Aplay resampler #750
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Aplay resampler #750
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Do not allow audio frames to accumulate in the FIFO, and do not block when writing to the ALSA PCM. By this means we prevent the delay from increasing much beyond our chosen buffer sizes, and ensure that if it becomes necessary to drop audio frames then we always drop only the oldest ones. Avoid underruns on the ALSA PCM as far as possible by inserting silence when there are not enough frames available to maintain the ALSA buffer fill level above the period size. Use the BlueALSA PCM "running" property to detect when the transport becomes idle. This avoids closing the ALSA PCM whenever an unstable Bluetooth link causes a short break in the stream, allowing **bluealsa-aplay** to play silence to keep the ALSA stream running. When the transport becomes idle, drain the ALSA PCM before closing it to ensure that all audio frames are played out.
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #750 +/- ##
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+ Coverage 70.39% 70.55% +0.16%
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Files 96 99 +3
Lines 16103 16230 +127
Branches 2520 2535 +15
==========================================
+ Hits 11335 11451 +116
- Misses 4649 4660 +11
Partials 119 119 ☔ View full report in Codecov by Sentry. |
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I'm currently in the review process. If you agree, I will push the refactoring bits to the master branch and keep only the resampling-related changes here. Please give me a day or two to examine the refactoring, then I will look at the resampler. Thank you very very much for this piece of work! |
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This is my attempt to address the topics previously discussed in PR #459
The io_worker_routine() function is already quite complex and can be difficult to read, so before adding more complexity, the first three commits simply factor out some of the code into new files.
The commit "aplay: improve overrun/underrun handling" uses a different approach, but addresses the same problem, as #459 and therefore if merged it closes #459
The libsamplerate resampler causes high CPU usage. Its not so bad on x86_64, but really very high on armhf. I have not tried with arm64. Having said that, I have tested on an old pi zero W (32bit armv6) with the "SINC_FASTEST" converter and got very stable audio with accurate delay reporting watching a 4 hour video stream.
topshowed bluealsa-aplay consuming 28% of the (single core) CPU but the pi continued to run smoothly. So anyway this is left as an option and not included in the build by default.