I've been struggling with this over 40 days for at least 5-6 hours a day
and ready to pay for the solution or even agree on some sort of long term
revenue agreement from the revenue my app would generate on the phones that
the solution would work.
I have a call recording app that uses VOICE_CALL audio source. Although
ASOP does not implement/mandate it, most manufacturers have implemented
VOICE_CALL and apps that use VOICE_CALL audio source worked fine on many
devices. That is until Android 6.
Google changed this behavior with Android 6. Opening VOICE_CALL audio
source now require android.permission.CAPTURE_AUDIO_OUTPUT which is only
granted to system applications.
This essentially stops call recording, or it should have. Well, it does for
mine and 200+ other call recording apps apart from 3 who have found a way
to get around this limitation.
I have been trying those apps on many different phones with Android 6 and
found out certain characteristics in the way they manage to record.
They all use Android AudioRecord class and open MIC audio source. I do too;
but on my app, I only get audio from MIC, not the other party. What I've
found out is telling me that they are issuing some sort of system call just
after or before starting recording.
Have a look at the following log form one of the apps that successfully
record VOICE_CALL, even though it uses MIC to record. It looks like app is
some how managing to mix/route/stream/merge VOICE_CALL audio source in to
MIC.
- D/audio_hw_primary: in_set_parameters: enter:
kvpairs=input_source=1;routing=-2147483644
- D/PermissionCache: checking android.permission.MODIFY_AUDIO_SETTINGS
for uid=10286 => granted (432 us)
- D/audio_hw_primary: in_set_parameters: enter:
kvpairs=input_source=4;routing=-2147483584;format=1
- D/audio_hw_primary: select_devices: out_snd_device(0: )
in_snd_device(283: voice-dmic-ef)
- D/hardware_info: hw_info_append_hw_type : device_name = voice-dmic-ef
- D/voice: voice_get_incall_rec_snd_device: in_snd_device(283:
voice-dmic-ef) incall_record_device(283: voice-dmic-ef)
As you can see in the first line it is starting with MIC audio source
input_source=1;routing=-2147483644.
Then, on the second line it does something and get granted
android.permission.MODIFY_AUDIO_SETTINGS which is normal permission and my
app has it too. This seems to be the most important part and it looks like
all 3 are using JNI to do what ever they do to trigger streaming/merging of
VOICE_CALL audio source to MIC and record with standart AudioRecorder API
On the next line you see that audio hardware starting to mixing VOICE_CALL
(input_source=4) even though they have opened MIC(1) audio source.
I have assumed they used
AudioManager.setParameters("key=value")
and tried many variations such as
AudioManager.setParameters("input_source=4;routing=-2147483584;format=1")
without any luck.
Then, I've found
http://stackoverflow.com/questions/28738101/android-ndk-audio-routing-forcing-audio-through-the-headset
and thought they might be some how mix/route/stream/merge VOICE_CALL in to
current AudioRecord session and (since have no C knowledge) tried to use
reflation to achieve same thing with below code (again) without luck.
private static void setForceUseOn() {
/*
setForceUse(int usage, int config);
----usage for setForceUse, must match AudioSystem::force_use
public static final int FOR_COMMUNICATION = 0;
public static final int FOR_MEDIA = 1;
public static final int FOR_RECORD = 2;
public static final int FOR_DOCK = 3;
public static final int FOR_SYSTEM = 4;
public static final int FOR_HDMI_SYSTEM_AUDIO = 5;
----device categories config for setForceUse, must match
AudioSystem::forced_config
public static final int FORCE_NONE = 0;
public static final int FORCE_SPEAKER = 1;
public static final int FORCE_HEADPHONES = 2;
public static final int FORCE_BT_SCO = 3;
public static final int FORCE_BT_A2DP = 4;
public static final int FORCE_WIRED_ACCESSORY = 5;
public static final int FORCE_BT_CAR_DOCK = 6;
public static final int FORCE_BT_DESK_DOCK = 7;
public static final int FORCE_ANALOG_DOCK = 8;
public static final int FORCE_DIGITAL_DOCK = 9;
public static final int FORCE_NO_BT_A2DP = 10;
public static final int FORCE_SYSTEM_ENFORCED = 11;
public static final int FORCE_HDMI_SYSTEM_AUDIO_ENFORCED = 12;
public static final int FORCE_DEFAULT = FORCE_NONE;
*/
try {
Class audioSystemClass =
Class.forName("android.media.AudioSystem");
Method setForceUse = audioSystemClass.getMethod("setForceUse",
int.class, int.class);
setForceUse.invoke(null, 0, 0); // setForceUse(FOR_RECORD,
FORCE_NONE)
} catch (Exception e) {
e.printStackTrace();
}
}
Obviously there is something I am missing that makes recording possible.
I even offered to pay to get this information, all refused. Fair enough
I've said. I will be publishing it once/if I find it!
Do you have any idea as to what they might be doing?
Thanks in advance.
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