Audio Decoder Special Frames for Instant Start and Codec Switching
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Solution Overview
Problem
Existing audio encoding and decoding technologies face challenges in seamlessly switching between different codec configurations, leading to potential glitches and reduced audio quality due to decoder start-up delays and incompatible codec configurations, especially in environments with variable bitrates.
Innovation Solution
Incorporating a special frame with additional information, such as pre-roll frames encoded using the same codec configuration, to facilitate immediate initialization and decoding of audio data, allowing seamless switching between codec configurations by providing necessary codec configuration details and pre-roll frames within the audio bitstream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If traditional audio decoding is used without pre-roll frames, then the decoder structure remains simple, but the decoder cannot initialize immediately and produces start-up delays
Solution Approach 1:
The patent applies preliminary action by including pre-roll frames at the beginning of the bit stream that contain encoded audio sample values from frames preceding the first frame. These pre-roll frames are decoded before the actual first frame to initialize the decoder's internal state (such as filter states and buffer contents) in advance, eliminating start-up delays and enabling immediate playback without waiting for subsequent frames to arrive.
2Adaptability or versatility
If codec configuration changes are made dynamically, then adaptability to variable bitrate environments is improved, but switching between configurations causes glitches and audio quality degradation
Solution Approach 1:
The patent applies preliminary action by including configuration change information in the pre-roll frames before the actual codec configuration switch occurs. This allows the decoder to prepare for and smoothly transition between different codec configurations without abrupt changes that would cause audible glitches or quality degradation.
Solution Approach 2:
The patent uses pre-roll frames as an intermediary mechanism between different codec configurations. These frames serve as a buffer zone that mediates the transition, allowing the decoder to gradually adapt from one configuration to another while maintaining audio quality continuity and avoiding direct abrupt switches that would cause glitches.
3Productivity
If pre-roll frames are included in the bit stream, then immediate playback is enabled, but the bit stream size increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the number of pre-roll frames based on the specific codec configuration and playback requirements. Different codec configurations may require different numbers of pre-roll frames (e.g., 1, 2, or 3 frames), allowing optimization between immediate playback capability and bit stream size based on the actual application needs.
Data Source
AI summary
An audio decoder decodes a bit stream of encoded audio data, which bit stream represents a sequence of audio sample values and includes a plurality of frames, wherein each frame includes associated encoded audio sample values. The audio decoder includes a determiner configured to determine whether a frame of the encoded audio data is a special frame including encoded audio sample values associated with the special frame and additional information, wherein the additional information include encoded audio sample values of a number of frames preceding the special frame, wherein the encoded audio sample values of the preceding frames are encoded using the same codec configuration as the special frame, wherein the number of preceding frames is sufficient to initialize the decoder to be in a position to decode the audio sample values associated with the special frame if the special frame is the first frame upon start-up of the decoder.