Audio Video Synchronization via Timestamp Compensation

Solution Overview

Problem

Existing methods for recording and synchronizing audio and video signals using mobile devices face challenges with unpredictable time delays in wireless data transfer protocols, leading to desynchronization issues, especially when using external microphones with smartphones, where ambient noise and variable waiting times for channel access result in audio signals being time-shifted relative to video signals.

Innovation Solution

A system and method involving a microphone unit and a video unit with synchronized system clocks, where time stamps are stored with recorded signals, and alignment is achieved through a data transfer protocol that coordinates access to the transmission channel, allowing for subsequent synchronization of audio and video signals by calculating and adjusting time values, and optionally resampling the audio signal to match the video signal's duration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If wireless data transfer protocols (WLAN, Bluetooth, Wi-Fi) are used to transmit audio signals from external microphones to camera units, then wireless transmission and mobility are achieved, but unpredictable time delays occur due to coordinated channel access and bidirectional acknowledgment mechanisms

Engineering Contradiction:

Improvewireless transmission capabilityVSAvoidunpredictable time delay

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent applies preliminary action by recording time stamps at the moment of audio signal capture in the external microphone and video signal capture in the camera unit, before any wireless transmission occurs. These time stamps serve as reference markers that allow subsequent synchronization of the audio and video signals even after unpredictable delays occur during wireless transmission. The time stamps are embedded in the data packets transmitted via wireless protocols, enabling the receiving device to calculate and compensate for transmission delays.

Inventive Principle:

Principle #10Preliminary action

2Reliability

If wired connection is used to connect external microphone to camera unit, then synchronous audio and video recording is achieved, but mobility and practicality in situations like auditoriums are reduced

Engineering Contradiction:

Improvesynchronization accuracyVSAvoidmobility and practicality

Core Design Contradiction:

ReliabilityVSEase of operation

Solution Approach 1:

The patent replaces the mechanical wired connection system with a wireless data transmission system. Instead of using physical cables to connect the external microphone to the camera unit, the invention utilizes wireless communication protocols (WLAN, Bluetooth, Wi-Fi) to transmit audio data packets. This substitution maintains the functional requirement of data transmission while eliminating the physical constraint of wired connections, enabling mobility and practical use in situations like auditoriums where wired connections would be cumbersome or impossible.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If bidirectional data transfer with acknowledgment is used, then reliable data transmission is achieved, but additional unpredictable delays are introduced

Engineering Contradiction:

Improvedata transmission reliabilityVSAvoidacknowledgment delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent applies preliminary action by recording time stamps at the moment of audio signal capture in the external microphone and video signal capture in the camera unit, before any wireless transmission occurs. These time stamps serve as reference markers that allow subsequent synchronization of the audio and video signals even after unpredictable delays occur during wireless transmission. The time stamps are embedded in the data packets transmitted via wireless protocols, enabling the receiving device to calculate and compensate for transmission delays.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS11551725B2Method and system for recording and synchronizing audio and video signals and audio and video recording and synchronization system

Publication Date: 2023.01.10 SENNHEISER ELECTRONICS GMBH & CO KG

AI summary

There is set forth a method and a system for recording and synchronizing audio and video signals. The audio signal and the video signal are stored together with time stamps from a respective associated system clock. The invention relates to an adaptation of the duration of the recorded audio sequence to the duration of an associated video sequence in order to level out differences in synchronization of the two system clocks. Alignment of the two system clocks is also introduced, which is based on a data transfer which has variable waiting times for the access to a transmission channel. This thus permits clock alignment with means as are available for example on a smartphone.