Adding Transcoded Channels

Transcoded channels transcode a single source into multiple bitrates for output to an HTTP or S3 target.

Supported Video and Audio formats include:

• Video Decoding – MPEG2, H.264/AVC , H.265/HEVC
• Video Encoding – MPEG2, H.264/AVC , H.265/HEVC

• Audio Decoding – AAC, MPEG-1 Audio Layer I / II / III, MPEG-2 Audio Layer I / II / III, AC-3 (Dolby Digital)

  For AC-3, which can contain up to six discrete channels of sound, the transcoder only supports the left and right channels and will ignore the other channels.

• Audio Encoding – AAC, AAC-HE (High Efficiency) and AAC-HEv2; Pass through (no encoding) – any audio codec (MPEG1/2 / AAC / AC-3, E-AC-3 (Dolby Digital Plus). 

  AAC-HE and AAC-HEv2 are only supported for Zixi Broadcasters, v13 and up.

The following procedure describes how to add a Transcoded Channel in ZEN Master. In addition, an explanation of each of the configuration parameters is given in the table below.

To add a Transcoded Channel:

1. In the main navigation, click Channels.
2. Click + Add.
   The Create New Channel selection menu is displayed.
   
3. Click on Transcoded.
   The Create Transcoded Channel window is displayed.
   
4. In the Info section, in the Name field, enter a logical name for the Channel.
5. In the Tags field, select one or more of the predefined Tags from the drop-down list.
   Tags are used for access control. By selecting an Tag, you are relating this Channel to that Tag. Tags are associated with certain roles (through the Users & Roles screen), and roles, in turn, are associated with users and user groups. If you would like to create a new Tag, see Creating a Tag.

6. In the Events Configuration Profile field, select from the dropdown list the profile that you would like to apply to this Channel. By default, the Default profile is applied.

   Events Profiles consist of a series of rules that determine precisely how various types of Events are logged and what results they trigger.

7. In the Configuration section, in the Processing Cluster field, select from the drop-down list one of the Channel Processing clusters that has been configured in ZEN Master. The selected cluster will be used to process this Channel.

   For heavy transcoding processes, use a Processing Cluster with a GPU. ZEN Master supports use of AWS, GCP and Azure instances that include Nvidia GPU.

   If the Source does not exist in the cluster, then the cluster will pull the Source automatically.

   If you are assigning the Transcoded Channel to a specific Broadcaster, make sure that the Broadcaster has sufficient available resources (CPU, GPU etc.) to handle the additional load.

8. In the Target Broadcaster/s field, select your broadcaster preference. Either select a specific broadcaster to be used OR specify your preference for using primary vs. backup broadcasters. Options are: Prefer Primary Broadcasters, Primary Broadcasters only, Backup Broadcasters only or Prefer Backup Broadcasters.

   For managed clusters, it is not recommended to select a specific broadcaster, as the broadcaster's availability may not remain stable.

9. In the Source field, select from the drop-down list the desired Source.
10. If you want to configure an alternative path for disaster recovery, in the Alternative Channel (Disaster Recovery) field, select the Channel that will be used as the alternative path. For more details, see Disaster Recovery (Alternative Path). 
11. In the Slate Source field, select a source (typically a File source), which will be streamed as a technical fallback slate. This option is available when transcoding to a multi-bitrate ladder and not passing through the original source.  
12. If you would like to pass the original Source through, then do the following:
    1. Select the Include Source checkbox.
    2. Enter the desired Bitrate for this Source.
13. If you would like to log the HLS Ad Markers for this Channel, select the Log HLS Ad Markers checkbox.
14. If you would like to preserve closed captions for this Channel, verify that the Preserve closed captions checkbox is selected (default).
15. If you would like to crop the input stream, select the Crop checkbox and set the cropping parameters as follows:
    
    1. In the Units section, select the type of units used to define the crop. Options are: Pixels or Percentages.
    2. Enter the crop position for each of the parameters Left, Top, Width and Height in the appropriate fields.
16. In the Renditions section add one or more Transcoding Profiles to the Channel and configure the bitrate for each profile. This is done as follows:
    1. Find the Transcoding Profile that you would like to add either by scrolling through the list of available profiles or by entering a search word into the Filter text-box. If the Transcoding Profile that you would like to add is not yet configured in ZEN Master see Adding Transcoding Profiles.
    2. Add a Transcoding Profile by clicking the  button next to the profile.

