DTS

• Codec ID: 0x2001
• Company: DTS Inc.

DTS Coherent Acoustics is a perceptual audio codec. The main technique used is a QMF filter together with Huffman, ADPCM and vector quantization.

Specification can be found through the ETSI (mirrored here), search for DTS. Info completing the incomplete specification can be found here: http://webapp.etsi.org/action%5CPU/20021224/ts_102114v010201p.pdf, http://gauss.ffii.org/PatentView/EP864146, and http://ofi.epoline.org/view/GetDossier?dosnum=&pubnum=EP864146&lang=EN# .

The VideoLAN project has created libdts/libdca an open source implementation of DTS. Unfortunately libdts was pushed underground through patent scare tactics for a while.

Bitstream coding

There are four different bitstream formats -- little- or big-endian and 16 or 14 bits per word.

Raw bitstream coding

Raw bitstream is packed into 16-bit words with possible little- or big-endian.

14-bit words

This kind of bitstream is packed into 16-bit words where high two bits contain some auxiliary information (parity?). This coding is used in many DTS-in-WAV files.

How to distinguish different versions

Every frame in DTS starts with 32-bit syncword which can be used to distinguish current bitstream encoding:

Sequence	Bitstream type
7F FE 80 01	raw big-endian
FE 7F 01 80	raw little-endian
1F FF E8 00 07 Fx	14-bit big-endian
FF 1F 00 E8 Fx 07	14-bit little-endian

Frame format

Size	Explanation	Value
32 bits	Sync marker	0x7FFE8001
1 bit	Frame type (or last frame)	0 - termination frame, 1 - normal frame
5 bits	Deficit sample count	number of samples in block - 1 (should be 31 for normal frame)
1 bit	CRC present
7 bits	Number of blocks	5-127
14 bits	Frame size in bytes - 1	95-16383
6 bits	Channel configuration	values 0-15 are standard, 16-63 are user-defined
4 bits	Sample frequency	See table below
5 bits	Bitrate
TODO