UbikLoadPack Video Streaming Plugin 10.2.9

on 16 March ABR-Streaming, AD INSERTION, Apple HTTP Live Streaming, HLS, JMETER, JMETER-PLUGINS, MPEG-DASH and Tags: ApacheJMeter, HLS, JMETER, LOADTEST, PERFORMANCE, Video Streaming with 0 comments

We’re proud to announce the release of version 10.2.9 of our performance testing tool for Video Streaming servers (HLS, MPEG-DASH, HSS, HDS).

This release brings significant improvements for modern streaming formats, including enhanced HLS support with EXT-X-MAP and EXT-X-START tags, low-latency DASH optimizations, fixes for HLS Interstitials ad insertion, along with bug fixes that improve test accuracy and reliability

Let’s explore what this version brings to your performance testing workflow.

New Features

EXT-X-MAP Support for HLS

What is EXT-X-MAP?

The EXT-X-MAP tag is a crucial component in modern HLS streams, particularly for fMP4 (fragmented MP4) based content. It specifies where to find the Media Initialization Section, which contains essential codec and track information required to decode media segments.

The EXT-X-MAP tag specifies how to obtain the Media Initialization Section required to parse the applicable Media Segments. It applies to every Media Segment that appears after it in the Playlist until the next EXT-X-MAP tag or until the end of the Playlist.

Source: HLS documentation §4.4.4.5

This is increasingly common in:

Low-Latency HLS (LL-HLS) streams
CMAF (Common Media Application Format) based content
Streams using fMP4 instead of MPEG-TS

The spec mandates that each fMP4 Segment in a Media Playlist MUST have an EXT-X-MAP tag applied to it, making this tag essential for modern HLS implementations.

How the plugin handles it

When the plugin encounters EXT-X-MAP tags in variant playlists, it now properly downloads initialization segments before processing media chunks. This is reflected in new sample types in your test results:

Sample Type	Description
`INIT_SEGMENT_VIDEO`	Video initialization segment
`INIT_SEGMENT_AUDIO`	Audio initialization segment
`INIT_SEGMENT_SUBTITLES`	Subtitles initialization segment

For streams with interstitials (ad insertion), dedicated sample types are also available:

Sample Type	Description
`INIT_SEGMENT_VIDEO_INTERSTITIALS`	Video init segment for interstitials
`INIT_SEGMENT_AUDIO_INTERSTITIALS`	Audio init segment for interstitials
`INIT_SEGMENT_SUBTITLES_INTERSTITIALS`	Subtitles init segment for interstitials

Manifest example

#EXTM3U
#EXT-X-VERSION:7
#EXT-X-TARGETDURATION:6
#EXT-X-MEDIA-SEQUENCE:1
#EXT-X-MAP:URI="init_video.mp4"
#EXTINF:6.000,
segment1.m4s
#EXTINF:6.000,
segment2.m4s
#EXTINF:6.000,
segment3.m4s

Processing flow

This feature ensures your load tests accurately simulate how modern video players behave with fMP4-based HLS streams.

DASH: availabilityTimeOffset=”INF” support

Understanding availabilityTimeOffset

In DASH streaming, the availabilityTimeOffset attribute controls when segments become available relative to their official availability time. A value of "INF" (infinity) indicates that all segments are immediately available as soon as the manifest is published.

This is commonly used for:

Live streams with very low latency requirements
Edge caching scenarios
Streams where segments are pre-generated

Manifest example

<MPD xmlns="urn:mpeg:dash:schema:mpd:2011" 
     type="dynamic" 
     minimumUpdatePeriod="PT2S">
  <Period start="PT0S">
    <AdaptationSet contentType="video">
      <SegmentTemplate 
          timescale="90000" 
          duration="180000"
          availabilityTimeOffset="INF"
          initialization="init-$RepresentationID$.m4s" 
          media="segment-$RepresentationID$-$Number$.m4s"/>
      <Representation id="1" bandwidth="2000000"/>
    </AdaptationSet>
  </Period>
</MPD>

Segment Availability Timeline

With availabilityTimeOffset="INF", all segments are immediately available. However, to avoid overwhelming the server with requests and triggering HTTP 429 (Too Many Requests) errors, the plugin waits for half the chunk duration before requesting the next segment. This provides a realistic playback simulation while respecting server rate limits.

