Configuring the start time for the output timecode

You can configure the start time for the output timecode that MediaLive includes in output encodes.

Note

This procedure assumes that you are familiar with creating or editing a channel, as described in Creating a channel from scratch.

1. On the Create Channel page, in the General settings section, choose Timecode configuration.

2. In Source, choose the option for initializing the timecode in the output:

   • EMBEDDED – Use the timecode embedded in the source video.

     MediaLive looks for the timecode in the source video, as follows:

     • H.264 – A timecode inserted in an SEI message of type pic_timing, in accordance with section D.1.2 of ISO/IEC 14496-10-2005

     • H.265 – A timecode inserted in an SEI message of type timecode, in accordance with section D.2.26 of ITU-T H.265

     • MPEG2 – A timecode inserted in each GOP header, in accordance with section 6.2.2.6 of ISO/IEC 13818-2-2000 (R2006)

   • SYSTEMCLOCK– Use the UTC time.

   • ZEROBASED – Use 00:00:00:00.

3. (Optional) In Sync threshold, enter a threshold (in frames) for synchronizing the output timecode to the input timecode. For information about this field, see About the synchronization threshold.

How the output timecode works at runtime

Initial channel start or restart

When you start the channel, the channel establishes the start timecode for the output pipeline:

• The channel samples the input timecode, if you set up the start time to reference the embedded timecode. If MediaLive doesn't find an embedded timecode in the source, it falls back to UTC.

• Or it sets the timecode to the current UTC time.

• Or it sets the timecode to 00:00:00:00.

The channel generates a new timecode for each output frame that it produces.

Input switches

When the channel switches to a different input, MediaLive doesn't reinitialize the timecode. Therefore, the output timecode isn't disrupted by an input switch.

Pausing and unpausing

If you pause the channel, MediaLive continues to encode frames, which it immediately discards. But because MediaLive continues to encode, the timecodes continue to increment. Therefore, when you unpause, there will be a timecode discontinuity in the output.

About the synchronization threshold

The timecode Sync threshold field synchronizes the output timecode with the input timecode. Drift can occur in several ways. For example, processing issues can occur that cause MediaLive to drop or repeat frames to compensate. Or there might be discontinuities in the input timecode stream.

Purpose of synchronization

Synchronization is useful if it is important for your workflow that the output timecode (that MediaLive generates) match the original input timecode.

• Matching might be important if you know that the downstream system must identify specific frames.

  Typically, the downstream system has already identified these frames based on the original input timecode. Therefore, the output timecode must match the original input timecode, in order for the downstream system to find the desired frame.

• Matching isn't important if the main purpose of the output timecode is simply to uniquely identify each output frame.

How synchronization works

After the input timecode and the output timecode have drifted apart by the specified number of frames, MediaLive inserts a discontinuity in the output timecode sequence, and sets the output timecode to match the current input timecode.

The main drawbacks of synchronizing are that it introduces timecode discontinuities into the metadata, and that it can't guarantee that each output timecode is unique.