Before, some loader plugins implemented their own buffering (FLAC&MP3),
some didn't require any (WAV), and some didn't buffer at all (QOA). This
meant that in practice, while you could load arbitrary amounts of
samples from some loader plugins, you couldn't do that with some others.
Also, it was ill-defined how many samples you would actually get back
from a get_more_samples call.
This commit fixes that by introducing a layer of abstraction between the
loader and its plugins (because that's the whole point of having the
extra class!). The plugins now only implement a load_chunks() function,
which is much simpler to implement and allows plugins to play fast and
loose with what they actually return. Basically, they can return many
chunks of samples, where one chunk is simply a convenient block of
samples to load. In fact, some loaders such as FLAC and QOA have
separate internal functions for loading exactly one chunk. The loaders
*should* load as many chunks as necessary for the sample count to be
reached or surpassed (the latter simplifies loading loops in the
implementations, since you don't need to know how large your next chunk
is going to be; a problem for e.g. FLAC). If a plugin has no problems
returning data of arbitrary size (currently WAV), it can return a single
chunk that exactly (or roughly) matches the requested sample count. If a
plugin is at the stream end, it can also return less samples than was
requested! The loader can handle all of these cases and may call into
load_chunk multiple times. If the plugin returns an empty chunk list (or
only empty chunks; again, they can play fast and loose), the loader
takes that as a stream end signal. Otherwise, the loader will always
return exactly as many samples as the user requested. Buffering is
handled by the loader, allowing any underlying plugin to deal with any
weird sample count requirement the user throws at it (looking at you,
SoundPlayer!).
This (not accidentally!) makes QOA work in SoundPlayer.
Brought to you by the inventor of QOI, QOA is a lossy audio codec that
is, as the name says, quite okay in compressing audio data reasonably
well without frequency transformation, mostly introducing some white
noise in the background. This implementation of QOA is fully compatible
with the qoa.h reference implementation as of 2023-02-25. Note that
there may be changes to the QOA format before a specification is
finalized, and there is currently no information on when that will
happen and which changes will be made.
This implementation of QOA can handle varying sample rate and varying
channel count files. The reference implementation does not produce these
files and cannot handle them, so their implementation is untested.
The QOA loader is capable of seeking in constant-bitrate streams.
QOA links:
https://phoboslab.org/log/2023/02/qoa-time-domain-audio-compressionhttps://github.com/phoboslab/qoa
