In a typical ad insertion workflow, MediaTailor dynamically transcodes ads to match the content stream, saves them, and stitches the ads into the live stream. Because this process happens only after MediaTailor receives the ad in a VAST response from the ad decision server (ADS), there is a delay for when the ad is available for stitching. If additional latency is introduced to the ad stitching workflow (either because of ADS timeout or other content or network issues), MediaTailor could partially fill the avail, or miss the ad break altogether.
To reduce the time needed to stitch ads into your content, you can use preconditioned ads. A preconditioned ad is one that you transcode before using it in MediaTailor ad insertion. Instead of providing URLs for the unconditioned ads to your ADS, you provide the URLs for the preconditioned ads. In its VAST response to the MediaTailor request, the ADS includes direct links to the preconditioned ads. By removing the transcoding part of ad stitching, MediaTailor needs to just save the ad and stitch it into the content stream. The ad stitching process with preconditioned ads reduces the time between when MediaTailor is made aware of an ad through the VAST response and when the ad is stitched into the content.
Alternatively, you can also use ad prefetching, which is when you configure MediaTailor to perform the ad stitching process at a scheduled time before the ad break is needed. For more information about ad prefetching, see Prefetching ads.
Preconditioned ads requirements
The following are requirements to consider when setting up an ad stitching workflow with preconditioned ads.
MediaFiles requirements
The VAST response that the ad server sends to MediaTailor must include MediaFiles that meet these requirements:
The ad (Creative) must have variants that conform to the bitrate variants of the
content stream.It's your responsibility to ensure that the VAST
response uses the right ad variants to match template manifests.
While using preconditioned ads can help make ad insertion more efficient, MediaTailor does not have the ability to manage the transcoding process to ensure that the media files for the ads are compatible with the content manifest specifications. If the ad doesn't match the content stream, MediaTailor could miss the insertion or the mismatch could cause the playback device to error.
Additionally, to be stitched into the content stream without MediaTailor transcoding, a
MediaFile must meet these requirements:
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It must be accessible on the public internet so that MediaTailor can download it.
It must use streaming delivery, denoted as
delivery="streaming"in the VAST response.It must be either a
.m3u8(for HLS) or.mpd(for DASH) file.
Example VAST response
From the following example VAST response, MediaTailor inserts the MediaFile with
the following URLs:
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For an HLS stream, MediaTailor uses
https://example-ad-origin.amazonaws.com/ad1/index_low.m3u8. This is the firstMediaFilewith streaming delivery and a supported file extension (.m3u8). -
For a DASH stream, MediaTailor uses
https://example-ad-origin.amazonaws.com/ad1/index.mpd. This is the firstMediaFilewith streaming delivery and a supported file extension (.mpd).
<?xml version="1.0" encoding="UTF-8"?> <VAST xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="3.0"> <Ad id="ad1"> <InLine> <AdSystem>ExampleAdSystem</AdSystem> <AdTitle>ad1</AdTitle> <Impression><![CDATA[https://example-impression.amazonaws.com]]></Impression> <AdServingId>de8e0d33-9c72-4d77-bb3a-f7e566ffc605</AdServingId> <Creatives> <Creative id="creativeId1" sequence="1"> <Linear skipoffset="00:00:05"> <Duration>00:00:30</Duration> <MediaFiles> <MediaFile delivery="progressive" width="1280" height="720" type="video/mp4" bitrate="533" scalable="true" maintainAspectRatio="true"><![CDATA[https://example-ad-origin.amazonaws.com/ad1/ad1.mp4]]></MediaFile> <MediaFile delivery="streaming" width="1280" height="720" type="application/dash+xml" bitrate="533" scalable="true" maintainAspectRatio="true"><![CDATA[https://example-ad-origin.amazonaws.com/ad1/index.mpd]]></MediaFile> <MediaFile delivery="streaming" width="640" height="360" type="application/x-mpegURL" bitrate="262" scalable="true" maintainAspectRatio="true"><![CDATA[https://example-ad-origin.amazonaws.com/ad1/index_low.m3u8]]></MediaFile> <MediaFile delivery="streaming" width="2560" height="1440" type="application/x-mpegURL" bitrate="1066" scalable="true" maintainAspectRatio="true"><![CDATA[https://example-ad-origin.amazonaws.com/ad1/index_high.m3u8]]></MediaFile> </MediaFiles> </Linear> </Creative> </Creatives> </InLine> </Ad> </VAST>
Ad manifest requirements
To use preconditioned ads, your parent and child ad manifests must meet these requirements:
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The manifest that's linked in the
Creativesection of the VAST response must be the parent ad manifest. -
The URLs for the child ad manifests must be relative paths.
