Lines Matching +full:codec +full:- +full:driver
1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
4 <meta http-equiv="content-type" content="text/html;charset=iso-8859-1">
13 <!-- #BeginDate format:En2m -->15-Nov-2012 06:42<!-- #EndDate -->
19 Driver ID: <tt>WWV_AUDIO</tt><br>
20 Autotune Port: <tt>/dev/icom</tt>; 1200/9600 baud, 8-bits, no parity<br>
23 …driver synchronizes the computer time using shortwave radio transmissions from NIST time/frequency…
24 …driver requires an audio codec or sound card with sampling rate 8 kHz and μ-law companding to d…
25 …driver is accurate within 1 ms relative to the broadcast time when tracking a station. However, va…
26 …-GHz P4 running FreeBSD 6.1 is generally within 0.1 ms short-term with 0.4 ms jitter. The long-ter…
27 <p>The driver performs a number of error checks to protect against overdriven or underdriven input …
28 …driver incorporates several features in common with other audio drivers such as described in the <…
30 …driver processes 8-kHz μ-law companded codec samples using maximum-likelihood techniques which …
31 …driver are based on a machine language program developed for the TAPR DSP93 DSP unit, which uses t…
34 …-Hz pulses and 100-Hz subcarrier are first separated using a 600-Hz bandpass filter centered on 11…
35 …-Hz subcarrier relative to the second pulse is fixed at the transmitter; however, the audio stage …
36 …-width discriminator. The discriminator samples the I channel at 15 ms (<i>n</i>), 200 ms (<i>s</…
37 …-static miscellaneous bits, such as DST indicator, leap second warning and DUT1 correction. In thi…
38 <h4>Maximum-Likelihood Decoder</h4>
39 …ssociated with the maximum over all averaged values then becomes the maximum-likelihood candidate …
40 …-likelihood digit, likelihood vector and other related data. The maximum-likelihood digit for each…
41 …-likelihood digit. If a digit likelihood exceeds the decision level and compares with previous dig…
43 …codec clock. Its frequency is disciplined by a frequency-lock loop (FLL) which operates independen…
44 …ncy averaging interval is 8 seconds, in order to compensate for intrinsic codec clock frequency of…
45 …r, the data decoding functions are driven by the epoch. The decoder is phase-locked to the epoch i…
46 … after a long fade. Therefore, a candidate is considered valid only if the 5-ms signal amplitude a…
49 …d noise alone. The driver very aggressively soaks up every scrap of signal information, but has to…
52 …gation conditions. The performance of the NTP daemon disciplined by this driver is clearly better …
55 <p>The figure was constructed using a 2.4-GHz P4 running FreeBSD 6.1. For these measurements the co…
56 …the receiver at Newark, DE, varies over 9.0-9.3 ms. In addition, the receiver contributes 4.7 ms a…
58 …driver begins operation immediately upon startup. It first searches for one or both of the station…
59 …driver acquires second synch, which can take up to several minutes, depending on signal quality. W…
61 … WWV and WWVH signals may appear alone, together or not at all. When the driver has mitigated whic…
63 …iods the root distance increases at 15 μs per second, which makes the driver appear less likely…
65 …driver includes provisions to automatically tune the radio in response to changing radio propagati…
66 …driver will attempt to open the device <tt>/dev/icom</tt> and, if successful will activate the aut…
67 …driver operates as described above to set the clock. However, during seconds 59, 0 and 1 of each m…
71 … when the ray path is in moonlight (0100-1300 UTC) and the higher frequencies when the path is in …
73 …driver status is using the <tt>ntpq</tt> program and the <tt>clockvar</tt> command. This displays …
78 … <tt>WH</tt> for WWVH) and frequency (2, 5, 10, 15 or 20), <tt>score</tt> 32-bit shift register re…
79 <pre><tt>wwv5 000d 111 5753 3967/20.1 3523/10.2 WV20 bdeff 100 8348/30.0 WH20 0000 1 22/-12.4</tt><…
85 …re decoded from the received data and are in fixed-length format. The remaining fields are in vari…
90 …<dd>The quality character is a four-bit hexadecimal code showing which alarms have been raised. Ea…
99 …<dd>Compare alarm. A maximum-likelihood digit failed to agree with the current associated clock di…
103 …<dd>The timecode format itself is self explanatory. Since the driver latches the on-time epoch dir…
111 …k is set, the interval since last set is the number of minutes since the driver was started; after…
113 …<dd>The audio gain shows the current codec gain setting in the range 0 to 255. Ordinarily, the rec…
121 …<dd>The frequency offset is the current estimate of the codec frequency offset to within 0.1 PPM. …
123 …s of two to a maximum of 1024 s. Attainment of the maximum indicates the driver is operating at th…
127 …k was set on the last minute, the AGC is safely in the middle ot the range 0-255, and the receiver…
135 <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0.</dd>
137 …<dd>Ordinarily, this field specifies the driver reference identifier; however, the driver sets the…
139 <dd>Not used by this driver.</dd>
141 …<dd>Specifies the microphone port if set to zero or the line-in port if set to one. It does not se…
143 …e input signal. For this purpose, the speaker volume must be set before the driver is started.</dd>