Develop Reference

Android custom ROM: force software decoders

I'm building a ROM from AOSP, running on Nexus 5X (bullhead).
I wish to completely disable hardware audio/video decoders and make the platform route everything through software - to work exactly the same as on emulator.
I've tried editing audio_policy_configuration.xml and media_codecs.xml to remove decoders, however I'm getting error messages in logcat and no audio is being played - I've no idea if this is even the right direction.

I achieved what I wanted by editing the following in hardware/qcom/audio/hal/audio_hw.c:
static uint32_t out_get_sample_rate(const struct audio_stream *stream)
{
/* struct stream_out *out = (struct stream_out *)stream;
return out->sample_rate;*/
return 44100;
}
static uint32_t out_get_channels(const struct audio_stream *stream)
{
/*struct stream_out *out = (struct stream_out *)stream;
return out->channel_mask;*/
return AUDIO_CHANNEL_OUT_STEREO;
}
static audio_format_t out_get_format(const struct audio_stream *stream)
{
/* struct stream_out *out = (struct stream_out *)stream;
return out->format;*/
return AUDIO_FORMAT_PCM_16_BIT;
}

Communicating with android device from Windows PC via USB

I have android device and windows drivers for it.
I have to communicate using my own binary protocol in accessory mode.
Is it possible to send data to this device without writing custom USB driver?

USB is a complex protocol because it is 'universal' and can handle a large variety of devices (mass storage, cameras,...). So on your android device has to be implemented a basic USB structure to use standard libraries like libusb or something like that.
You can assume that this is the case, because android is in most cases used on processors with USB port.
See http://www.beyondlogic.org/usbnutshell/usb1.shtml.
You can get more information about the USB device classes, interfaces, configurations, endpoints ur android device impmenets by using libusb -v
Then if you know what the USB structure on your android device looks like you can use libusb or another library to write data to specific endpoints in the usb structure by e.g. libusb_bulk_transfer(), libusb_control_transfer()
http://libusb.sourceforge.net/api-1.0/io.html
If you want to program in java you can use usb4java however this is a bit flaky http://usb4java.org/quickstart/libusb.html
The general USB structure is device -> (configuration) -> interface -> endpoint
So the way to write data to an endpoint is:
libusb_init(NULL);
libusb_open_device_with_vid_pid(NULL, vendor_id, product_id);
libusb_claim_interface(devh, 0);
libusb_bulk_transfer(dev_handle, (2 | LIBUSB_ENDPOINT), data,
4, &p, 0); //example
... release interface...
...
libusb_close(devh);
libusb_exit(NULL);
Here is C++ example copied from http://www.dreamincode.net/forums/topic/148707-introduction-to-using-libusb-10/
#include <iostream>
#include <libusb.h>
using namespace std;
int main() {
libusb_device **devs; //pointer to pointer of device, used to
retrieve a list of devices
libusb_device_handle *dev_handle; //a device handle
libusb_context *ctx = NULL; //a libusb session
int r; //for return values
ssize_t cnt; //holding number of devices in list
r = libusb_init(&ctx); //initialize the library for the session we
just declared
if(r < 0) {
cout<<"Init Error "<<r<<endl; //there was an error
return 1;
}
libusb_set_debug(ctx, 3); //set verbosity level to 3, as suggested in
the documentation
cnt = libusb_get_device_list(ctx, &devs); //get the list of devices
if(cnt < 0) {
cout<<"Get Device Error"<<endl; //there was an error
return 1;
}
cout<<cnt<<" Devices in list."<<endl;
dev_handle = libusb_open_device_with_vid_pid(ctx, 5118, 7424);
//these are vendorID and productID I found for my usb device
if(dev_handle == NULL)
cout<<"Cannot open device"<<endl;
else
cout<<"Device Opened"<<endl;
libusb_free_device_list(devs, 1); //free the list, unref the devices
in it
unsigned char *data = new unsigned char[4]; //data to write
data[0]='a';data[1]='b';data[2]='c';data[3]='d'; //some dummy values
int actual; //used to find out how many bytes were written
if(libusb_kernel_driver_active(dev_handle, 0) == 1) { //find out if
kernel driver is attached
cout<<"Kernel Driver Active"<<endl;
if(libusb_detach_kernel_driver(dev_handle, 0) == 0) //detach it
cout<<"Kernel Driver Detached!"<<endl;
}
r = libusb_claim_interface(dev_handle, 0); //claim interface 0 (the
first) of device (mine had jsut 1)
if(r < 0) {
cout<<"Cannot Claim Interface"<<endl;
return 1;
}
cout<<"Claimed Interface"<<endl;
cout<<"Data->"<<data<<"<-"<<endl; //just to see the data we want to
write : abcd
cout<<"Writing Data..."<<endl;
r = libusb_bulk_transfer(dev_handle, (2 | LIBUSB_ENDPOINT_OUT), data,
4, &actual, 0); //my device's out endpoint was 2, found with trial-
the device had 2 endpoints: 2 and 129
if(r == 0 && actual == 4) //we wrote the 4 bytes successfully
cout<<"Writing Successful!"<<endl;
else
cout<<"Write Error"<<endl;
r = libusb_release_interface(dev_handle, 0); //release the claimed
interface
if(r!=0) {
cout<<"Cannot Release Interface"<<endl;
return 1;
}
cout<<"Released Interface"<<endl;
libusb_close(dev_handle); //close the device we opened
libusb_exit(ctx); //needs to be called to end the
delete[] data; //delete the allocated memory for data
return 0;
}
So as your device runs android it has a USB structure/functionality. To investigate the USB functionality of your device (device class like mass storage, RNDIS,...) use libusb -v and the see the code above to write custom data to one of the endpoints on the device.