EXT-X-START Support for Live HLS

What changed ?

The plugin now properly handles the EXT-X-START tag in live HLS manifests. This tag specifies the preferred starting point within the playlist using the TIME-OFFSET attribute.

The EXT-X-START tag indicates a preferred point at which to start playing a Playlist. By default, clients SHOULD start playback at this point when beginning a playback session. […] The value of TIME-OFFSET is a signed-decimal-floating-point number of seconds. A positive number indicates a time offset from the beginning of the Playlist. A negative number indicates a negative time offset from the end of the last Media Segment in the Playlist.

Source: HLS documentation §4.4.2.2

Behavior

TIME-OFFSET Value	Starting Point
Positive (e.g., `10.0`)	Start 10 seconds from the beginning of the playlist
Negative (e.g., `-30.0`)	Start 30 seconds before the live edge

Previous behavior

The plugin always started 3 chunks before the end, ignoring the manifest’s recommendation.

New behavior

The plugin respects the TIME-OFFSET value, providing a more realistic simulation of actual player behavior.

Manifest examples

Positive offset

#EXTM3U
#EXT-X-TARGETDURATION:6
#EXT-X-VERSION:6
#EXT-X-MEDIA-SEQUENCE:295253097
#EXT-X-START:TIME-OFFSET=25.00
#EXT-X-MAP:URI="/segments/init_video.mp4"
#EXT-X-PROGRAM-DATE-TIME:2026-02-19T16:29:44.916045732Z
#EXTINF:6.00000,
/segments/video_295253097.mp4
#EXTINF:6.00000,
/segments/video_295253098.mp4
#EXTINF:6.00000,
/segments/video_295253099.mp4
#EXTINF:6.00000,
/segments/video_295253100.mp4
#EXTINF:6.00000,
/segments/video_295253101.mp4
#EXTINF:6.00000,
/segments/video_295253102.mp4
#EXTINF:6.00000,
/segments/video_295253103.mp4
#EXTINF:6.00000,
/segments/video_295253104.mp4
#EXTINF:6.00000,
/segments/video_295253105.mp4
#EXTINF:6.00000,
/segments/video_295253106.mp4

In this example, with TIME-OFFSET=25.00, playback starts 25 seconds after manifest start, which corresponds to segment video_295253101.

Negative offset

#EXTM3U
#EXT-X-TARGETDURATION:6
#EXT-X-VERSION:6
#EXT-X-MEDIA-SEQUENCE:295253093
#EXT-X-START:TIME-OFFSET=-25.00
#EXT-X-MAP:URI="/segments/init_video.mp4"
#EXT-X-PROGRAM-DATE-TIME:2026-02-19T16:29:20.324476576Z
#EXTINF:6.00000,
/segments/video_295253093.mp4
#EXTINF:6.00000,
/segments/video_295253094.mp4
#EXTINF:6.00000,
/segments/video_295253095.mp4
#EXTINF:6.00000,
/segments/video_295253096.mp4
#EXTINF:6.00000,
/segments/video_295253097.mp4
#EXTINF:6.00000,
/segments/video_295253098.mp4
#EXTINF:6.00000,
/segments/video_295253099.mp4
#EXTINF:6.00000,
/segments/video_295253100.mp4
#EXTINF:6.00000,
/segments/video_295253101.mp4
#EXTINF:6.00000,
/segments/video_295253102.mp4

In this example, with TIME-OFFSET=25.00, playback starts 25 seconds before the live edge, which corresponds to segment video_295253098.

New utility : Advanced Assertions with ULPVideoAnalysisUtils

Version 10.2.9 introduces the ULPVideoAnalysisUtils utility class, a powerful new tool for creating custom assertions (using JSR223 and groovy for example) in your video streaming performance tests.

