Feature: MPEG-5 LCEVC Scalable support #4572

v-nova-romas · 2024-09-20T12:31:55Z

Adds MPEG-5 LCEVC scalable support into dash.js to enable playback of ABR profiles generated by LCEVC enhancement via a separate adaptation set.

This approach creates LCEVC representations which are dependent upon native codec representations (by using dependencyId). LCEVC enhancement representations are contained in a 2nd Adaptation Set and linked to the base representations in the 1st Adaptation Set. The outcome is the ability to play adaptive streaming content where one or more higher resolution profiles are generated by applying LCEVC enhancement to existing conventional profiles saving up to 70% bitrate compared to using conventional standalone native profiles.

There is a new section in dash.js samples for MPEG-5 Part 2 LCEVC where the scalable implementation is demonstrated.

Updated references to track to representation

Removed section on shorter buffers for demoing purposes

dsilhavy · 2024-09-23T11:39:18Z

@v-nova-romas Thank you for your PR. Can you please merge the latest changes from development into your PR. Thanks

v-nova-romas · 2024-09-23T13:13:33Z

Hi @dsilhavy Thank you, I have merged the latest changes

…vcScalableSupport

stschr · 2024-10-15T12:26:16Z

src/dash/vo/Representation.js

        this.startNumber = 1;
        this.timescale = 1;
        this.width = NaN;
+        this.dependentRepresentation = null


all member attributes in this constructor are sorted alphabetically.
Can you move this new entry?

Hi @stschr Thank you for taking the time to review the PR!

the new entry should now be sorted alphabetically

stschr · 2024-10-15T12:46:53Z

src/streaming/constants/Constants.js

    COMMON_ACCESS_TOKEN_HEADER: 'common-access-token',
    DASH_ROLE_SCHEME_ID : 'urn:mpeg:dash:role:2011',
+
+    ENHANCEMENT_CODECS: ['lvc1'],


With this code, 'lvc1' gets always considered as supported by src/streaming/utils/Capabilities.js#L141
However, shouldn't we reject this 4CC if lcevc_dec.js is not registered as extension?

Thank you, agreed! I would like to modify Capabilities.js#L141 to also check if lcevc_dec.js is loaded, and reject otherwise.

May I ask for clarification regarding registered as extension - is there a way in dash.js to register lcevc_dec.js as a loaded extension? I could check if window.LCEVCdec is defined but I am wondering if there is a more idiomatic way.

stschr · 2024-10-15T12:52:24Z

src/streaming/models/CmcdModel.js

            ot = CmcdObjectType.AUDIO;
        }
+        if (request.mediaType === Constants.ENHANCEMENT) {
+            ot = 'e';


Maybe not an issue, but where does this magic constant string come from? Is it allowed by Cmcd-spec? (@dsilhavy )

Originally we have considered that the enhancement doesn't quite fit under existing Cmcd Object Types. However, after looking at the Cmcd-spec it seems that tokens not defined in the spec (eg. e) would be discarded by a Cmcd server.

I would like to assign the enhancement ot to CmcdObjectType.OTHER. Do you think this would be a good approach?

I have set the enhancement ot to CmcdObjectType.OTHER.

Thank you!

stschr · 2024-10-15T13:26:58Z

src/dash/models/DashManifestModel.js

                }
+                if (realRepresentation.hasOwnProperty(DashConstants.DEPENDENCY_ID)) {
+                    voRepresentation.dependentRepresentation = new Representation();
+                    voRepresentation.dependentRepresentation.id = realRepresentation[DashConstants.DEPENDENCY_ID].toString();


I think we should handle the case when @dependencyId contains multiple @id valeus (as whitespace separated list):

@dsilhavy : What about added this to the capability checks, i.e. rejecting any Representation with more than one entry in this attribute?

Thank you, great idea! We would like to reject the representation and log it in the console when @dependencyId contains multiple @id values as it would most likely indicate an error with the packager. Do you think this would be a good way to approach it?

dsilhavy · 2024-11-04T10:03:22Z

@v-nova-romas Thank you for keeping this PR up to date. As this PR requires design changes in dash.js and I would like to carefully evaluate them, I need to move this PR to the milestone of v5.1. For v5 we have a working sample for LCEVC (https://reference.dashif.org/dash.js/nightly/samples/index.html#MPEG5Part2LCEVC). My apologies for the delay.

