Read / Write non interleaved data ?

[JulienH2000]

Hello,
maybe I'm missing something, but looking at the documentation, it looks like the crate as no method to handle non-interleaved PCM.
The crate provides both writei and readi method for io object, but shouldn't it be some writen and readn method ?
As both writei and readi return a single buffer, they're incompatible with non-interleaved data, and curiously the crates does provide RWNonInterleaved PCM Access type..
Is it just not done in the crate ? (meaning readn/writen should be custom build as C bindings form the C alsa lib), or is there a specific way to read or write non-interleaved multiple buffers using only crate-provided method ?

Thanks a lot !

[diwic]

Hi,

non-interleaved access is quite uncommon these days, so I have not written specific code to support it. But you can use PCM::io_bytes which will accept any format, both interleaved and non-interleaved.

(This should be better documented though)

[JulienH2000]

Ok thanks ! Looks like the easiest would be to extract the channels into multiple with simple array/vector manipulation from an interleaved buffer. Is readn or writen in the roadmap to be implemented ?
Thanks a lot !

[diwic]

Ok thanks ! Looks like the easiest would be to extract the channels into multiple with simple array/vector manipulation from an interleaved buffer. Is readn or writen in the roadmap to be implemented ? Thanks a lot !

I'm not planning on implementing it. PR is welcome though :-)

[JulienH2000]

Thanks for your reply.
I'd love to contribute and implement this, but I'm clueless about ffi / binding generation. If it's not implemented in the long run, I'll try to PR this :)
In the other hand, I'm adding this comment regarding something that hit me while implementing a LPF filter in my project :
It is critical to have non-interleaved buffer, not only for better multichannel handling, but mostly as almost every "discret signal" DSP algorithms (ie: sample to sample algorithms) need continuous sample flow to iterate over. So interleaved buffers have to be desinterleaved prior to any DSP, and interleaved back before writting out. (As it is, wasting ressource and latency with array manipulation).
I hope this will be useful regarding the development of this great crate 👍

[diwic]

@JulienH2000 Most soundcards only support interleaved buffers, so if you're able to set noninterleaved, then the alsa library might do the interleaving for you behind the scenes. plughw and others might do that whereas hw would not.

[diwic]

Probably fixed in #134 , reopen if not. Thanks!