What it enables

This utility provides programmatic access to streaming-specific data, allowing you to:

Identify request types: Distinguish between manifest requests, chunk downloads, and aggregated streaming results
Extract response headers: Retrieve specific header values for CDN analysis and validation
Access Quality of experience metrics: Get lag ratio, buffer fill duration, and other Quality of Experience indicators
Override response codes: Customize error codes based on your business logic for better reporting

Quick example

In the following example, an error will be present in the VideoStreamingSampleResult if the lag ratio exceeds 5%

import com.ubikingenierie.jmeter.plugin.video.client.ULPVideoAnalysisUtils

if (ULPVideoAnalysisUtils.isVideoStreamingSampleResult(prev)) {
    float lagRatio = ULPVideoAnalysisUtils.getLagRatio(prev)
    if (lagRatio > 5.0) {
        AssertionResult.setFailure(true)
        ULPVideoAnalysisUtils.overrideResponseCodeAndMessage(prev, "LAG_TOO_HIGH", 
            "Lag ratio " + lagRatio + "% exceeds 5% threshold")
    }
}

Why it matters

With ULPVideoAnalysisUtils, you can implement sophisticated Quality of experience pased pass/fail criteria directly in your JMeter test plans. This means:

Custom validation rules based on real user experience metrics
Better visibility in HTML reports with custom response codes
Differentiated assertions for manifests vs. chunks vs. complete sessions

A dedicated blog post covering this feature in depth will be published soon. Stay tuned for detailed examples, best practices, and advanced use cases for building production-grade video streaming performance tests.

Bug Fixes

Accurate Error Reporting: NOT_ENOUGH_CHUNKS Preserved

The issue

When a stream didn’t have enough chunks buffered before starting playback, the NOT_ENOUGH_CHUNKS status was being overwritten by a generic PLAY_ERROR, making it difficult to diagnose buffer-related issues.

The fix

The NOT_ENOUGH_CHUNKS status is now correctly preserved and reported in test results, enabling you to:

Identify buffering issues in your streams
Distinguish between different types of playback failures
Fine-tune your CDN and origin configurations

HLS Audio-Only Live Streams

The plugin now correctly handles live HLS manifests containing only audio tracks. This is essential for testing:

Live radio streaming
Podcasts delivered via HLS
Audio-only simulcast streams

VOD Offset Validation

Improvements

Two important validations have been added for VOD (Video on Demand) streams:

Offset exceeds duration: If you specify a start offset greater than the video duration, the plugin now returns a clear error instead of failing silently.
Negative offset rejected: Negative offset values are no longer accepted for VOD streams, preventing configuration errors.

Scenario	Previous Behavior	New Behavior
Offset > Video duration	Silent failure	Clear error message
Negative offset	Unpredictable	Validation error

Bandwidth Consistency in AUTO and MANUAL Modes

The issue

In certain edge cases, the plugin was incorrectly switching bandwidth during playback even when configured in AUTO or MANUAL mode. This violated the expected behavior where:

AUTO mode: The plugin selects the highest available bandwidth at the start and maintains it throughout the session
MANUAL mode: The plugin uses the user-specified bandwidth consistently

The fix

The bandwidth selection logic has been corrected to ensure stable bandwidth throughout the entire streaming session when using AUTO or MANUAL modes. The selected bandwidth is now properly locked at session start and never changes mid-stream.

Mode	Behavior	Status
AUTO	Highest bandwidth, constant	Fixed
MANUAL	User-specified, constant	Fixed
ABR (Adaptive)	Dynamic adjustment	Unchanged

This fix ensures your performance tests accurately measure server performance at consistent quality levels, providing more reliable and reproducible results.