…calableSupport

- enhancement can be enabled/disabled - array of supported enhancement codecs can be extended

dsilhavy · 2025-08-25T08:59:45Z

Related draft IOP document: https://docs.google.com/document/d/1ImwRa2XRG0Amr5o9WA176scmAgeVnzPLhXW7IyWvE8Q/edit?tab=t.0#heading=h.sazim4co0skw

dsilhavy

Additional review comments:

Please make sure to adjust the index.d.ts to add newly added functions and classes
Consider adding a LCEVC testvector to our list of smoke vectors for functional tests: https://github.com/Dash-Industry-Forum/dash.js/blob/development/test/functional/config/test-configurations/streams/smoke.json

docs/lcevc/README.md

dsilhavy · 2024-09-25T14:47:30Z

docs/lcevc/dependent-representations.png

Can you please create a higher resolution export of this diagram. Ideally, can you also provide the source files for it?

Added a higher resolution export and source files for the diagram, thank you!

dsilhavy · 2024-09-25T14:47:34Z

docs/lcevc/enhancement-stream-processor.png

Can you please create a higher resolution export of this diagram. Ideally, can you also provide the source files for it?

Added a higher resolution export and source files for the diagram, thank you!

dsilhavy · 2024-09-27T06:30:26Z

samples/lcevc-dual-track/lcevc-dual-track-debug.html

Please place all lcevc related sample files into a root folder lcevc located in samples. You can create additional subfolders in there

Hi @dsilhavy ! Thank you for taking the time to review the PR!

I have moved all sample files to a root folder lcevc.

dsilhavy · 2024-09-27T06:30:35Z

samples/lcevc-dual-track/lcevc-dual-track.html

Please place all lcevc related sample files into a root folder lcevc located in samples. You can create additional subfolders in ther

Moved all sample files to a root folder lcevc, thank you!

dsilhavy · 2025-08-25T09:57:12Z

src/streaming/StreamProcessor.js

+            // Pass quality change on enhanced representation
+            enhancementStreamProcessor.prepareQualityChange(e);
+        }
+        else if (e.newRepresentation.mediaInfo.type !== e.oldRepresentation.mediaInfo.type) {


Can this check and the one after be more explicit? Like checking directly for enhancement. I don't quite the purpose here

The check has been moved to new private function _prepareQualityChangeForEnhancementStreamProcessor and made more explicit, thank you!

Please let me know if the new check is suitable

dsilhavy · 2025-08-25T09:59:55Z

src/streaming/StreamProcessor.js

    }

+    function getAbrRepresentation() {
+        return representationController ? representationController.getCurrentRepresentation(false) : null;


Do we need this function if we already have getRepresentation

I’ve removed this function, thank you! Please let me know if this looks suitable.

src/streaming/controllers/AbrController.js

dsilhavy · 2025-08-25T10:07:29Z

src/streaming/controllers/ScheduleController.js

        setCheckPlaybackQuality,
        setInitSegmentRequired,
        setLastInitializedRepresentationId,
+        setup,


Why do we need to expose the setup method?

There is a bit of logic in StreamProcessor.js _prepareQualityChangeForEnhancementStreamProcessor function that is responsible for starting and stopping the enhancement StreamProcessor when it is not needed.

In the current implementation, scheduleController.reset() is used to stop it. However, reset() clears the streamInfo of the scheduleController, and setup() is needed to set the streamInfo again.

I have tried the alternative of using startScheduleTimer and clearScheduleTimer methods of ScheduleController, but it seems we need to call resetInitialSettings() for it to work as expected, however it is also not exported.

Do you think this approach is suitable? Thank you!

dsilhavy · 2025-08-25T10:09:42Z

src/streaming/utils/Capabilities.js

        }

+        const enhancementCodecs = settings.get().streaming.enhancement.codecs;
+        if (settings.get().streaming.enhancement.enabled && basicConfiguration.codec.includes('video') && enhancementCodecs.some(cdc => basicConfiguration.codec.includes(cdc))) {


Use Constants for type: Constants.Video

Do we need to limit this to video?

Removed the limitation to video, thank you!

- Move logic to a separate private function - Make check more explicit

- Remove getCurrentRepresentation overload - Add getCurrentDependentRepresentation

dsilhavy · 2025-09-27T06:47:53Z

@v-nova-romas Thank you for addressing the comments. Please leave a short comment here once you are done with all your changes then I will have a look again and answer your remaining questions/comments.

v-nova-romas · 2025-09-29T22:14:01Z

Thank you @dsilhavy ! I have gone through and made all the changes. Thank you so much for taking the time to review the PR! I would love to hear your thoughts on the updates whenever you have a chance.

dsilhavy

Thank you for the changes, left some remaining comments from my side. Can you please also merge the latest changes from the development branch into your PR

samples/dash-if-reference-player/index.html

samples/dash-if-reference-player/app/css/main.css

src/dash/controllers/RepresentationController.js

src/dash/models/DashManifestModel.js

src/streaming/ExternalMediaSource.js

src/streaming/controllers/AbrController.js

dsilhavy · 2025-10-15T08:03:20Z

@v-nova-romas I see you are already working on the changes. Can you please leave a short note here again once you addressed all issues and the PR is ready for review again.

