Ad markers

This guide describes the ad markers supported by the Video Stitcher API. The Video Stitcher API identifies ad break boundaries by ad markers in a live stream's source HLS/DASH manifest and performs ad stitching within an ad break for every session of the live stream.

Before you begin

Make sure you are familiar with the introductory concepts and terminology in the Video Stitcher API. For more information, see the technical Overview.

See SCTE-35 specification Digital Program Insertion Cueing Message For Cable.

SCTE-35 commands

Live stream ad markers are represented by standard SCTE-35 signals. Within the list of SCTE-35 commands, the Video Stitcher API supports the following two commands:

  • splice_insert
  • time_signal

With time_signal, you can provide additional arbitrary metadata for the associated ad break in the UPID payload. The Video Stitcher API expects the UPID payload to be a JSON string, in which certain JSON keys are reserved for the following specific purposes:

  • %%AD_TAG_ID%%: Specifies the ad tag to use for the ad break. The ad tag ID should be one of the keys in the live session's adTagMacros.
  • %%SLATE_ID%%: Specifies the slate to use for the ad break. The slate ID must match the ID for a slate that has already been created in the same Google Cloud project.

All other key value pairs in the UPID payload are used for ad tag macro replacement.

HLS ad markers

EXT-X-DATERANGE

Using #EXT-X-DATERANGE is specified in the HTTP Live Streaming specification:

  • An #EXT-X-DATERANGE tag with attribute SCTE35-OUT indicates the immediate start splice point of an ad break.
  • An #EXT-X-DATERANGE tag with attribute SCTE35-IN indicates the immediate end splice point of an ad break.
  • The values for SCTE35-OUT and SCTE35-IN are expected to be hex-encoded.

Example:

#EXT-X-DATERANGE:ID="111",START-DATE=START_DATE,SCTE35-OUT=0xFC302000000000000000FFF00F050000006F7FFF7E002932E0000000000000235EE5EF
...
#EXT-X-DATERANGE:ID="111",START-DATE=START_DATE,END-DATE=END_DATE,SCTE35-IN=0xFC302000000000000000FFF00F050000006F7F7F7E002932E0000000000000D56C4036

EXT-X-CUE-OUT and EXT-X-CUE-IN

An #EXT-X-CUE-OUT tag indicates the immediate start of an ad break, and an #EXT-X-CUE-IN tag indicates the immediate end of an ad break.

An #EXT-OATCLS-SCTE35 tag can be used for SCTE-35 message, and the value is expected to be base64-encoded.

Example (without SCTE-35 message):

#EXT-X-CUE-OUT:DURATION=30
...
#EXT-X-CUE-IN

Example (with SCTE-35 message):

#EXT-OATCLS-SCTE35:/DBBAAAAAAAAAP/wBQb+AAaXgAArAilDVUVJAAAAb3//AAApMuAMFXslJUFEX1RBR19JRCUlOnRhZy0xfTQAALOJefk=
#EXT-X-CUE-OUT:30
...
#EXT-X-CUE-IN

If the duration of an EXT-X-CUE-OUT tag is specified, then that value takes precedence even if the ad break duration in the SCTE-35 message conflicts with it. If the duration of the EXT-X-CUE-OUT tag is not specified and one is specified in the associated SCTE-35 message, then the value from the SCTE-35 message is used.

DASH ad markers

Currently, the Video Stitcher API only supports multi-period DASH manifests. In a multi-period DASH manifest, an ad break should be represented by a Period with an event stream containing a cue-out marker. A cue-in marker is not required as the end of the ad break period indicates the end of the ad break.

If multiple cue-out events are presented in an ad break period's SCTE-35 event stream, the Video Stitcher API will only use the first one. The presentation time of the cue-out event is ignored as the break start time is the same as the period's start time.

The following is a list of supported schemeIdUri for an SCTE-35 event stream:

  • urn:scte:scte35:2014:xml+bin
  • urn:scte:scte35:2013:xml

urn:scte:scte35:2014:xml+bin

An event stream whose schemeIdUri is set to urn:scte:scte35:2014:xml+bin contains events representing SCTE-35 messages in base64-encoded binary.