Correct Error Propagation in VideoStreamingSampleResult

The issue

When an error occurred during chunk download, the parent VideoStreamingSampleResult was incorrectly marked as successful while containing a failed child sample. This led to:

Misleading success rates in reports
Hidden errors in test analysis
Incorrect APDEX calculations

The fix

The plugin now correctly propagates errors :

Parent sample is marked as failed when any child fails
No orphaned child samples on error
Accurate success/failure metrics

HLS Interstitials: Playback Accuracy Fixes

This release addresses three issues in HLS Interstitials support, ensuring accurate simulation of ad insertion scenarios during performance testing.

X-ASSET-LIST: Multiple Assets Now Properly Retrieved

The issue

When an interstitial event used X-ASSET-LIST pointing to a JSON containing multiple ad assets, the plugin was only downloading the first asset, ignoring subsequent ones. This led to incomplete ad simulation and inaccurate load metrics.

The value of the X-ASSET-LIST is a quoted-string URL to a JSON object. The JSON object must contain a key/value pair whose key is “ASSETS” and whose value is a JSON array of Asset-Description JSON objects

Source : HLS interstitials specification

Example Asset List

{
    "ASSETS": [
        { "URI": "https://ads.example.com/bumper.m3u8", "DURATION": 5 },
        { "URI": "https://ads.example.com/ad1.m3u8", "DURATION": 30 },
        { "URI": "https://ads.example.com/ad2.m3u8", "DURATION": 15 }
    ]
}

The fix

The plugin now correctly iterates through all assets in the X-ASSET-LIST JSON response, downloading each manifest and its associated segments sequentially. This ensures your load tests accurately reflect the full ad pod delivery, providing realistic traffic patterns for CDN and origin server evaluation.

Scenario	Previous Behavior	New Behavior
3-asset ad pod	Only 1st asset downloaded	All 3 assets downloaded
Pre-roll + mid-roll assets	Partial simulation	Complete ad sequence

X-RESUME-OFFSET: Main Content Chunks Correctly Skipped

The issue

The X-RESUME-OFFSET attribute specifies how many seconds of main content should be skipped after interstitial playback. When this value was greater than 0 or absent (defaulting to 0 for VOD), the plugin was incorrectly downloading main content chunks that should have been replaced by the interstitial content.

The value of X-RESUME-OFFSET is a decimal-floating-point of seconds that specifies where
primary playback should resume following the playback of the interstitial. It is expressed as a
time offset from where the interstitial playback was scheduled on the primary player timeline. A
typical value for X-RESUME-OFFSET is zero. If the X-RESUME-OFFSET is not present, the play-
er uses the duration of interstitial playback for the resume offset, which is appropriate for live
playback where playback is to be kept at a constant delay from the live edge, or for VOD play-
back where the HLS interstitial is intended to replace content in the primary asset.

Source : HLS interstitials specification

The problem illustrated

Main content timeline:  [chunk1][chunk2][chunk3][chunk4][chunk5][chunk6]
                               ↑               ↑
                          interstitial    resume point
                            start        (X-RESUME-OFFSET)

Previous: Downloaded chunk2, chunk3, chunk4 AND interstitial content
Fixed:    Downloads only interstitial content, skips chunk2-4

The fix

The plugin now properly respects X-RESUME-OFFSET:

Calculates which main content chunks fall within the interstitial window
Skips downloading those chunks entirely
Resumes main content download at the correct position after interstitial playback

This fix ensures accurate byte counts, realistic bandwidth consumption, and proper server load distribution between main content and ad servers.

VOD Streams: Pre-Roll AND Mid-Roll Interstitials Now Processed

The issue

For VOD streams containing both pre-roll (CUE="PRE") and mid-roll interstitials, the plugin was only processing pre-roll content, completely ignoring mid-roll ad breaks. This resulted in:

Incomplete ad server load testing
Missing revenue-critical mid-roll impressions in simulations
Inaccurate total playback duration metrics

Manifest example

#EXTM3U
#EXT-X-TARGETDURATION:6
#EXT-X-PLAYLIST-TYPE:VOD
#EXT-X-PROGRAM-DATE-TIME:2026-03-01T10:00:00.000Z

#EXT-X-DATERANGE:ID="preroll",CLASS="com.apple.hls.interstitial",START-DATE="2026-03-01T10:00:00.000Z",CUE="PRE",X-ASSET-URI="https://ads.example.com/preroll.m3u8",DURATION=15.0

