MBMS Synchronization via Segment Receipt Timestamps
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Solution Overview
Problem
The synchronization of multimedia content playback between a server and user devices in MBMS services is challenging due to variable latency times and unsynchronized internal clocks, leading to errors in data segment availability and playback timing, especially during live broadcasts and when devices move out of network coverage.
Innovation Solution
A method involving a multimedia content server and user devices that includes receiving and buffering multimedia content segments, requesting and transmitting synchronization data with an HTTP response or file, which includes an identifier of the last received segment and its receipt time, allowing the user device to determine the start time of segments and request synchronization upon errors, ensuring accurate playback timing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If MBMS service processes multimedia streams with variable latency and unsynchronized clocks, then network loading is reduced through point-to-multipoint transmission, but synchronization accuracy deteriorates causing playback errors
Solution Approach 1:
The server transmits synchronization data containing the identifier and receipt time of the last received segment back to the user device. This feedback mechanism enables the device to calculate timing adjustments and resynchronize its playback clock with the server's timing, resolving the synchronization accuracy issue while maintaining efficient point-to-multipoint transmission
Solution Approach 2:
The system performs preliminary synchronization by transmitting synchronization data before playback errors occur. The user device uses this advance timing information to adjust its playback timing in anticipation of synchronization drift, preventing playback errors before they happen
2Adaptability or versatility
If user devices perform processing operations on multimedia streams, then content processing capability is improved, but variable latency times increase causing synchronization errors
Solution Approach 1:
The server measures the actual time taken for processing operations and includes this synchronization data in the response. This feedback allows the user device to compensate for the variable latency introduced by processing operations, maintaining accurate synchronization despite the time loss
3Ease of operation
If user devices operate independently without continuous synchronization, then device autonomy is improved, but playback timing accuracy deteriorates during network transitions
Solution Approach 1:
The system implements periodic synchronization by transmitting synchronization data at regular intervals or triggered by specific events such as network transitions. This periodic feedback maintains timing accuracy without requiring continuous synchronization, preserving device autonomy while ensuring playback timing precision during network changes
Data Source
AI summary
A method for playing back an item of multimedia content by user devices, the method including steps of: receiving segments of an item of multimedia content by a server, storing the received segments in a buffer memory, transmitting a segment request from a multimedia player of a user device to the server, and transmitting, in response, a requested segment from the server to the multimedia player, if the segment is present in the buffer memory, transmitting a request for synchronization data from the multimedia player to the server, and transmitting, in response to the request, synchronization data from the server to the multimedia player, the data including an identifier of a last segment received, and a datum defining the time of receipt of the last segment by the user's device.