated interruption.

• If necessary, add input B to the dynamic playlist. There are two ways to add:

  • Rebuild the entire playlist, with input B inserted at the top, using the Replace Dynamic Playlist command. The currently active input will not be removed when you do this. For more information, see Replace dynamic playlist.

  • Append input B to the end of the playlist, using the Add Dynamic Playlist Inputs command. The drawback to this method is that the input appears at the end of the playlist on the web interface, but then gets activated, which may confuse your operators. For more information, see Add dynamic playlist inputs.

• If input B is a live input, prepare it using the Prepare Dynamic Playlist command. For more information, see Prepare dynamic playlist input.

• Use the Activate Dynamic List Input command (without an activate time) to immediately activate the input. For more information, see Activate dynamic playlist input.

Step H: Clean up the playlist

10. The dynamic playlist is never automatically cleaned up; even after an input has been processed, it remains on the dynamic playlist.

• If you use the Replace Dynamic Playlist command, the entire playlist is replaced, which effectively cleans up old inputs. Fore more information, see Replace dynamic playlist.

• If you use the Add Dynamic Playlist Inputs command, then you may want to occasionally use the Delete Dynamic Playlist Input command. For more information, see Delete dynamic playlist input.

Step I: Troubleshoot

If the dynamic playlist is not behaving as expected, see the information about preparation and activation, starting here. You may have broken a preparation or activation rule.