Audio Clock Generation via Video Signal Frequency Division
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Solution Overview
Problem
Current digital data transmission systems require separate cables for video and audio data, leading to complex connections and lower picture quality when multiplexing using IEEE1394, and suffer from increased cost and clock jitter issues when transmitting audio data with video data.
Innovation Solution
A data transmitter that frequency divides the audio clock using a predetermined parameter N and adds a count value CTS to the audio data, allowing simultaneous transmission of video and audio data over a single cable, reducing synchronization pull-in time and clock jitter by generating an audio clock on the receiving end.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate cables are used for video and audio data transmission, then transmission quality is maintained, but connection complexity increases
Solution Approach 1:
The patent merges video data and audio data into a single transmission cable by multiplexing them together. The audio data is superimposed on the video data transmission channel, allowing both types of data to be transmitted simultaneously through one cable, thereby reducing connection complexity while maintaining transmission quality.
Solution Approach 2:
The existing video transmission interface is made universal by enabling it to carry both video data and audio data. The interface maintains its original video transmission functionality while adding audio transmission capability through superposition, eliminating the need for separate audio cables.
2Device complexity
If IEEE1394 bus line is used to multiplex video and audio data, then single cable transmission is achieved, but picture quality deteriorates
Solution Approach 1:
The patent changes the parameter of data superposition by placing audio data in the horizontal blanking interval of video signals. This temporal parameter change allows audio data to be transmitted without interfering with the video data transmission timing, thereby maintaining picture quality while achieving single cable transmission.
3Adaptability or versatility
If IEEE1394 method is used for data transmission, then multiplexing is achieved, but processing complexity and cost increase
Solution Approach 1:
The patent employs self-service by utilizing the existing video transmission interface and its inherent horizontal blanking interval to carry audio data. The system leverages the existing infrastructure rather than requiring complex new processing circuits, thereby achieving multiplexing with minimal additional complexity.
4Reliability
If audio clock is transmitted through high-speed signal line, then synchronization is maintained, but jitter increases
Solution Approach 1:
The patent introduces an intermediary approach by deriving the audio clock from the video clock through frequency division. Instead of directly transmitting the audio clock through high-speed lines, the system uses the video clock as an intermediary reference, dividing it down to the required audio frequency. This eliminates the need for high-speed audio clock transmission and reduces jitter.
Data Source
AI summary
As shown in FIG. 7, a data receiver receives video data and audio data together with a frequency division parameter N that depends on the pixel clock of the video data and the sampling frequency of the audio data, and a count value CTS that is obtained by counting the period of the audio clock that has been subjected to frequency division by the frequency division parameter N, with the pixel clock, which are transmitted from a data transmitter, and subjects the pixel clock to frequency division by the count value CTS, phase-control the divided clock (s501) in accordance with a phase comparison clock (s505) that is obtained by dividing an audio clock (s403) oscillated from a VCO (504) by the frequency division parameter N, thereby generating an audio clock (s403).Accordingly, the data transmitter and the data receiver can satisfactorily implement multiplexing of audio data and video data, and transmission of the multiplexed data using an existing DVI cable, with a simple structure.