7 DTX test sequences

06.543GPPTest sequences for the GSM Enhanced Full Rate (EFR)TS

This subclause describes the test sequences designed to exercise the VAD algorithm (GSM 06.82 [6]), comfort noise (GSM 06.62 [4]) and discontinuous transmission (GSM 06.81 [5]).

7.1 Codec configuration

The VAD, comfort noise and discontinuous transmission shall be tested in conjunction with the speech encoder (GSM 06.60 [2]). The speech encoder shall be configured to operate in the DTX mode defined in GSM 06.62 [4].

7.2 DTX test sequences

Each DTX test sequence consists of four files:

– files for input to the GSM enhanced full rate speech encoder: *.INP;

– files for comparison with the encoder output: *.COD;

– files for input to the GSM enhanced full rate speech decoder: *.DEC;

– files for comparison with the decoder output: *.OUT.

The *.DEC files are generated from the corresponding *.COD files.

In a correct implementation, the speech encoder parameters generated by the *.INP file shall be identical to those specified in the *.COD file; and the speech decoder output generated by the *.DEC file shall be identical to that specified in the *.OUT file.

Table 6 lists the DTX test sequences and their size in frames.

7.2.1 Predictor values computation

The computation of the predictor values described in GSM 06.82 [6] is not tested explicitly, since the results from the computation are tested many times via the spectral comparison and threshold adaptation tests.

7.2.2 Spectral comparison

The spectral comparison algorithm described in GSM 06.82 [6] is tested by the following test sequence:

– DTX01. *

7.2.3 Threshold adaptation

The threshold adaptation algorithm described in GSM 06.82 [6] is tested by the following test sequence:

– DTX02. *

7.2.4 Periodicity detection

The periodicity detection algorithm described in GSM 06.82 [6] is tested by the following test sequence:

– DTX03. *

7.2.5 Tone detection

The tone detection algorithm described in GSM 06.82 [6] is tested by the following test sequence:

– DTX04. *

7.2.6 Safety and initialisation

This sequence checks the safety paths used to prevent zero values being passed to the norm function. It checks the functions described in the adaptive filtering and energy computation, and the prediction values computation given in GSM 06.82 [6]. This sequence also checks the initialisation of thvad and the rvad array:

– DTX05. *

7.2.7 Comfort noise test sequence

The test sequences described in sub-subclauses 7.2.2 to 7.2.6 are designed to exercise the VAD described in GSM 06.82 [6] and the discontinuous transmission described in GSM 06.81 [5]. The following test sequence is defined to exercise the comfort noise algorithm described in GSM 06.62 [4]:

– DTX06.*

7.2.8 Real speech and tones

The test sequences cannot be guaranteed to find every possible error. There is therefore a small possibility that an incorrect implementation produces the correct output for the test sequences, but fails with real signals. Consequently, an extra sequence is included, which consists of very clean speech, barely detectable speech and a swept frequency tone:

– DTX07. *

NOTE: Some of the DTX test sequences contain homing frames. The DTX test sequences are therefore only suitable for testing a single transcoding.

Table 6: Location and size of DTX test sequences

size

(bytes)

Disk No.

File Name

No. of Frames

*.INP

*.COD

*.DEC

*.OUT

4/8

DTX01

710

227 200

349 320

350 740

227 200

4/8

DTX02

933

298 560

459 036

460 902

298 560

4/8

DTX03

156

49 920

76 752

77 064

49 920

4/8

DTX04

245

78 400

120 540

121 030

78 400

4/8

DTX05

56

17 920

27 552

27 664

17 920

4/8

DTX06

771

246 720

379 332

380 874

246 720

4/8

DTX07

1188

380 160

584 496

586 872

380 160