libusb - How to select an alternate setting of a usb-soundcard for stereo recording?

I have a USB sound card that has the following setup and allows for stereo recording with 48000hz 2 channels 16 bit, so I'm trying to set it up that way:
UsbConfiguration[mId=1,mName=null, mAttributes=160, mMaxPower=50,
mInterfaces=[
UsbInterface[mId=0,mAlternateSetting=0,mName=null,mClass=1,mSubclass=1,mProtocol=0,
mEndpoints=[]
UsbInterface[mId=1,mAlternateSetting=0,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[]
UsbInterface[mId=1,mAlternateSetting=1,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=4,mAttributes=9,mMaxPacketSize=384,mInterval=1]]
UsbInterface[mId=1,mAlternateSetting=2,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=4,mAttributes=9,mMaxPacketSize=576,mInterval=1]]
UsbInterface[mId=1,mAlternateSetting=3,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=4,mAttributes=9,mMaxPacketSize=192,mInterval=1]]
UsbInterface[mId=2,mAlternateSetting=0,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[]
UsbInterface[mId=2,mAlternateSetting=1,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=138,mAttributes=5,mMaxPacketSize=196,mInterval=1]]
UsbInterface[mId=2,mAlternateSetting=2,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=138,mAttributes=5,mMaxPacketSize=294,mInterval=1]]
UsbInterface[mId=2,mAlternateSetting=3,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=138,mAttributes=5,mMaxPacketSize=388,mInterval=1]]
UsbInterface[mId=2,mAlternateSetting=4,mName=null,mClass=1,mSubclass=2,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=138,mAttributes=5,mMaxPacketSize=582,mInterval=1]]
UsbInterface[mId=3,mAlternateSetting=0,mName=null,mClass=3,mSubclass=0,mProtocol=0,
mEndpoints=[UsbEndpoint[mAddress=130,mAttributes=3,mMaxPacketSize=16,mInterval=16]
]
]
I'm trying to select and use the incoming interface with the alternate setting for stereo input and do the same thing with the interface for the stereo output.
For the input, I've tried to do it natively with the following code:
int AndroidUSBAudioIO_start(int sampleRate, int bufferSize, void *callback, void *clientData) {
int rc = -1;
if (androidUSBAudioIO == NULL) {
androidUSBAudioIO = (AndroidUSBAudioIOInternals *) malloc(sizeof(AndroidUSBAudioIOInternals));
}
androidUSBAudioIO->samplerate = sampleRate;
androidUSBAudioIO->buffersize = bufferSize;
androidUSBAudioIO->callback = (audioUSBProcessingCallback *) callback;
androidUSBAudioIO->clientData = clientData;
androidUSBAudioIO->maruStream = 0;
androidUSBAudioIO->isSetup = 0;
androidUSBAudioIO->isPlaying = 0;
rc = libusb_init(NULL);
if (rc < 0) {
}
androidUSBAudioIO->deviceHandle = libusb_open_device_with_vid_pid(NULL, VID, PID);
if (!androidUSBAudioIO->deviceHandle) {
rc = -1;
goto out;
}
rc = libusb_reset_device(androidUSBAudioIO->deviceHandle);
if (rc < 0) {
goto out;
}
rc = libusb_set_configuration(androidUSBAudioIO->deviceHandle, 1);
if (rc < 0) {
}
rc = libusb_kernel_driver_active(androidUSBAudioIO->deviceHandle, IFACE_NUM);
if (rc == 1) {
rc = libusb_detach_kernel_driver(androidUSBAudioIO->deviceHandle, IFACE_NUM);
if (rc < 0) {
goto out;
}
}
rc = libusb_claim_interface(androidUSBAudioIO->deviceHandle, IFACE_NUM);
if (rc < 0) {
goto out;
}
rc = libusb_set_interface_alt_setting(androidUSBAudioIO->deviceHandle, 1, 2);
if (rc < 0) {
printf("libusb_claim_interface: %s.\n", libusb_error_name(rc));
goto out;
}
...
I'm getting the following error at when setting the alternate interface:
Fatal signal 11 (SIGSEGV) at 0x0000001d (code=1), thread 10303
and also tried to do it from java with the following code upon receiving the permission to use the device:
UsbDeviceConnection mUsbDevConn = mUsbManager.openDevice(mAudioDevice);
int mReqType = 0x01; //
int mRequest = 0x0B; // SET_INTERFACE USB SPEC CONSTANT
int mValue = 0x02; // alt settings
int mIndex = 0x01; // interface nr
byte[] mBuffer = null;
int mLength = 0;
int mTimout = 1000;
mUsbDevConn.controlTransfer(UsbConstants.USB_DIR_OUT | mReqType, mRequest, mValue, mIndex, mBuffer, mLength, mTimout);
I'm getting the following error:
Error (status 6: **UNKNOWN**)
What am I missing?

