PocketMagic

Android Native Play Sound using /dev/msm_pcm_out By Radu Motisan Posted on November 18th, 2010 , 1623 Views (Rate 1.77)

Following my previous article, where I presented that it is possible to write a native C application to directly extract the screen's framebuffer data and save it as a BMP, for the purpose of making screen captures, I will give another example of using the NDK to compile a C code that would play sounds on your Android, by directly interfacing the PCM device: /dev/msm_pcm_out

There is an old sample in the Google Android code that does just that and more: playwav.c . It can be compiled using the NDK and Cygwin, as presented here:

Simply copy the binary to your Android, and play a wave file by calling:

./playsound -play learn.wav

Easy, and a nice surprise to hear sounds coming from your Android, without having any top level interfaces running for that purpose.
The project files:
NativePlayWav

More on PocketMagic:

Programmatically Injecting Events on Android - Part 1

Atmega8 and enc28J60 for ethernet support

How to set the AVR Fusebits

ATMega128 and HD44780 LCD using 3 Wires with the 74HC164

CDV-742 Dosimeter and CDV-750 Dosimeter Charger

Dual H-Bridge for controlling two motors

November 18th, 2010 | Tags: Android, native code, ndk, playsound | Category: Android, Software |  Print This Post |  Email This Post | Subscribe to comments | Leave a comment | Trackback URL

6 Responses to “Android Native Play Sound using /dev/msm_pcm_out”

1. 
   1
   Victor:
   February 1st, 2011 at 2:36 pm

   Hey Radu,

   I don’t have rwx access in /data/data, I only have rw- in /sdcard .
   I tried using abd root, but I get an error: adbd cannot run as root in production builds

   Any hints on how I could test your app ?

   10x

2. 
   2
   Radu Motisan:
   February 1st, 2011 at 2:41 pm

   Hi Victor, thanks for dropping by.

   I don’t think you will be able to get this work , if you don’t have root access, since the little native code needs access to /dev/msm_pcm_out

   By any chance can you try it on a different phone, or ROOT you own?

3. 
   3
   Victor:
   February 3rd, 2011 at 7:04 pm

   Hi Radu,
   Thanks for the quick answer and sorry for my delayed one .
   I wanted to write an app that would work on standard issue Android devices. I guess I’ll have to use the latest NDK for low-latency sound playback and target phones having at least v2.3.
   Thanks again for everything!

4. 
   4
   Anandhi:
   January 12th, 2012 at 5:57 am

   Hi Radu,

   I just came across this, and though I am new to the environment, was able to get through most of the above steps. I wish to test this on the android emulator, and then add some processing code to the file before getting it onto a phone. However on the emulator, when i get to the “chmod +x playwav” step i get the error “bad mode”. And if i try “./playwav -play learn.wav” anway, i get the message “pcm_play: cannot open audio device: No such file or directory”. Could you help me run this on the emulator, please?

   Thanks a lot.

5. 
   5
   Fred:
   March 15th, 2012 at 11:41 pm

   I have same problem like you “cannot open audio device: No such file or directory” is because i have old android (2.2 froyo)? any body confirm if /dev/msm_pcm_out is found in froyo ?
   i am using “samsung galaxy S”.

   Thanks.

6. 
   6
   Anonymous:
   June 21st, 2012 at 2:27 pm

   Hi,
   I have /dev/msm_pcm_out, but playwav does not play anything at all.
   I get no errors, it just fills buffers and then gets stuck trying to fill more buffers, but obviously they never empty.
   I’m using an Htc Desire Z.
   Thanks

Thank you for commenting. Your comment won't show until approved, which can take some time.