Add F32/I16x2 conversions to support TDM #27
Conversation
Some dialogue on the Teensy forum raised the issue of support for 24- or 32-bit output; for example see https://forum.pjrc.com/index.php?threads/updated-8x8-and-16x16-audio.75569/post-357275 Obviously not supported by the 16-bit Audio library, but partially supported in this library for I²S and S/PDIF. Since the TDM support usually emits 32-bit samples, forcing use of even-numbered ports only, there is an opportunity to adopt the I/O objects directly by converting two 16-bit TDM port values (containing high and low words) to and from a single F32 stream, giving 24-bit I/O. This commit implements the required objects, plus a minor change to AudioStream_F32 needed for the AudioConvert_I16x2toF32 class.
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I don't currently have a decent example sketch for this, but if encouraged I could do one. I've tested to the best of my ability, but frankly can't easily tell by ear whether I have 16- or 24-bit I/O! |
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Thanks Jonathan for working this up. Neither of the changes should affect existing 16-bit audio. I will merge this in and also update the F32 Audio Design Tool. There is also a do-nothing change for the gain file, that I may be able to remove, but it is a harmless white space change, anyway. If you have an example for TDM handy, that would be good! Bob |
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I updated the F32 design tool to include the two I16x2 classes. Comments are welcomed. Bob |
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That is F32 Design Tool They are on the left under "Convert". |
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Great, thanks Bob. I'll try to put together a simple TDM demo in the next few days. Apologies for the non-change to the gain file, I must have touched it accidentally while sorting out a decent way to get two I16 inputs into the converter, and not noticed when I committed. |
Some dialogue on the Teensy forum raised the issue of support for 24- or 32-bit output; for example see
https://forum.pjrc.com/index.php?threads/updated-8x8-and-16x16-audio.75569/post-357275 Obviously not supported by the 16-bit Audio library, but partially supported in this library for I²S and S/PDIF.
Since the existing TDM support usually emits 32-bit samples, forcing use of even-numbered ports only, there is an opportunity to adopt the I/O objects directly by converting two 16-bit TDM port values (containing high and low words) to and from a single F32 stream, giving 24-bit I/O.
This commit implements the required conversion objects, plus a minor change to AudioStream_F32 needed for the
AudioConvert_I16x2toF32 class.