I think it would be highly unusual for the libusb_set_interface_alt_setting call itself to cause the SIGSEGV. I would expect that either a prior call would cause this, or the SIGSEGV is an indirect effect of the call. That is, this call changes the alternate setting, which effectively starts the transfer of audio data. If the buffers, other data structures or the callback are not setup correctly a SIGSEGV may result.
In your situation, I would put more debug messages in the code, including in the library and your callback to try to narrow down the last thing before the crash.
If the code was working for a "mono" device, have a look at what has changed in the move to "Stereo". Perhaps the data-packet size (buffers) needs to be larger.
As far as the Java version is concerned, the error 6 may be related to the fact that you don't seem to be detaching any kernel drivers or claiming the interface before trying to change the alternate setting.
In the past I found it necessary to detach kernel drivers from each and every interface including HID interfaces to free up the allocated bus bandwidth before starting the audio.
Finally, if the free version of usbEffects (Android App) works with this device, you can connect adb to the phone via Wi-Fi and run the app with the device connected to see the debug messages that will tell if the requestType, request etc parameters are correct for this hardware.

Android & libusb submit ISOC transfer error

I write the Android application using libusb-1.0.9 and NDK (Android 4.0.4+) which has to read out audio-data from the USB-audiocard. The USB device from libusb opens successfully, and for it it is possible to receive all interfaces/EndPoint list. But when making ISOC transfer I faced with following unclear me error:
Debugging C code of making transfer:
static uint8_t buf[12];
static void cb_xfr(struct libusb_transfer *xfr)
{
LOGD("USB callback\n");
libusb_free_transfer(xfr);
}
JNIEXPORT jlong JNICALL
Java_com_usbtest_libusb_Libusb_makeISOCTransfer(JNIEnv *env, jobject this, jlong ms)
{
static struct libusb_transfer *xfr;
int num_iso_pack = 1;
unsigned char ep = 0x84;
xfr = libusb_alloc_transfer(num_iso_pack);
if (!xfr) {
LOGD("libusb_alloc_transfer: errno=%d\n", errno);
return -1000;
}
LOGD("libusb_fill_iso_transfer: ep=%x, buf=%d, num iso=%d\n", ep, sizeof(buf), num_iso_pack);
libusb_fill_iso_transfer(xfr, handle, ep, buf, sizeof(buf), num_iso_pack, cb_xfr, NULL, 0);
libusb_set_iso_packet_lengths(xfr, sizeof(buf)/num_iso_pack);
int res = libusb_submit_transfer(xfr);
LOGD("libusb_submit_transfer: %d, errno=%d\n", res, errno);
struct timeval tv;
tv.tv_sec = 1;
tv.tv_usec = 0;
libusb_handle_events_timeout(NULL, &tv);
return res;
}
After a call of libusb_submit_transfer I received a mistake: libusb_submit_transfer: -1, errno -2
And text messages:
need 1 32k URBs for transfer
first URB failed, easy peasy
EndPoint 0x84 is true for audio-in. The buf[] size = 12 - corresponds to the field wMaxPacketSize of this EndPoint. I request 1 transfer. Field of xfr->status = 0, but callback isn't caused.
I thought that it is necessary to increase the buf buffer to 32K - I increased, but it didn't help.
I tried to increase quantity of transfers. Same error.
Prompt me please in what there can be a error?

