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Read the white paper carefully..

213.84.55.132

Posted by Frank.. on November 4, 2004 at 13:34:50

In Reply to: Re: Depends... posted by Christine Tham on November 4, 2004 at 12:41:02:

It states clearly how during the encoding process a difference data stream from the original 24/96 data stream is created by comparing it with the upsampled version from the downsampled core data.

>>>
"The generalized concept of core+extension coding is illustrated in Figure 1. To encode 96 kHz LPCM the input audio stream is fed to a 96 to-48kHz down sampler and the resulting 48kHz signal is encoded using standard core encoder as in Figure 1 A). In the core+extension coding scheme that we first introduced in (4):

• The core data is fed to a local core decoder whose output is up sampled in a 48-to-96kHz interpolator resulting in an interpolated core LPCM audio, denoted as signal “2” in Figure 1 A). Both operations are performed in the “Reconstruct Core Audio Components” block.

• In the “Generate Residuals” block the interpolated core audio is subtracted from the delayed version of input 96kHz LPCM audio (signal “1”) to generate the LPCM residual (signal “3”). The “Preprocess Input Audio” block performs the delay operation.

• The extension encoder (“Generate Extension Data” block) processes the residual LPCM signal and outputs the extension data. This data, along with the core data, is assembled in a packer to produce a core+extension bit stream.
<<<

Above is describing encoder operation.

It's a bit like the following

Original data:
10 12 14 16 14 12 10 8

After filtering and downsampling you get core data:
11 15 13 9

Upsampling algo gives :
11 12 15 14 13 11 9 8

Subtract from original gets extension data:
+1 0 +1 -2 -1 +1 -1 0

Pack core data + extension data into dts stream

Decoding is fairly easy.
Standard DTS decodeer just decodes the core data.

DTS9624 decoder decodes the core data. Interpolates it with the same algo as used in the encoder and adds the extension data.

It's an elegant solution.
The 48kHz core data is a decent downsampled audio signal.
The 96kHz reconstruction is augmented by the additional extension data requiring a lower bitrate. Difference data generally requires far fewer bits to encode.

Frank

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