Enable mp3 output on esp32s3 #9218
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
.. just to prevent background tasks from running
it's the standard i2s format, and what's needed for max98357 breakout.
.. so that the underlying allocations will be freed. This is not important now but will be if the underlying allocator is changed to something else like `port_malloc` in the future.
.. espressif will be able to put the mp3 data in faster RAM this way.
These changes have been requested upstream at adafruit/Adafruit_MP3#21
gcc -fsanitize=undefined reports diagnostics like these: ``` ../../src/bitstream.c:93:36: runtime error: left shift of 177 by 24 places cannot be represented in type 'int' ../../src/imdct.c:86:53: runtime error: left shift of negative value -937 ``` -fwrapv provides implementation-defined behavior that matches the expectations of two's complement arithmetic.
tannewt
requested changes
May 1, 2024
tannewt
requested changes
May 2, 2024
Co-authored-by: Scott Shawcroft <scott@tannewt.org>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
With these changes I can successfully play a 48kBit/s, 22.5kHz, mono test file on the Adafruit Feather ESP32-S3 TFT using a max98357 breakout, which takes less than 10% of available CPU times. I have not tried higher bit rates, stereo playback etc., so I don't know the performance limits.
There are occasional audio glitches, which mostly correlate with the feather's charging LED. I think this is a HW problem but it's difficult to be sure.
This also fixes the problem that all I2S output was in a non-standard format since updating esp-idf (to 5.0? 5.1?). Now, the "philips standard" format is used again.
This needs adafruit/Adafruit_MP3#21
I made sure that my test program does not generate garbage while playing. The maximum I2S DMA buffer size is only about 1000 samples, or only about 20ms @ 48kHz. blocking background tasks will make the audio glitch, and garbage collection blocks background tasks. This is a larger problem on microcontrollers with PSRAM, like the feather s3 series, because the collection time is proportional to the size of the GC heap.
This also doesn't work on a debug build, the different optimization flags or additional error checking seemed to just add too much overhead to play back without glitching.