Example:

  <Period start="PT444334H55M0.010S" id="break-1">
    <EventStream schemeIdUri="urn:scte:scte35:2014:xml+bin" timescale="90000">
      <Event presentationTime="0" duration="5400000" id="1">
        <Signal xmlns="urn:scte:scte35:2014:xml+bin">
          <Binary xmlns="urn:scte:scte35:2014:xml+bin">/DBTAAAAAAAAAP/wBQb+AAaXgAA9AjtDVUVJAAAAAH//AABSZcAMJ3siJSVBRF9UQUdfSUQlJSI6InRhZy0xIiwiZGFzaCI6InRydWUifTQAABxkspA=</Binary>
        </Signal>
      </Event>
    </EventStream>
    ...
  </Period>

urn:scte:scte35:2013:xml

An event stream whose schemeIdUri is set to urn:scte:scte35:2013:xml contains events representing SCTE-35 messages in clear XML.

Example:

  <Period start="PT444334H55M0.010S" id="break-1">
    <EventStream timescale="90000" schemeIdUri="urn:scte:scte35:2013:xml">
      <Event duration="5400000">
        <scte35:SpliceInfoSection protocolVersion="0" ptsAdjustment="140429" tier="4095">
          <scte35:SpliceInsert spliceEventId="1" spliceEventCancelIndicator="false" outOfNetworkIndicator="true" spliceImmediateFlag="false" uniqueProgramId="1" availNum="1" availsExpected="1">
            <scte35:Program><scte35:SpliceTime ptsTime="5672624400"/></scte35:Program>
            <scte35:BreakDuration autoReturn="true" duration="5400000"/>
          </scte35:SpliceInsert>
        </scte35:SpliceInfoSection>
      </Event>
    </EventStream>
    ...
  </Period>

Early ad break notification for live streams

For live stitching, ad tags are processed synchronously when the Video Stitcher API receives the cue-out ad marker in a live stream's manifest. This synchronous processing triggers a large number of ad tag requests and causes long delays for the live session's playback requests if the stream is highly populated.

Early ad break notification (EABN) gives the Video Stitcher API more time to prepare ads by notifying the API of an upcoming ad break.

HLS early ad break notification

To notify the API of an upcoming ad break so the API can prepare ads in advance, a live stream's HLS playlist must:

  • Use #EXT-X-DATERANGE or EXT-X-CUE-OUT as the ad marker
  • Repeat a cue-out ad marker in the live stream's source manifest

#EXT-X-DATERANGE

When the source encoder schedules an upcoming ad break, it can insert an #EXT-X-DATERANGE cue-out marker into the source manifest. The marker's X-TYPE attribute indicates the type of ad marker; for early ad break notification, the value for X-TYPE is expected to be EABN. The marker's START-TIME attribute indicates the actual or planned ad break start time. The marker's DURATION attribute is required to indicate the duration of the ad break. This marker is called an EABN cue-out.

At the actual start of the ad break, the source encoder must insert an #EXT-X-DATERANGE cue-out marker into the source manifest. The marker's ID attribute must be the same as the corresponding EABN cue-out. The marker's START-TIME must be the same as the segment's media time at which this marker is inserted. This marker is called an immediate cue-out.

The following sample manifest contains one EABN cue-out, one immediate cue-out, and one cue-in:

#EXTM3U
#EXT-X-TARGETDURATION:4
#EXT-X-VERSION:7
#EXT-X-PROGRAM-DATE-TIME:2020-11-08T21:11:20.976Z
#EXT-X-MEDIA-SEQUENCE:239959
#EXT-X-DISCONTINUITY-SEQUENCE:2
#EXT-X-DATERANGE:ID="2415919105",X-TYPE="EABN",START-DATE="2020-11-08T21:11:28.976Z",DURATION=29.988,SCTE35-OUT=0xFC303...
#EXTINF:4.000,
1028/segment_239959.ts
#EXTINF:4.000,
1028/segment_239960.ts
#EXT-X-DATERANGE:ID="2415919105",START-DATE="2020-11-08T21:11:28.976Z",DURATION=29.988,SCTE35-OUT=0xFC303...
#EXTINF:4.000,
1028/segment_239961.ts
#EXTINF:4.000,
1028/segment_239962.ts
#EXTINF:4.000,
1028/segment_239963.ts
...
#EXT-X-DATERANGE:ID="2415919105",END-DATE="2020-11-08T21:11:48.976Z",SCTE35-IN=0xFC303...
#EXTINF:4.000,
1028/segment_239968.ts

