Re: Driving a USB device at 32 bits per sample
Re: Driving a USB device at 32 bits per sample
- Subject: Re: Driving a USB device at 32 bits per sample
- From: Philippe Wicker <email@hidden>
- Date: Wed, 04 Apr 2018 17:12:08 +0200
From the screenshot of AMS it seems your device is operating at 32 bits per
sample. AMS just shows what the USB descriptors are telling of the device
capability. If you have a USB analyser you could check that directly on the
bus.
> On 4 Apr 2018, at 16:44, Paul Sanders <email@hidden> wrote:
>
> Yes, that's all true, but not relevant (well, not to me). I want the device
> to be operating in 32 bit mode, regardless of how Core Audio actually
> delivers the data.
>
> Paul Sanders.
>
>
> On 04/04/2018 15:09, Philippe Wicker wrote:
>
> AFAIK CoreAudio don’t allow a user to get the raw samples from the device, it
> always provide audio data with a 32 bit float format (single precision).
> Device native PCM data are converted at some point (within the driver? Or
> maybe in the HAL?) to this float format before being delivered to the user.
> It’s also true in the other direction, you have to provide 32 bit float to
> the device. These float data are converted to whatever the device needs at
> some point. If you need to get or send raw data then you are limited to 24
> bit integer which is the largest bit-size you can encode in a lossless manner
> within a float (24 bits is the size of the float mantissa).
>
> ...
>
>
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