Audio Decoder Special Frames for Instant Codec Reconfiguration
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Solution Overview
Problem
Existing audio encoding and decoding technologies face challenges in seamlessly switching between different codec configurations, leading to decoder start-up delays and potential glitches during bitrate changes in variable transmission channels.
Innovation Solution
Incorporating a special frame with additional information encoding previous frames' audio sample values, allowing immediate initialization and decoding of audio data, even when switching between different codec configurations, by including pre-roll frames that match the codec configuration of the special frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a decoder is initialized normally without pre-roll frames, then the decoder structure is simple, but the decoder experiences start-up delays when switching between codec configurations
Solution Approach 1:
The patent applies preliminary action by inserting pre-roll frames at the beginning of audio segments before the actual audio content. These pre-roll frames contain encoded audio data that allows the decoder to initialize its internal state (such as filter banks, buffer, and configuration parameters) before the main audio playback begins. This ensures that when the decoder encounters a frame requiring initialization, it is already in the correct state, eliminating start-up delays and audible glitches during codec configuration switching.
2Loss of time
If pre-roll frames are added to enable immediate playback, then playback continuity is improved, but the bit stream size increases
Solution Approach 1:
The patent applies partial action by adding only the minimum necessary number of pre-roll frames (typically one frame) to enable decoder initialization, rather than adding excessive frames. The pre-roll frames contain only the essential encoded audio data required for decoder state initialization, not the entire audio segment. This minimizes the additional bit stream size while achieving the goal of eliminating start-up delays.
3Adaptability or versatility
If the decoder switches between different codec configurations, then adaptability to varying network conditions is improved, but audio glitches may occur during switching
Solution Approach 1:
The patent uses preliminary action by placing pre-roll frames at segment boundaries where codec configuration changes occur. These pre-roll frames are encoded with the target codec configuration parameters, allowing the decoder to switch configurations smoothly without audio glitches. The pre-roll frames prepare the decoder state in advance for the upcoming configuration change, ensuring continuous and glitch-free audio playback during adaptive bitrate switching.
Solution Approach 2:
The pre-roll frames act as an intermediary between different codec configurations. When switching from one codec configuration to another, the pre-roll frames provide a transition buffer that mediates the configuration change. The decoder processes these intermediary frames to gradually adapt to the new configuration parameters, preventing abrupt changes that would cause audio glitches while maintaining adaptability to varying network conditions.
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.