MP4 Recording Apparatus Audio-Video Synchronization
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Solution Overview
Problem
The MP4 file format does not synchronize the sampling points for moving images and audio sounds, leading to unnatural reproduction when combining files, as the timing for moving image and audio data does not coincide, causing audio to be reproduced before or after the corresponding moving image.
Innovation Solution
A recording apparatus that codes moving image data and audio data separately based on distinct sampling periods, adjusts the recording start position of audio data to precede the moving image data, and ensures synchronized reproduction by managing offset information in the MP4 file format to align the reproduction timings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If moving image data and audio data are coded separately based on different sampling periods, then the coding efficiency and adaptability are improved, but the reproduction timing synchronization deteriorates
Solution Approach 1:
The patent applies preliminary action by recording audio data before moving image data in the file structure. Specifically, the audio data is positioned at an earlier offset in the file, and the reproduction control unit is pre-configured to read audio data first and then read moving image data subsequently. This preliminary arrangement of data positions and playback timing ensures that even though the data are coded at different sampling rates, their reproduction timings are synchronized, preventing audio from playing before or after the corresponding video frames.
2Manufacturing precision
If audio data recording start position is set to precede moving image data, then the reproduction timing synchronization is improved, but the file structure complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the audio-video data structure into distinct, independently manageable segments. The audio data and moving image data are stored as separate data blocks within the file, each with its own offset position and size metadata. This segmentation allows the reproduction control unit to independently manage the reading and playback timing of each data type, simplifying the overall file structure while ensuring proper synchronization through controlled access to each segment.
3Adaptability or versatility
If separate coding units are used for moving image and audio data, then the coding flexibility is improved, but the reproduction coordination complexity increases
Solution Approach 1:
The patent introduces an intermediary component - the reproduction control unit - that acts as a mediator between the separately coded audio and moving image data. This control unit coordinates the reproduction process by reading audio data and moving image data in a specific sequence based on their offset positions, and controlling their playback timing to ensure synchronization. The intermediary manages the complexity of coordinating separately coded data streams, allowing flexible coding while maintaining synchronized reproduction.
Data Source
AI summary
A recording apparatus codes moving image data on a unit basis of a moving image sample corresponding to a first period, codes the audio data on a unit basis of an audio sample corresponding to a second period, stores the coded moving image data and audio data in a moving image file and records the moving image data and the audio data in a recording medium, determines based on a recording start position of the obtained moving image data, a recording start position of the obtained audio data to be a position preceding the recording start position of the obtained moving image data by at least the audio sample corresponding to the second period, and determines a reproduction start position of the recorded audio data to be a position following a head of the recorded audio data by the unit of the audio data.