diff options
author | Vinod Koul <vinod.koul@intel.com> | 2016-07-11 06:13:29 -0400 |
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committer | Takashi Iwai <tiwai@suse.de> | 2016-07-11 06:45:39 -0400 |
commit | a5d48be457273e4faf34a2033c63f8890f3f9c6c (patch) | |
tree | d46f9c675d80c3306d86a7c919f3808794a23c36 /Documentation/sound/alsa | |
parent | 860c1994a70a0d2ab6f87fb7e72e722a8fb2c64c (diff) |
ALSA - hda: Fix timestamping documentation
Some typos in the documentation, so fix them up.
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/sound/alsa')
-rw-r--r-- | Documentation/sound/alsa/timestamping.txt | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/Documentation/sound/alsa/timestamping.txt b/Documentation/sound/alsa/timestamping.txt index 1b6473f393a8..9d579aefbffd 100644 --- a/Documentation/sound/alsa/timestamping.txt +++ b/Documentation/sound/alsa/timestamping.txt | |||
@@ -14,7 +14,7 @@ provides a refined estimate with a delay. | |||
14 | event or application query. | 14 | event or application query. |
15 | The difference (tstamp - trigger_tstamp) defines the elapsed time. | 15 | The difference (tstamp - trigger_tstamp) defines the elapsed time. |
16 | 16 | ||
17 | The ALSA API provides reports two basic pieces of information, avail | 17 | The ALSA API provides two basic pieces of information, avail |
18 | and delay, which combined with the trigger and current system | 18 | and delay, which combined with the trigger and current system |
19 | timestamps allow for applications to keep track of the 'fullness' of | 19 | timestamps allow for applications to keep track of the 'fullness' of |
20 | the ring buffer and the amount of queued samples. | 20 | the ring buffer and the amount of queued samples. |
@@ -53,21 +53,21 @@ case): | |||
53 | The analog time is taken at the last stage of the playback, as close | 53 | The analog time is taken at the last stage of the playback, as close |
54 | as possible to the actual transducer | 54 | as possible to the actual transducer |
55 | 55 | ||
56 | The link time is taken at the output of the SOC/chipset as the samples | 56 | The link time is taken at the output of the SoC/chipset as the samples |
57 | are pushed on a link. The link time can be directly measured if | 57 | are pushed on a link. The link time can be directly measured if |
58 | supported in hardware by sample counters or wallclocks (e.g. with | 58 | supported in hardware by sample counters or wallclocks (e.g. with |
59 | HDAudio 24MHz or PTP clock for networked solutions) or indirectly | 59 | HDAudio 24MHz or PTP clock for networked solutions) or indirectly |
60 | estimated (e.g. with the frame counter in USB). | 60 | estimated (e.g. with the frame counter in USB). |
61 | 61 | ||
62 | The DMA time is measured using counters - typically the least reliable | 62 | The DMA time is measured using counters - typically the least reliable |
63 | of all measurements due to the bursty natured of DMA transfers. | 63 | of all measurements due to the bursty nature of DMA transfers. |
64 | 64 | ||
65 | The app time corresponds to the time tracked by an application after | 65 | The app time corresponds to the time tracked by an application after |
66 | writing in the ring buffer. | 66 | writing in the ring buffer. |
67 | 67 | ||
68 | The application can query what the hardware supports, define which | 68 | The application can query the hardware capabilities, define which |
69 | audio time it wants reported by selecting the relevant settings in | 69 | audio time it wants reported by selecting the relevant settings in |
70 | audio_tstamp_config fields, get an estimate of the timestamp | 70 | audio_tstamp_config fields, thus get an estimate of the timestamp |
71 | accuracy. It can also request the delay-to-analog be included in the | 71 | accuracy. It can also request the delay-to-analog be included in the |
72 | measurement. Direct access to the link time is very interesting on | 72 | measurement. Direct access to the link time is very interesting on |
73 | platforms that provide an embedded DSP; measuring directly the link | 73 | platforms that provide an embedded DSP; measuring directly the link |
@@ -169,7 +169,7 @@ playback: systime: 938107562 nsec, audio time 938112708 nsec, systime delta -51 | |||
169 | Example 1 shows that the timestamp at the DMA level is close to 1ms | 169 | Example 1 shows that the timestamp at the DMA level is close to 1ms |
170 | ahead of the actual playback time (as a side time this sort of | 170 | ahead of the actual playback time (as a side time this sort of |
171 | measurement can help define rewind safeguards). Compensating for the | 171 | measurement can help define rewind safeguards). Compensating for the |
172 | DMA-link delay in example 2 helps remove the hardware buffering abut | 172 | DMA-link delay in example 2 helps remove the hardware buffering but |
173 | the information is still very jittery, with up to one sample of | 173 | the information is still very jittery, with up to one sample of |
174 | error. In example 3 where the timestamps are measured with the link | 174 | error. In example 3 where the timestamps are measured with the link |
175 | wallclock, the timestamps show a monotonic behavior and a lower | 175 | wallclock, the timestamps show a monotonic behavior and a lower |