Systems and methods for implementing efficient cross-fading between compressed audio streams

Patent metadata

Field	Value
Publication number	US-9779736-B2
Application number	US-201314395183-A
Country	US
Kind code	B2
Filing date	Apr 17, 2013
Priority date	Nov 18, 2011
Publication date	Oct 3, 2017
Grant date	Oct 3, 2017

Abstract

Systems and methods are presented for efficient cross-fading (or other multiple clip processing) of compressed domain information streams on a user or client device, such as a telephone, tablet, computer or MP3 player, or any consumer device with audio playback. Exemplary implementation systems may provide cross-fade between AAC/Enhanced AAC Plus (EAACPIus) information streams or between MP3 information streams or even between information streams of unmatched formats (e.g. AAC to MP3 or MP3 to AAC). Furthermore, these systems are distinguished by the fact that cross-fade is directly applied to the compressed bitstreams so that a single decode operation may be performed on the resulting bitstream. Moreover, using the described methods, similar cross fade in the compressed domain between information streams utilizing other formats of compression, such as, for example, MP2, AC-3, PAC, etc. can also be advantageously implemented. Thus, in exemplary embodiments of the present invention a set of frames from each input stream associated with the time interval in which a cross fade is decoded, and combined and recoded with a cross fade or other effect now in the compressed bitstream. Once sent through the client device's decoder, the user hears the transitional effect. The only input data that is decoded and processed is that associated with the portion of each stream used in the crossfade, blend or other interstitial, and thus the vast majority of the input streams are left compressed.

First claim

What is claimed:

1. A computer-implemented method for implementing efficient cross-fading between compressed audio streams, comprising:
obtaining parameters for a cross-fade between N audio streams comprising compressed packets;
time aligning the packets from each stream that are involved in the cross-fade;
synthesizing composite compressed packets containing information derived from the N streams; and
presenting the composite compressed packets to an audio decoder during a cross-fade phase.

2. The method of claim 1 , wherein at least one of:
(i) said time aligning is performed by operating upon data in a frame header of the stream, or
(ii) said time aligning is performed by operating upon data in a frame header of the stream and wherein each stream is encoded with EAAC Plus, and said data includes one or more of:
sampling_frequency_index, frame_length, adts_buffer_fullness, and number_of_raw_data_blocks_in_frame.

3. The method of claim 1 , wherein the synthesizing includes decomposing the data from each stream into its components, and separately combining each group of respective components.

4. The method of claim 3 , wherein the separately combining results in composite subcomponent packets, and wherein the method further comprises combining the composite subcomponent packets to produce a full composite bitstream packet.

5. The method of claim 1 , wherein the synthesizing includes decomposing data in each frame of each time aligned packet into its subcomponents, and wherein the subcomponents are encoded using different encoding methods.

6. The method of claim 5 , wherein the decomposing includes partially demultiplexing the data into the subcomponents.

7. The method of claim 1 , wherein the time aligning includes identifying a first frame from one of the streams based at least in part on sampling frequency and number of raw data blocks per frame for that stream.

8. A computer-implemented method for implementing efficient cross-fading between compressed audio streams, comprising:
obtaining parameters for a cross-fade between N audio streams comprising compressed packets;
time aligning the packets from each stream that are involved in the cross-fade;
synthesizing composite compressed packets containing information derived from the N streams; and
presenting the composite compressed packets to an audio decoder during a cross-fade phase, wherein N=2, and said presenting compressed packets to an audio decoder includes multiplexing each of the streams and the synthesized composite compressed packets according to a time index, as follows:
Fort less than or equal to T 1 , Stream 1;
Fort greater than T 1 but less than or equal to T 2 , synthesized composite compressed packets; and
For t greater than T 2 , Stream 2.

9. A computer-implemented method for implementing efficient cross-fading between compressed audio streams, comprising:
obtaining parameters for a cross-fade between N audio streams comprising compressed packets;
time aligning the packets from each stream that are involved in the cross-fade;
synthesizing composite compressed packets containing information derived from the N streams; and
presenting the composite compressed packets to an audio decoder during a cross-fade phase, wherein each stream is encoded with Enhanced Advanced Audio Coding (“EAAC”) Plus, and said time aligning the packets is performed by estimating the time instance for an (i+1) th frame in the stream as:
t ( i+ 1)=( i* 2048*number_of_raw_data_blocks_in_frame)/sampling_frequency.

10. A computer-implemented method for implementing efficient cross-fading between compressed audio streams, comprising:
obtaining parameters for a cross-fade between N audio streams comprising compressed packets;
time aligning the packets from each stream that are involved in the cross-fade;
synthesizing composite compressed packets containing information derived from the N streams; and
presenting the composite compressed packets to an audio decoder during a cross-fade phase, wherein each stream is encoded with EAAC Plus, and said time aligning the packets is performed by estimating the time instance for an (i+1) th frame in the stream by keeping a cumulative estimate of the total number of raw data blocks till the i th frame as follows:

total_number
⁢
_of
⁢
_raw
⁢
_data
⁢
_blocks
⁢
_in
⁢

_frame
i

=

∑

k
=
1

k
=
i

⁢

⁢

number_of
⁢
_raw
⁢
_data
⁢
_blocks
⁢
_in
⁢

_frame
k

and estimating:

t
⁡

(

i
+
1

)

′

=

(

2048
*
total_number
⁢
_of
⁢
_raw
⁢
_data
⁢
_blocks
⁢
_in
⁢

_frame
i

)

sampling_frequency

.

11. A computer-implemented method for implementing efficient cross-fading between compressed audio streams, comprising:
obtaining parameters for a cross-fade between N audio streams comprising compressed packets;
time aligning the packets from each stream that are involved in the cross-fade;
synthesizing composite compressed packets containing information derived from the N streams; and
presenting the composite compressed packets to an audio decoder during a cross-fade phase, wherein the synthesizing includes decomposing the data from each stream into its components, and separately combining each group of respective components, wherein N=2, wherein each stream is encoded with EAAC Plus, wherein packet pairs P(1,i) and P(2,j) can be both partially demultiplexed to identify three subcomponents, AAC Core, SBR, and PS, and wherein at least one of:
(i) the respective subcomponents are combined to generate composite subcomponents

Assignees

• Sirius Xm Radio Inc

Inventors

• Lowe Raymond
• Kalman Mark
• Sinha Deepen
• Ward Christopher

Classifications

• H04H60/04 Primary

  Studio equipment; Interconnection of studios · CPC title

• H04H20/38

  Arrangements for distribution where lower stations, e.g. receivers, interact with the broadcast · CPC title

• G10L19/00 Primary

  Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis (in musical instruments G10H) · CPC title

• G11B27/038

  Cross-faders therefor · CPC title

• G11B27/031

  Electronic editing of digitised analogue information signals, e.g. audio or video signals · CPC title