Sparse Timed Metadata Tracks for Fragmentation-Safe Event Timing
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Solution Overview
Problem
The existing ISO/IEC base media file format (ISOBMFF) fragmentation and defragmentation processes fail to maintain the timing integrity of event message boxes in sparse timed metadata tracks, which are essential for synchronized media events in MPEG-DASH streaming.
Innovation Solution
Implement single-sample sparse timed metadata tracks where each segment or fragment includes only one metadata sample, with event message boxes using version 1 anchors tied to the track's earliest presentation time, ensuring timing integrity is maintained during fragmentation and defragmentation processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional ISOBMFF fragmentation and defragmentation processes are used on timed metadata tracks, then the media can be delivered in flexible segments, but the timing integrity of event message boxes is lost
Solution Approach 1:
The patent divides the timed metadata track into multiple segments, where each segment contains exactly one metadata sample. This segmentation approach allows flexible delivery of media segments while maintaining timing integrity because each segment's single metadata sample can be independently processed and its event message boxes timing can be accurately determined relative to that segment's presentation time.
Solution Approach 2:
The patent establishes timing anchors in advance by setting the presentation time of each metadata sample equal to the earliest presentation time of its containing segment. This preliminary timing establishment ensures that when segments are fragmented and reassembled, the event message boxes within each segment maintain their correct timing relationships without requiring complex post-processing.
2Quantity of substance
If multiple metadata samples are included in each segment, then the metadata track is more compact, but timing accuracy of event message boxes deteriorates during fragmentation
Solution Approach 1:
Instead of placing multiple metadata samples in each segment, the patent adopts a one-to-one mapping where each segment contains exactly one metadata sample. This approach prioritizes timing accuracy over metadata density, ensuring that each metadata sample's timing can be precisely determined from its containing segment's presentation time, even when fragmentation occurs.
Solution Approach 2:
The patent applies different timing strategies to different segments based on their individual characteristics. Each segment's single metadata sample uses that segment's earliest presentation time as its anchor, creating locally optimized timing relationships that maintain global timing accuracy across the entire fragmented stream.
3Ease of manufacture
If event message boxes use version 0 anchors tied to segment start time, then segmentation is simplified, but timing integrity fails during defragmentation
Solution Approach 1:
The patent pre-establishes the timing relationship between metadata samples and their containing segments by setting the metadata sample presentation time equal to the segment's earliest presentation time. This preliminary timing anchor is set before fragmentation occurs, ensuring that when segments are later reassembled through defragmentation, the event message boxes maintain their correct timing without requiring complex version 1 calculations.
Solution Approach 2:
Instead of having event message boxes reference segment start times (version 0) or track start times (version 1), the patent inverts the approach by having metadata samples serve as the primary timing anchors, with event message boxes deriving their timing from the metadata sample's presentation time. This inversion simplifies the fragmentation process while maintaining timing integrity.
Data Source
AI summary
Aspects of the disclosure provide methods, apparatuses, and non-transitory computer-readable storage mediums for receiving media data. One apparatus includes processing circuitry that receives a timed metadata track of a plurality of segments including a plurality of metadata samples. A duration of each of the plurality of segments is equal to a duration of a metadata sample included in the respective segment. A correct timing of each of the plurality of metadata samples is maintained during fragmentation and defragmentation processes that are performed on the timed metadata track. The processing circuitry determines a presentation time of one of the plurality of metadata samples. The processing circuitry processes event information included in one or more event message boxes included in the one of the plurality of metadata samples based on the presentation time of the one of the plurality of metadata samples.