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Playing audio files on the micro:bit
Posted: Mon Mar 27, 2017 7:40 pm
by fizban
I have been experimenting with the audio module. The example provided in the documentation opens the possibility to play audio files. I have not been able to store files larger than 4KB so the only solution I have found is to split larger files into 4KB chunks. This can be easily done in Audacity with
Analyze-Regular interval labels and then
File-Export Multiple. Although the values accepted by the audio.play function are supposed to be signed bytes between -128 and 127 I have been successful exporting the files in raw format, header-less, with unsigned 8 bits PCM. They sound quite OK on the micro:bit.
Assuming around 30KB of storage, at a 8KHz sampling frequency it gives around 3.5 seconds of recording sound.
Here is a sample code to play the attached files. They are based on the sound at
https://www.freesound.org/people/urupin/sounds/199905/ , which has a CC0 license.
Code: Select all
import audio
def read_frame(f_list, frame):
for file in f_list:
ln = file.readinto(frame)
while ln:
yield frame
ln = file.readinto(frame)
def play_file(f):
with open(f + "-01.raw", "rb") as file1, \
open(f + "-02.raw", "rb") as file2, \
open(f + "-03.raw", "rb") as file3, \
open(f + "-04.raw", "rb") as file4:
f_list = [file1, file2, file3, file4]
audio.play(read_frame(f_list, frame), wait=True)
# Allocate memory outside the interrupt
frame = audio.AudioFrame()
ln = -1
file = 1
# play the files
play_file("robot")
Anyone can think of a way of storing more than 3.5 seconds (without using an external sd card)? I was thinking on some kind of basic ADPCM, but it seems that the 2ms that the interrupt has to process the sound is not enough to do even a simple loop through the 32 elements of the AudioFrame...
Re: Playing audio files on the micro:bit
Posted: Tue Mar 28, 2017 7:28 am
by deshipu
I think that you can connect an SD card over SPI to the microbit. Not sure if it's possible to mount it as a filesystem, but in the worst case you can simply read raw blocks of data from it. An SPI flash or EEPROM chip would work too.
Re: Playing audio files on the micro:bit
Posted: Tue Mar 28, 2017 7:57 am
by fizban
Thanks, deshipu. Yes, that is the alternative I was thinking of as well, but I was wondering whether it would be possible to store the information in a more efficient way in the micro:bit without the need of external storage devices and also be able to fit the decompression routine within the interrupt in python... Being able to store up to 10 seconds would be nice...
I believe this
little thing has less than 4K and stores 10s. I know it is not comparable, but if I have to use an external device, I would probably use an
external mp3 player...
Re: Playing audio files on the micro:bit
Posted: Mon Jun 15, 2020 2:01 pm
by olliec002004
Hi people,
Im very much new to microbit and python.
Im trying to make an electric drum kit for my mate to play in a band
My question is how can I get the microbit to play drum audio files through a regular speaker and quarter inch jack and crocodile clips as shown in LINK. "completed circuit" with ground will play the sound.
cheers. modified code of version above would be very helpful.
https://www.youtube.com/watch?v=bm7MGKspk0o
Re: Playing audio files on the micro:bit
Posted: Sun Jan 17, 2021 3:56 pm
by slowDan
Sorry to dig up an old post!
I'm trying to get this working myself, but the Python Editor tells me I can only add .py or .hex files to the file system.
I tried renaming the files to .hex but then it just says that they don't contain any valid python code. Had to be worth a try!
Anyone have any clues on how to cheat the editor?
Re: Playing audio files on the micro:bit
Posted: Mon Jan 18, 2021 4:31 am
by jimmo
slowDan wrote: ↑Sun Jan 17, 2021 3:56 pm
Sorry to dig up an old post!
I'm trying to get this working myself, but the Python Editor tells me I can only add .py or .hex files to the file system.
I tried renaming the files to .hex but then it just says that they don't contain any valid python code. Had to be worth a try!
Anyone have any clues on how to cheat the editor?
Which editor are you using?
The background is that the micro:bit is programmed with a .hex file which is the complete firmware. When you use MicroPython, the generated .hex file is the MicroPython runtime combined with an encoded copy of your Python script. Any micro:bit aware editor will be able to generate this .hex file for you from your Python code. I mostly recommend Mu --
https://codewith.mu/
Re: Playing audio files on the micro:bit
Posted: Sun Feb 28, 2021 9:21 pm
by mfitzp
The example above (and this
https://gist.github.com/nbogie/4b2e68e1 ... 32b9c38ece ) doesn't seem to work with the new Microbit v2 boards with the built-in speaker -- there is audio, but it's completely distorted/crackling as you'd expect with a mismatch in the format and plays about 2x too long.
I've tested the example robot (R2D2) audio above and my own audio -- I've attached a comparison between the R2D2 audio, and what comes out of the speaker.
The v2 docs all suggest the AudioFrame format/etc. are the same as far as I can see + the built in sounds e.g. `Sound.YAWN` work fine and sound clear. Any ideas?