#EXTINF:6.000,
segment1.ts
#EXTINF:6.000,
segment2.ts

#EXT-X-DATERANGE:ID="midroll1",CLASS="com.apple.hls.interstitial",START-DATE="2026-03-01T10:00:12.000Z",X-ASSET-URI="https://ads.example.com/midroll.m3u8",DURATION=30.0

#EXTINF:6.000,
segment3.ts
...
#EXT-X-ENDLIST

The fix

The plugin now maintains proper state tracking across the entire VOD playback session, ensuring:

Pre-roll interstitials are played before main content
Mid-roll interstitials are triggered at their designated START-DATE
Post-roll interstitials (if present) are processed after main content

Interstitial Type	Previous Behavior	New Behavior
Pre-roll (`CUE="PRE"`)	Processed	Processed
Mid-roll	Ignored	Processed
Post-roll (`CUE="POST"`)	Ignored	Processed

This fix is essential for accurately simulating viewer journeys through ad-supported VOD content, ensuring your performance tests reflect real-world ad delivery patterns.

Summary

Version 10.2.9 brings crucial improvements for testing modern streaming architectures:

Feature	Benefit
EXT-X-MAP support	Accurate simulation of fMP4/CMAF HLS streams
availabilityTimeOffset=”INF”	Proper low-latency DASH testing
EXT-X-START	Realistic live stream playback positioning
NOT_ENOUGH_CHUNKS fix	Better error diagnosis
Audio-only live HLS	Testing podcasts and radio streams
VOD offset validation	Prevent misconfigurations
Error propagation fix	Accurate success/failure metrics
Bandwidth consistency fix	Reliable AUTO/MANUAL mode testing
ULPVideoAnalysisUtils	Custom Quality of experience based assertions
X-ASSET-LIST multi-asset fix	Complete ad pod simulation
X-RESUME-OFFSET fix	Accurate main content skipping
VOD pre/mid-roll fix	Full interstitial coverage

Getting Started

Upgrade to version 10.2.9 to take advantage of these improvements. For detailed documentation and examples, visit our support portal.

References

HLS Specifications

RFC 8216bis – HTTP Live Streaming 2nd Edition: draft-pantos-hls-rfc8216bis-20
- Section 4.4.4.5: EXT-X-MAP tag specification
- Section 4.4.2.2: EXT-X-START tag specification
- Section 3.1.2: Fragmented MPEG-4 requirements

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UbikLoadPack Video Streaming Plugin 10.2.9

New Features

EXT-X-MAP Support for HLS

What is EXT-X-MAP?

How the plugin handles it

Manifest example

Processing flow

DASH: availabilityTimeOffset=”INF” support

Understanding availabilityTimeOffset

Manifest example

Segment Availability Timeline

EXT-X-START Support for Live HLS

What changed ?

Behavior

Previous behavior

New behavior

Manifest examples

Positive offset

Negative offset

New utility : Advanced Assertions with ULPVideoAnalysisUtils

What it enables

Quick example

Why it matters

Bug Fixes

Accurate Error Reporting: NOT_ENOUGH_CHUNKS Preserved

The issue

The fix

HLS Audio-Only Live Streams

VOD Offset Validation

Improvements

Bandwidth Consistency in AUTO and MANUAL Modes

The issue

The fix

Correct Error Propagation in VideoStreamingSampleResult

The issue

The fix

HLS Interstitials: Playback Accuracy Fixes

X-ASSET-LIST: Multiple Assets Now Properly Retrieved

The issue

Example Asset List

The fix

X-RESUME-OFFSET: Main Content Chunks Correctly Skipped

The issue

The problem illustrated

The fix

VOD Streams: Pre-Roll AND Mid-Roll Interstitials Now Processed

The issue

Manifest example

The fix

Summary

Getting Started

References

HLS Specifications

About UbikLoadPack :

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Latest posts

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