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8 channel wav poly recording working

A project log for Multichannel Audio DSP Field Mixer Recorder

USBmidi, bluetooth app controll 8 chan portable DSP mixer.balanced audio IO,phantom power,flexible routing,ISO recording. networked Timecode

ben bilesben biles 07/24/2018 at 00:380 Comments

8 channel wav poly 16bit recording is working in TDM8 mode !!!!!!!

no 24bit or 32bit yet but I can see how to make that work now. Its a question of making the SAI port 32bit , then the buffer and DMA channel 32bit ( WORD )

Its been interesting to work on. There is no timing as such in the application. the data just comes in over DMA and is dumped into a file.

Its the PCM wav record format header that describes channel count , bit rate , sample rate.

I thin the player might be more complex as it has to read the WAV file header and then playback in appropiate sample rate bitrate etc

There is the odd click and glitch in the recording , so I'm going to play about with buffer sizes and DMA priority etc until I

smooth out those problems then I'll add 24 and 32bit capability.


I'll need to go to TDM16 also to record the mix track as well as the independent channels.

I'm not sure where the transfer speed limit of usb host is but stm32f7 supports high speed , so the limit might the usb stick itself.

8 channels of 16bit audio

8 channels 16bit mono
48000 x 16 bytes
768kBsec x 30 seconds =  23040000 bytes , ADD 44 bytes for the WAV header = 23040044 bytes 30 sec

the minimum i need will be around double that in 24bit mode and including a 2 channel mix track
Should be ok , its under 3MByte/sec write speed.

I haven't really thought about a playback ( review ) and how to do that . I suppose could just pipe the 8 channels back into the DSP mixer so you can preview any recorded channel or the mix. not really sure yet. I could have a kind of mix playback mode..

The recorder / player commands just about work in the bluetooth app. I should disable the TS/screen soon though as it could be the cause of the small glitches in the recording. really I need to send some data back to the bluetooth app suck as record time player recorder app state etc.

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