It's currently possible to seek to the total sample count of an audio
loader. We must limit seeking to one less than that count.
This mistake was duplicated in both AudioCodecPluginSerenity/Ladybird,
so the computation was moved to a helper in the base AudioCodecPlugin.
When the default audio device changes on the host, it's convenient to
automatically switch to that device rather than needing to reload the
page to update.
We are currently forcing audio to play with a sample size of 16 bits. We
are also feeding the output audio device a hard-set amount of samples
without considering the actual size of its sample buffer. This would
cause a wide array of issues when playing audio elements. On my Linux
machine, we would hear some cracking; on my macOS machine, audio was
quite garbled.
We now write samples of the size requested by the output audio device.
We also limit the samples we provide to the audio device to however many
bytes are available in its buffer.
The main thread in the WebContent process is often busy with layout and
running JavaScript. This can cause audio to sound jittery and crack. To
avoid this behavior, we now drive audio on a secondary thread.
Note: Browser on Serenity uses AudioServer, the connection for which is
already handled on a secondary thread within LibAudio. So this only
applies to Lagom.
Rather than using LibThreading, our hands are tied to QThread for now.
Internally, the Qt media objects use a QTimer, which is forbidden from
running on a thread that is not a QThread (the debug console is spammed
with messages pointing this out). Ideally, in the future AudioServer
will be able to run for non-Serenity platforms, and most of this can be
aligned with the Serenity implementation.
This creates (and installs upon WebContent startup) a platform plugin to
play audio data.
On Serenity, we use AudioServer to play audio over IPC. Unfortunately,
AudioServer is currently coupled with Serenity's audio devices, and thus
cannot be used in Ladybird on Lagom. Instead, we use a Qt audio device
to play the audio, which requires the Qt multimedia package.
While we use Qt to play the audio, note that we can still use LibAudio
to decode the audio data and retrieve samples - we simply send Qt the
raw PCM signals.
