Thanks for the feedback. I've done a little more work on it - I
rewrote the original read/write functions so they now take a `'a array
array` and I renamed my Bigarray implementations to stream_write_ba
and stream_read_ba. I also added functions to retrieve information on
the Host API and devices.
I've been considering adding additional type info to the stream type.
For example, if you open a stream with the format `Format_float32`,
the type returned would be `float stream`, or possibly something more
complex like ('float, Format_float32, non_interleaved) stream. That
way the type system would ensure that you never try to using a float
array on a Format_int32 stream. I'm pretty sure this can be added
without the need to change any code that is currently using the
portaudio library as well.
Additionally I feel that it might be best to remove the code I've
added for callbacks. I should do some more testing on a faster
computer, but as I mentioned it's rather fragile on my netbook. Given
the limited usefulness of the feature and the fact that it requires
OCaml 3.12 and linking to the thread library, I think the cons
outweigh the pros. Perhaps it could be a compile time check?
Finally, I noticed that `open_stream` is commented out in the mli
file. Is there a reason for this?
-Niki Yoshiuchi
On Tue, Mar 15, 2011 at 8:15 PM, Romain Beauxis <[email protected]> wrote:
> Hi again!
>
> 2011/3/15 Niki Yoshiuchi <[email protected]>:
>> I've been using ocaml-portaudio for some pitch-detection software I'm
>> working on. I noticed that some functionality was missing and decided
>> to add it in. Specifically I've been working on: different formats,
>> callbacks and using Bigarrays.
>>
>> I don't know how useful callbacks are - if the execution of the
>> callback takes too long portaudio will silently fail (pun intended).
>> On my machine (an EeePC 1000H) the callback couldn't handle much more
>> than a Bigarray.blit. Generating random noise, for example, would
>> cause the thread to terminate execution after a few seconds. This
>> also requires OCaml 3.12 and the use of threads.
>
> I have no idea if callback are useful but I see that the code for this
> seems very clean and makes use of the thread registration API provided
> by ocaml 3.12. Very nice :-)
>
> My only remark would be about the use of printf which is probably
> temporary for debugging..
>
>> The other significant change I've made is switching to Bigarrays.
>> This results in far less copying of data and allows for almost
>> seamless use of non-interleaved arrays. I have noticed that Liquid
>> Soap uses float array arrays extensively and that Bigarrays will break
>> compatibility. While I have currently rewritten the read and write
>> functions to use Bigarrays I can easily support both in order to not
>> break compatibility. However this leads me to wonder (and forgive me
>> if this is an ignorant question, I don't use Liquid Soap and only
>> briefly looked through the source) why float array arrays are used
>> over Bigarrays given that Bigarrays are compatible with C.
>
> I think the answer is that we consider that copying float arrays is
> negligable compared to the advantage of being able to manipulate
> directly floats in OCaml code in Liquidsoap.
>
> For video data, however, we are using bigarrays because copying data
> is just not an option there..
>
> It would be nice indeed to have a backward compatibility API. You may
> switch the main function to bigarray and provide an alternative _f API
> though..
>
>> My code can be found on github:
>> https://github.com/aplusbi/ocaml-portaudio Some functionality is
>> still missing or untested, but please let me know if any of this work
>> is of use to Savonet.
>
> I think we would be pleased to incorporate your changes once you are
> done. I also believe that we would be pleased to give you commit
> access to our repository if you wish to work directly there..
>
> Romain
>
>> Thanks,
>> Niki Yoshiuchi
>>
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