    3. Click on the Bitrate textbox for the profile and enter the expected bitrate. Default: the estimated bitrate based on the transcoding profile.

       The value should be the sum of the video and audio bitrates plus a small amount to account for streaming overhead. By default, a value is assigned based on the transcoding profile. For Sources in which either the video, audio or both are not transcoded, the user must manually input the value based on the actual bitrates of the Source. It is important to enter an accurate value since it will be included in the HLS/DASH manifest.

    4. If you would like to assign the transcoding process to a multi GPU broadcaster, select the Multi GPU checkbox, and then select from the drop-down list the desired GPU instance. Options are: 0 (default), 1, 2 and 3.

       This feature is useful if you are running several heavy transcoding activities, as it enables you to distribute the load among several different GPUs.

    5. Repeat the above procedure for each Transcoding Profile that you would like to add to the Channel.

       If you would like to remove a Transcoding Profile from the Channel, click on the  button next to the Source.

17. Select the Ignore Transcode Thresholds checkbox if you would like to override the Transcode thresholds on your Ingest Cluster (i.e. to allow use of full CPU/GPU and memory capacity).
18. In the Initial State section, select the Disabled checkbox if you would like to disable this Channel upon initial configuration.

19. Select the Muted checkbox if you would like to disable error/recovery notifications for this Channel upon initial configuration.

    You can Enable/Unmute the Channel at any time.

20. If you would like to customize the HLS/CMAF (DASH + fMP4 HLS) configuration, click Advanced (for Broadcasters running v12+).
    The Advanced settings are displayed.
    
    
    1. In the External ID field, enter ID that is used when integrating ZEN Master with an external ESNI/ESAM server. For more detail, contact your Zixi representative.
    2. Under HLS, set the values for the Segments and Segment Duration, or if you would like to disable HLS, deselect the checkbox.
    3. If you would like to enable CMAF (DASH + fMP4 HLS), select the checkbox and set the values for the Segments and Segment Duration.
    4. If you would like to convert the captions format from CEA-708 to WebVTT, then select the Convert CEA-708 to WebVTT checkbox.
    5. Under Convert SCTE-35 to EXT-X-CUE-OUT/IN ad markers, select your preference for converting SCTE cues. Options are: None, CUE-OUT only or CUE-OUT and CUE-IN (default).
    6. Under Timecode (EXT-X-PROGRAM-DATE-TIME) Source, select your preference for inserting a timecode. Options are: None, System time (default) or SEI Timecode.
    7. Select the Disable Renditions Synchronization checkbox if you would like to disable synchronization between the Sources. (Supported for Broadcasters v14.8+)
    8. Select the Drop Unaligned Segments checkbox, if you want to drop segments of a multi-bitrate adaptive group that are not aligned. These segments will not be included in the playlist. 
    9. Select Force I-Frames on SCTE-35 markers if a SCTE35 marker is detected and it contains a specific video timestamp (PTS), the encoder will generate an IDR-frame on the video frame with the closest or equal timestamp. If there is no timestamp in the SCTE35 marker, the transcoder will generate an IDR frame as soon as it can.
    10. Select Support MultiAudio to enable multiple separate audio channels if the input stream includes multiple audio channels.
    11. In the Encoder field, if you would like to specify a specific encoder to use for transcoding (decode and reencode processes), select the desired option from the drop down menu. By default, if there is an Nvidia GPU available, it would auto detect and use that, however you can override this behavior by selecting a different option from the list. 
21. Click Save.

Transcoded Channel Configuration Parameters Table