#EXT-X-CUE-OUT

  • Use #EXT-X-CUE-OUT as the ad marker
  • Repeat a cue-out ad marker in the live stream's source manifest

When the source encoder schedules an upcoming ad break, it can also insert an #EXT-X-CUE-OUT cue-out marker into the source manifest. The marker's X-TYPE attribute indicates the type of ad marker; for early ad break notification, the value for X-TYPE is expected to be EABN. The marker's DURATION attribute must indicate the duration of the ad break. This marker is called an EABN cue-out.

At the actual start of the ad break, the source encoder must insert an #EXT-X-CUE-OUT cue-out marker into the source manifest. The marker's ID attribute must be the same as the corresponding EABN cue-out. This marker is called an immediate cue-out.

The following sample manifest contains one EABN cue-out, one immediate cue-out, and one cue-in:

#EXTM3U
#EXT-X-TARGETDURATION:4
#EXT-X-VERSION:7
#EXT-X-PROGRAM-DATE-TIME:2020-11-08T21:11:20.976Z
#EXT-X-MEDIA-SEQUENCE:239959
#EXT-X-DISCONTINUITY-SEQUENCE:2
#EXT-OATCLS-SCTE35:0xFC303...
#EXT-X-CUE-OUT:ID="2415919105",X-TYPE="EABN",DURATION=29.988
#EXTINF:4.000,
1028/segment_239959.ts
#EXTINF:4.000,
1028/segment_239960.ts
#EXT-OATCLS-SCTE35:0xFC303...
#EXT-X-CUE-OUT:ID="2415919105",DURATION=29.988
#EXTINF:4.000,
1028/segment_239961.ts
#EXTINF:4.000,
1028/segment_239962.ts
#EXTINF:4.000,
1028/segment_239963.ts
...
#EXT-X-CUE-IN:ID="2415919105"
#EXTINF:4.000,
1028/segment_239968.ts

DASH early ad break notification

To notify the API of an upcoming ad break so the API can prepare ads in advance, a DASH live stream manifest must repeat ad marker Event in the Main Period and the Ad Break Period.

The first appearance in the Main Period notifies the API of an upcoming ad break, and the second appearance in the Ad Break Period indicates the immediate start of the ad break.

The following is a sample manifest:

<MPD>
<Period id="1">
   <!-- Main Period -->
   <EventStream timescale="90000"  schemeIdUri="urn:scte:scte35:2013:xml">
     <Event duration="5400000" presentationTime="53460000" id="1">
       <scte35:SpliceInfoSection>
          <scte35:SpliceInsert outOfNetworkIndicator="true" spliceImmediateFlag="true">
            <scte35:BreakDuration autoReturn="true" duration="5400000"/>
            </scte35:SpliceInsert>
        </scte35:SpliceInfoSection>
      </Event>
    </EventStream>
   ...
</Period>

<Period start="PT9M54S" id="2">
    <!-- Ad Break Period -->
   <EventStream timescale="90000"  schemeIdUri="urn:scte:scte35:2013:xml">
     <Event duration="5400000" id="1">
       <scte35:SpliceInfoSection>
          <scte35:SpliceInsert outOfNetworkIndicator="true" spliceImmediateFlag="true">
            <scte35:BreakDuration autoReturn="true" duration="5400000"/>
            </scte35:SpliceInsert>
        </scte35:SpliceInfoSection>
      </Event>
    </EventStream>
   ...
</Period>

<Period start="PT10M54S" id="3">
    <!-- Main Period -->
    ...
</Period>
</MPD>

What's next

Learn how to complete specific Video Stitcher API tasks.