I found the solution of this problem.
In this topic http://en.it-usenet.org/thread/14995/14985/ there was a similar question, and the decision appeared to make detach for device HID USB interfaces.
I've used libusb_detach_kernel to detach the 2 hid drivers and submit
transfer returned 0!!
I made libusb_detach_kernel_driver(handle, interface) for all interfaces of the device (0..3) after device opening, and as a result of libusb_submit_transfer return SUCCESS of transfer.

Android app restarts automatically after a crash

My app is partly written in native app using C/C++. The problem is that whenever C/C++ part crashes for some reason the app dies and then restarts automatically. This causes all kinds of messy problems
Now of course, it should not crash in the native part and I'm trying to weed out all reasons why it would happen. However, if it does happen I'd like to:
Quit gracefully
If it does die, at least not try to restart automatically.
I'm curious as to why this behaviour happens. After some search I tried putting the following line in the main activity element of the AndroidManifest.xml:
android:finishOnTaskLaunch="true"
but the automatic restore still happens.
Anyone knows why this is happening and how to change it?
UPDATE:
I think a more fundamental question is,
Is there something similar to a callback if there is a native crash?
One of the answers suggested 'handling crash signals'. I'd be grateful for any links on how it can be done at an application or module level.
As it stands currently, if there is a crash the app just disappears, there's nothing in logcat, so no debugging is possible.

Try to handle crash signals (SIGSEGV etc.) and send kill to yourself in signal handler. This trick helps me.
Example:
#include <signal.h>
#include <unistd.h>
static void signal_handler(int signal, siginfo_t *info, void *reserved)
{
kill(getpid(),SIGKILL);
}
extern "C" jint JNI_OnLoad(JavaVM* vm, void* /*reserved*/)
{
struct sigaction handler;
memset(&handler, 0, sizeof(handler));
handler.sa_sigaction = signal_handler;
handler.sa_flags = SA_SIGINFO;
sigaction(SIGILL, &handler, NULL);
sigaction(SIGABRT, &handler, NULL);
sigaction(SIGBUS, &handler, NULL);
sigaction(SIGFPE, &handler, NULL);
sigaction(SIGSEGV, &handler, NULL);
sigaction(SIGSTKFLT, &handler, NULL);
return(JNI_VERSION_1_6);
}
UPDATE2
if you want to see crashlog in android logcat you should use this signal handler
static void signal_handler(int signal, siginfo_t *info, void *reserved)
{
struct sockaddr_un addr;
size_t namelen;
socklen_t alen;
int s, err;
char name[] = "android:debuggerd";
namelen = strlen(name);
// Test with length +1 for the *initial* '\0'.
if ((namelen + 1) > sizeof(addr.sun_path)) {
errno = EINVAL;
return;
}
/* This is used for abstract socket namespace, we need
* an initial '\0' at the start of the Unix socket path.
*
* Note: The path in this case is *not* supposed to be
* '\0'-terminated. ("man 7 unix" for the gory details.)
*/
memset (&addr, 0, sizeof addr);
addr.sun_family = AF_LOCAL;
addr.sun_path[0] = 0;
memcpy(addr.sun_path + 1, name, namelen);
alen = namelen + offsetof(struct sockaddr_un, sun_path) + 1;
s = socket(AF_LOCAL, SOCK_STREAM, 0);
if(s < 0) return;
RETRY_ON_EINTR(err,connect(s, (struct sockaddr *) &addr, alen));
if (err < 0) {
close(s);
s = -1;
}
pid_t tid = gettid();
if(s>=0)
{
/* debugger knows our pid from the credentials on the
* local socket but we need to tell it our tid. It
* is paranoid and will verify that we are giving a tid
* that's actually in our process
*/
int ret;
RETRY_ON_EINTR(ret, write(s, &tid, sizeof(unsigned)));
if (ret == sizeof(unsigned)) {
/* if the write failed, there is no point to read on
* the file descriptor. */
RETRY_ON_EINTR(ret, read(s, &tid, 1));
//notify_gdb_of_libraries();
}
close(s);
}
wait(NULL);
kill(getpid(),SIGKILL);
}
I took it from android source (can't insert link because android.git.kernel.org is down), but I am not sure that it will work in future Android releases

By default your application should not be automatically restarting. Generally one would have to register for this kind of thing, e.g. via the AlarmManager/keep alives.
Do you have a service as part of your application?