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Two indices into the fEntries ring buffer are used in TimeComputer, fLastEntry which points to the most recent sample and fFirstEntry which points to the oldest one. The drift calculation then uses the oldest values pointed at by fFirstEntry to produce smoother values. Both indices are initialized to 0, then fLastEntry is incremented prior to writing the first sample, resulting in the first sample to be written to fEntries[1]. When drift is calculated on subsequent samples, they were using the uninitialized data from fEntries[0] due to fFirstEntry still pointing there, until enough samples had been added for fFirstEntry to be moved forward. The resulting incorrect drift values would depend on the entry content and ratio between real and performance time and generally end up being much too small. The drift values are published on the time source and used to correct the conversion between performance and real time in BTimeSource::RealTimeFor(). Given the incorrectly small drift values, this conversion produced real time values far in the future, causing increased delays in processes that wait for such computed real times. One likely victim was the startup of the AudioMixer, as it generally starts soon after the driver and its MultiAudioNode. If it started right in the time window where the drift was broken, it would end up delaying its initial buffer processing by a factor generally depending on the difference between real and performance time start points, so usually the difference of the start of the boot process to the start of the audio driver. The symptom was then noticable by initial silence after boot, as the mixer was not producing any buffers until the wrongly calculated real time had been reached. After that, lots of queued up events were processed at once, resulting in a CPU spike and glitchy audio for a couple of seconds after which audio finally normalized. As the problem was in the MultiAudioNode all mutli audio drivers were affected, HDA being the most prominent. As the erroneous delay depended on the initial entry content and the boot time, it was highly variable. Whether or not the mixer was affected at all also depended on it starting reasonably early after the driver, which made the symptom of the bug appear and disappear depending on slight timing changes, making unrelated code changes look like they were affecting the bug. The fFirstEntry index is now updated to fLastEntry after the initial entry is added, so that the drift calculation always uses valid data. Fixes #16222, may also affect #15472 and possibly other "no audio" tickets in case they are really "delayed" audio tickets. Change-Id: I61f4a67e8b8bf14d2f311cb41b24a1c385aebc19 Reviewed-on: https://review.haiku-os.org/c/haiku/+/3092 Reviewed-by: waddlesplash <waddlesplash@gmail.com>
Haiku
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Haiku is an open-source operating system that specifically targets personal computing. Inspired by the BeOS, Haiku is fast, simple to use, easy to learn and yet very powerful.
Goals
- Sensible defaults with minimal configuration required.
- Clean, clear, concise code.
- Unified desktop environment.
Trying Haiku
Haiku provides pre-built nightly images and release images. Haiku is compatible with a large variety of hardware, but in case you don't want to "take the plunge" and install Haiku on bare metal, you can install it on a virtual machine (VM) instead. If you've never used a VM before, you can follow one of the "Emulating Haiku" guides.
Compiling Haiku
See ReadMe.Compiling.
Contributing
Haiku is a meritocratic open source project with a large variety of tasks. Even if you can't write code, you can still help! Haiku needs designers, (technical) writers, translators, testers... Get involved and help out!
Contributing code
If you're submitting a patch to us, please make sure you're following the patch submitting guidelines.
If you're having trouble finding something in the source tree, you can use one of our web-based source code browsers:
- https://xref.landonf.org/ (OpenGrok, provided by Landon Fuller)
- https://git.haiku-os.org/ (git, provided by Haiku, Inc.)
Contributing documentation
The main piece of documentation that still needs work are the API docs (found
in the tree at docs/user). Just find an undocumented class, write
documentation for it, and submit a patch.
Contributing translations
See wiki:i18n.
Contributing software ports
See HaikuPorts.
Contributing to our infrastructure
See Infrastructure.