Good idea! A few thoughts pre-review:

• The doc should probably say that if a buffer is not passed in, a buffer of 512 bytes (or say that two buffers of 256 bytes) will be used. This will give the user guidance about how big to make the buffer.
• Should one buffer that's split be passed, or two? If two, the smaller of the two will determine the length used. (Or they could be required to be of equal length). The advantage of two buffers is that they might be easier to allocate in the face of fragmentation. The internal implementation allocates two buffers separately. On the other hand using a larger buffer that later gets freed would reduce fragmentation later.

Good point about documenting the default size, I will add that.

I went for a single buffer mostly because it simplifies the usage, and lets us skip explaining what double buffering is. I'm not worried about memory fragmentation, because it's going to be allocated at the beginning of your program anyways.

By the way, experiments show that a much smaller buffer than 512 seems to be working just fine, so we might want to reconsider the default.

I suppose the optimal buffer size depends on the bit rate.

I suppose the optimal buffer size depends on the bit rate.

And speed of processor, and what other background tasks are happening, so it's probably hard to specify without experimentation.

All the better to have it user-controlled.

@dhalbert Please merge if you don't want to review.

I actually just realized that I didn't add the information about default buffer size to the documentation. I will do that tomorrow.