Cause Analysis and Solution for switching between stereo and single channel during video playback by android

Some customers use third-party video players and switch between stereo and single channels. After the switch, it is found that it does not work.
The reason is that by default, the HAL layer does not handle the commands sent from stereo to mono, so it will be ineffective,

You can add related processing as follows:
1. Modify AudioMTKHardware. cpp.
Add: static String8 keySetStereo2MonoMode = String8 ("EnableStereoOutput ");

2. Modify status_t AudioMTKHardware: setParameters (const String8 & keyValuePairs)
In EXIT_SETPARAMETERS:
Previously added:Copy codeThe Code is as follows: if (param. getInt (keySetStereo2MonoMode, value) = NO_ERROR ){
ALOGD ("setParameters (): % s value = % d", keyValuePairs. string (), value );
(AudioMTKStreamManager *) mAudioMTKStreamManager)-> ForceSterer2Mono (value );
}

3. Modify AudioMTKStreamManager. h
Add public method definition:Copy codeThe Code is as follows: status_t ForceSterer2Mono (bool flag );
Status_t AudioMTKStreamManager: ForceSterer2Mono (bool flag)
{
// Force all stream to standby
ALOGD ("ForceSterer2Mono = % d", flag );
If (mStreamOutVector. size ()){
For (size_t I = 0; I <mStreamOutVector. size (); I ++ ){
AudioMTKStreamOut * pTempOut = (AudioMTKStreamOut *) mStreamOutVector. valueAt (I );
PTempOut-> SetStereoToMonoFlagForce (flag );
}
}
Return NO_ERROR;
}

4. Modify AudioMTKStreamOut. h
T add definition:Copy codeThe Code is as follows: status_t SetStereoToMonoFlagForce (bool flag );
Status_t AudioMTKStreamOut: SetStereoToMonoFlagForce (bool flag)
{
ALOGD ("SetStereoToMonoFlagForce = % d", flag );
MSteroToMono = flag;
Return NO_ERROR;
}