-
The child ad manifests must be in the same directory as the parent manifest, at the same level. Child manifests can't be in a sub-directory or other location.
Example supported parent manifest
The following parent ad manifest contains relative URLs for child ad manifests. The child manifests are also in the same directory as the parent manifest.
#EXTM3U #EXT-X-STREAM-INF:BANDWIDTH=150000,RESOLUTION=416x234,CODECS="avc1.42e00a,mp4a.40.2" index_1.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=440000,RESOLUTION=416x234,CODECS="avc1.42e00a,mp4a.40.2" index_2.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=640000,RESOLUTION=640x360,CODECS="avc1.42e00a,mp4a.40.2" index_3.m3u8
Example unsupported parent manifest: subdirectories
The following parent ad manifest contains child manifests that are in sub-directories relative to the parent manifest. It is not a supported manifest for preconditioned ads.
#EXTM3U #EXT-X-STREAM-INF:BANDWIDTH=150000,RESOLUTION=416x234,CODECS="avc1.42e00a,mp4a.40.2" child/index_1.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=440000,RESOLUTION=416x234,CODECS="avc1.42e00a,mp4a.40.2" child/index_2.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=640000,RESOLUTION=640x360,CODECS="avc1.42e00a,mp4a.40.2" child/index_3.m3u8
Example unsupported parent manifest: absolute URLs
The following parent ad manifest contains child manifests with absolute URLs. It is not a supported manifest for preconditioned ads.
#EXTM3U #EXT-X-STREAM-INF:BANDWIDTH=150000,RESOLUTION=416x234,CODECS="avc1.42e00a,mp4a.40.2" https://example.mediatailor.us-west-2.amazonaws.com/index_1.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=440000,RESOLUTION=416x234,CODECS="avc1.42e00a,mp4a.40.2" https://example.mediatailor.us-west-2.amazonaws.com/index_2.m3u8 #EXT-X-STREAM-INF:BANDWIDTH=640000,RESOLUTION=640x360,CODECS="avc1.42e00a,mp4a.40.2" https://example.mediatailor.us-west-2.amazonaws.com/index_3.m3u8
Preconditioned ads workflow
The following is a basic description of how preconditioned ads work in an ad stitching workflow with MediaTailor. The first part of the workflow are actions that you must take to get set up for using preconditioned ads. The second part describes how MediaTailor processes the ads.
Part 1: Preconditioned ads set up
Complete the following steps to set up a workflow that uses preconditioned ads in MediaTailor.
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Use a transcoder service, such as AWS Elemental MediaConvert, to condition your creatives into variants that support the different bitrates, resolutions, and codecs of your template manifests.
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Provide the URLs for the pre-transcoded media files to your ADS, for use in VAST responses.
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Create your playback configuration in MediaTailor. To use preconditioned ads, select None for the Streaming media file conditioning setting in the configuration.
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Continue with your content delivery set up as you normally would.
Part 2: MediaTailor ad processing
MediaTailor ad stitching completes as described in How MediaTailor ad insertion works. When MediaTailor receives a VAST response from the ADS, it uses the following logic to determine what actions to take for the ads. This logic is dictated by the Streaming media file conditioning setting on the playback configuration.
-
When Streaming media file conditioning is set to Transcode, MediaTailor transcodes the media files with
progressivedelivery and stitches them into the manifest. If there aren't enough ads withprogressivedelivery media files to fill the avail, MediaTailor transcodes and uses those withstreamingdelivery. -
When Streaming media file conditioning is set to None, MediaTailor stitches ads with
streamingdelivery media files into the manifest without transcoding them. If there aren't enough ads withstreamingdelivery media files to fill the avail, MediaTailor transcodes and uses those withprogressivedelivery.
