Media Data Offset Time Synchronization During Seek Operations
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Solution Overview
Problem
During 'seek', 'fast-forward', 'fast-rewind', and other non-regular-play operations in media data processing, the local time and reference time adjustments lead to loss of time reference for buffered media data, typically resulting in data being dropped or flushed out of buffers.
Innovation Solution
A method and system that compute and stamp an offset time using the reference and local times, allowing immediate availability of media data for processing and adjusting the media data flow according to the expected presentation time, thereby maintaining synchronization and rate control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If local time and reference time are adjusted during seek operations, then the client can access media data from random locations, but the buffered media data loses its time reference and must be dropped or flushed
Solution Approach 1:
The system pre-computes and stores a mapping between presentation timestamps (PTS) and display timestamps (DTS) that accounts for potential time reference changes. This preliminary preparation allows the system to quickly adjust to seek operations without losing buffered data, as the mapping relationships are already established and can be rapidly applied when time reference changes occur.
Solution Approach 2:
The patent introduces an intermediary time reference mechanism that decouples the direct relationship between local time and reference time. This intermediary layer allows time adjustments during seek operations without directly invalidating the buffered media data's time references, enabling random access while preserving data integrity through the mediating time reference structure.
2Stability of the object's composition
If media data is buffered to handle constant bit rate from network/storage, then synchronization is maintained, but immediate processing is delayed and additional buffer management complexity is introduced
Solution Approach 1:
The system implements dynamic buffer management where the buffering behavior adapts based on the current operation mode. During regular playback, data is buffered for synchronization stability. During seek or trick-play operations, the buffer management dynamically adjusts to allow immediate processing of relevant data segments, reducing unnecessary delays while maintaining synchronization where required.
Solution Approach 2:
The media data buffer is segmented into multiple regions or segments with different management policies. Some segments are optimized for synchronization (buffered with time reference validation), while other segments are optimized for immediate processing. This segmentation allows the system to simultaneously maintain synchronization stability for critical data while enabling fast access for other data, reducing overall processing delay.
3Stability of the object's composition
If buffered media data is dropped or flushed during time reference changes, then synchronization is maintained, but data loss occurs and playback continuity is disrupted
Solution Approach 1:
The system implements feedback mechanisms that continuously monitor the relationship between presentation timestamps and display timestamps. When a time reference change is detected, the feedback system identifies which buffered data segments remain valid and which need adjustment, allowing selective processing rather than blanket dropping of buffered data. This feedback-driven approach maintains synchronization while preserving valid media data.
Solution Approach 2:
Instead of dropping buffered data when time references change, the system changes the time reference parameters themselves to accommodate the new state. By adjusting the timestamp parameters and recalculating the mapping relationships, the system maintains the buffered data's validity under the new time reference framework, avoiding data loss while preserving synchronization through parameter transformation rather than data elimination.
Data Source
AI summary
A method and device for synchronization and rate control of media data comprising adaptively computing an offset time using the reference time of a server, a local time of a client, and an associated time for presentation of the data, stamping the offset time on the media data, receiving the offset time stamped media data into a first buffer, processing the offset time stamped media data, computing an altered offset time, including the altered offset time with the processed media data, storing the processed media data in a second buffer, and selectively supplying the processed media data to a presentation sink unit according to the altered offset time, the server reference time, and the associated time of the media data.