…cevcScalableSupport

v-nova-romas · 2025-10-17T18:21:25Z

@dsilhavy Thank you very much! I have addressed all comments and merged the latest changes from the development branch. I would love to hear your thoughts whenever you have a chance! Thanks!

dsilhavy · 2025-10-22T13:41:42Z

Thanks @v-nova-romas this looks good to me. I will merge it now

v-nova-romas and others added 3 commits September 13, 2024 11:17

Feature: MPEG-5 LCEVC Scalable support

02342be

Update README.md

b390b65

Updated references to track to representation

Update README.md

34b02d8

Removed section on shorter buffers for demoing purposes

dsilhavy added this to the 5.0.0 milestone Sep 23, 2024

Merge branch 'development' into feature/AddLcevcScalableSupport

1397f4b

dsilhavy requested review from dsilhavy and stschr September 25, 2024 05:17

v-nova-romas added 4 commits October 1, 2024 15:02

Merge remote-tracking branch 'origin/development' into feature/AddLce…

3538ead

…vcScalableSupport

Update tests after merging latest changes from development

7ba8123

Merge branch 'development' into feature/AddLcevcScalableSupport

ef8e0dd

Merge branch 'development' into feature/AddLcevcScalableSupport

e909c28

stschr reviewed Oct 15, 2024

View reviewed changes

Sort member attributes alphabetically

ac687cc

dsilhavy modified the milestones: 5.0.0, 5.1.0 Nov 4, 2024

v-nova-romas added 3 commits November 21, 2024 15:57

Merge branch 'development' into feature/AddLcevcScalableSupport

4a3f963

Merge branch 'development' into feature/AddLcevcScalableSupport

064329d

Update dash.js lib location in Sample pages

d2c98d4

dsilhavy moved this to Selected for Development in dash.js Version 5.1.0 Jun 12, 2025

v-nova-romas and others added 3 commits July 30, 2025 11:22

Merge branch 'Dash-Industry-Forum:development' into feature/AddLcevcS…

17ce0fa

…calableSupport

Set enhancement to CmcdObjectType.OTHER

49dc8bd

Make enhancement configurable via Settings.js

b800633

- enhancement can be enabled/disabled - array of supported enhancement codecs can be extended

dsilhavy requested changes Aug 25, 2025

View reviewed changes

v-nova-romas added 10 commits September 9, 2025 13:43

Provide reset method in ExternalMediaSource.js

66ebf32

Create _prepareQualityChangeForEnhancementStreamProcessor

ad70430

- Move logic to a separate private function - Make check more explicit

Remove limitation to video in Capabilities.js

83f31f2

Adjust index.d.ts definitions to add new functions and classes

83d8166

Adjust index.d.ts to include enhancement

dcd493f

Add higher resolution exports and source files for diagrams

c655991

Remove getCurrentRepresentation overload

b900f12

- Remove getCurrentRepresentation overload - Add getCurrentDependentRepresentation

Remove getAbrRepresentation function

1a5b1db

Do not resolve dependency in _addRepresentationSwitch

64ec29b

Remove documentation to be moved to gh-pages branch

d46bc04

v-nova-romas mentioned this pull request Sep 25, 2025

Documentation: MPEG-5 LCEVC Scalable support #4854

Merged

v-nova-romas added 3 commits September 25, 2025 15:30

Do not include compatible MediaInfos

4622811

Update unit tests to pass

f43608f

Accept whitespace-separated list of values for dependencyId

12c2205

dsilhavy requested changes Oct 13, 2025

View reviewed changes

v-nova-romas added 4 commits October 14, 2025 11:00

Make _getCurrentDependentRepresentation private

fa10394

Add comment for multiple dependency ids

2627ca9

Make UI Checkbox more descriptive

3e363e4

Trigger GitHub PR refresh

6f7423a

v-nova-romas added 4 commits October 15, 2025 12:06

Reuse reset function in ExternalMediaSource constructor

868b4bf

Fix UI buttons in controlbar being shifted up

d6a8865

Merge remote-tracking branch 'upstream/development' into feature/AddL…

68d2584

…cevcScalableSupport

Cleanup after merge

8ef5c85

dsilhavy merged commit 6dee0b1 into Dash-Industry-Forum:development Oct 22, 2025
2 checks passed

github-project-automation bot moved this from Selected for Development to Done in dash.js Version 5.1.0 Oct 22, 2025

Feature: MPEG-5 LCEVC Scalable support #4572

Feature: MPEG-5 LCEVC Scalable support #4572

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v-nova-romas commented Sep 20, 2024

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