Immediate Playout Frames for Seamless Audio Codec Switching
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Solution Overview
Problem
MPEG-4 Audio lacks the capability to generate, transport, and process Immediate Playout Frames (IPFs) necessary for seamless audio decoding and playback, especially during codec configuration changes, leading to potential gaps or inaccuracies in audio output.
Innovation Solution
An audio decoder and encoder system that identifies and processes Immediate Playout Frames (IPFs) by including additional information from preceding frames, allowing seamless codec configuration switching and continuous audio output without gaps, using MPEG-4 Audio bitstream extensions like Data Stream Elements (DSE) or extension_payload elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a decoder switches to a different codec configuration (e.g., different bitrate), then the audio can adapt to different streaming requirements, but the decoder cannot guarantee correct output when decoding only the current access unit without preceding frames and configuration data
Solution Approach 1:
The patent embeds pre-roll frames (preceding audio frames) and configuration data directly within the current access unit before the actual audio data. This preliminary inclusion of necessary decoding information allows the decoder to initialize and produce correct output immediately upon receiving the access unit, without requiring external or preceding frames. The pre-roll frames are positioned at the beginning of the access unit to prepare the decoder state in advance.
Solution Approach 2:
The patent combines multiple elements that are typically separate into a single integrated access unit: configuration data (AudioSpecificConfig), pre-roll frames (preceding audio frames), and current audio frames are all merged into one access unit structure. This consolidation ensures that all necessary information for correct decoding is contained within a single transport unit, enabling reliable playback during codec configuration changes.
2Reliability
If the first access unit carries new configuration data and pre-roll frames to initialize the decoder, then correct audio output can be guaranteed, but the size of the access unit increases significantly
Solution Approach 1:
The patent segments the access unit into distinct functional parts with clear syntax markers: configuration data section, pre-roll frames section, and current audio frames section. Each segment is clearly delineated using MPEG-4 syntax elements, allowing the decoder to efficiently parse and process only the necessary portions. This structured segmentation organizes the large amount of data into manageable, purpose-specific sections.
3Productivity
If MPEG-4 Audio follows strict frame granularity for transport, then efficient data transmission is maintained, but the inability to include preceding frames within the current frame prevents immediate playout capability
Solution Approach 1:
The patent nests pre-roll frames and configuration data within the structure of the current access unit, creating a nested hierarchy where previous frames are embedded inside the current frame's data structure. This nesting allows the transport system to maintain frame granularity efficiency while enabling immediate playout capability, as the nested pre-roll frames are self-contained within the current access unit boundary.
Data Source
AI summary
Described herein is an audio decoder for decoding a bitstream of encoded audio data, wherein the bitstream of encoded audio data represents a sequence of audio sample values and comprises a plurality of frames, wherein each frame comprises associated encoded audio sample values, the audio decoder comprising: a determiner configured to determine whether a frame of the bitstream of encoded audio data is an immediate playout frame comprising encoded audio sample values associated with a current frame and additional information; and an initializer configured to initialize the decoder if the determiner determines that the frame is an immediate playout frame, wherein initializing the decoder comprises decoding the encoded audio sample values comprised by the additional information before decoding the encoded audio sample values associated with the current frame. Described are further a method for decoding said bitstream of encoded audio data as well as an audio encoder, a system of audio encoders and a method for generating said bitstream of encoded audio data with immediate playout frames. Described are moreover also an apparatus for generating immediate playout frames in a bitstream of encoded audio data or for removing immediate playout frames from a bitstream of encoded audio data and respective non-transitory digital storage media.