Indeo Audio

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Revision as of 10:53, 20 May 2012 Kostya (Talk | contribs) ← Previous diff		Current revision Kostya (Talk | contribs)
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	* Samples: http://samples.mplayerhq.hu/A-codecs/Indeo_audio/		* Samples: http://samples.mplayerhq.hu/A-codecs/Indeo_audio/
-	Related to the [[Intel Music Coder]] but with different codebooks and bitstream format.	+	This is the next version of [[Intel Music Coder]] with slightly different coding parameters
		+	(all algorithms are the same) and joint stereo mode.
	=== Header format ===		=== Header format ===
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	[[Category:Audio Codecs]]		[[Category:Audio Codecs]]
-	[[Category:Undiscovered Audio Codecs]]	+	[[Category:Incomplete Audio Codecs]]

---

Current revision

• Format: 0x402
• Company: Intel, now Ligos
• Samples: http://samples.mplayerhq.hu/A-codecs/Indeo_audio/

This is the next version of Intel Music Coder with slightly different coding parameters (all algorithms are the same) and joint stereo mode.

Header format

  bit  0   - should be zero
  bit  1   - should be zero
  bit  2   - stereo flag
  bits 3-8 - block size code
  bit  9   - codebook set selector (0 - no escapes, 1 - with escapes)
  bit 10   - codebook selector
  bit 11   - use raw coding
  
  bit 12   - SNR offset (-30 or -10)

Block size code:

  0, 34-50 - (block_size + 14) 16-bit words
  33       - 32 words
  1-32     - (block_size + 15) words
  51-63    - invalid value

Levels

There are 32 levels, coded with either one of codebooks or in raw form.

Decoding Huffman-coded levels is the same as in Intel Music Coder but with different tables.

Raw form:

  1st coefficient - 5 bits
  2nd coefficient - 7 bits
  others          - 4 bits per coefficient

Level reconstruction is also the same as in Intel Music Coder except for raw form.