Image Data Compression Device Rate Control and Frame Skip
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Solution Overview
Problem
The MPEG-4 standard for image data compression faces challenges in achieving efficient rate control and reducing circuit size in portable devices, leading to increased CPU load and power consumption, while existing rate control methods result in block noise and inefficient data compression.
Innovation Solution
An image data compression device with a quantization section, FIFO buffer, encoded data generation, rate control, and frame skip sections, which calculates the quantization parameter based on average data size and performs asynchronous processing to maintain a constant bit rate and prevent block noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a series of encode processing is entirely performed by hardware, then compression efficiency is improved, but circuit scale increases making it difficult to reduce device size
Solution Approach 1:
The encode processing is divided into two segments: quantization processing performed by hardware (image data processing section) and encoded data generation performed by software (encoded data generation section). This segmentation allows the patent to achieve high compression efficiency through hardware acceleration while avoiding the need for complete hardware implementation, thus reducing circuit scale.
2Device complexity
If a series of encode processing is entirely performed by software, then device size is reduced, but CPU load increases limiting processing time and performance
Solution Approach 1:
The encode processing is segmented with quantization performed by hardware and encoded data generation by software. This division reduces CPU load compared to full software implementation while maintaining smaller device size, as only the software section is needed rather than a complete hardware encoder.
Solution Approach 2:
A FIFO buffer is introduced as an intermediary between the hardware quantization section and the software encoded data generation section. The buffer enables asynchronous operation, allowing the hardware to process data continuously while the software operates at its own pace, thus reducing CPU waiting time and improving overall processing efficiency.
3Stability of the object's composition
If rate control is performed using the MPEG-4 method, then constant rate is achieved, but block noise appears in decompressed images deteriorating display quality
Solution Approach 1:
The patent changes the rate control parameter from using a single frame's encoded data size to using the average encoded data size of N previous frames. This parameter change smooths out rate fluctuations and reduces the impact of block noise while maintaining relatively constant bit rate, as the average over multiple frames provides more stable rate control.
4Quantity of substance
If quantization parameter is increased to control data size, then bit rate is reduced, but display quality deteriorates due to block noise
Solution Approach 1:
The patent performs preliminary action by buffering quantized data for at least N frames in the FIFO buffer before encoded data generation. This allows the system to accumulate data from multiple frames and use average data size calculation, which smooths out the impact of aggressive quantization and maintains better display quality while still controlling overall data size.
Data Source
AI summary
An image data compression device includes: a quantization section which quantizes image data based on a quantization parameter; a FIFO buffer section in which quantized data for at least N frames (N is an integer larger than one) is buffered; an encoded data generation section which reads the quantized data from the FIFO buffer section, and generates encoded data; a rate control section which changes a quantization step by using a data size of the encoded data; and a frame skip section which skips a quantization processing of the quantization section. The rate control section calculates the quantization parameter by using an average data size of the encoded data for previous N frames, and the frame skip section performs the skip processing when a frame in which the quantization parameter is greater than a threshold continues equal to or more than a number of times for a number threshold.