Adding USB-audio feedback and mute command to usb_sound_card.c #53
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USB-audio feedback (USB AudioStreaming Isochronous Feedback) is indispensable for stable sound playback without clicking noise. I added simple feedback function by checking the vacancy of the buffer. To avoid modifying other sources (such as audio.cpp in pico-extras), number of free buffers is checked in this source code. USB audio also has mute function (mute without changing volume value). I also added this function (in the original source code, it is almost done, so I added just three lines).
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I noticed something should be improved more, so I will check throughly and redo it. |
Reviewed and tested again. Feedback is properly working.
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USB-audio feedback (USB Audio Streaming Isochronous Feedback) is indispensable for stable sound playback without clicking noise. I implemented a simple feedback function by monitoring the buffer's vacancy. To avoid modifying other sources (such as audio.cpp in pico-extras), the number of free buffers is checked directly within this source code.
USB audio also includes a mute function (mute without changing the volume value). I enhanced this functionality by adding just three lines of code, as the original source code was almost complete.
Many DIY USB-DAC enthusiasts have been eagerly anticipating the implementation of the feedback function. The modified parts are isolated using switches named USB_FEEDBACK and MUTE_CMD. Please check it out.