Bugzilla

Some additional log:
```
Gecko   : [Child 14829: MediaDecoderStateMachine #1]: E/cubeb cubeb.c:386:Invalid format, 0x809d2fcc 0x0 1 0
Cubeb_OpenSL: Playback params: Rate 48000, channels 2, format 2, latency in frames 4800.
```

After some digging, I found the key reason is opensl is incompatible with f32 when minsdk <= LOLLPOP.

From this  [commit](https://hg.mozilla.org/mozilla-central/rev/0a0ec1730ddb#l2.13) (bingo, i guessed right) , Audio output format is  AUDIO_OUTPUT_FORMAT = AUDIO_FORMAT_FLOAT32 ,  will be converted to `CUBEB_SAMPLE_FLOAT32NE` (format 2 in the second line of the log) for cubeb.
```
params.format = CubebUtils::ToCubebFormat<AUDIO_OUTPUT_FORMAT>::value;

template <AudioSampleFormat N>
struct ToCubebFormat {
  static const cubeb_sample_format value = CUBEB_SAMPLE_FLOAT32NE;
};
```

then the keypoint https://searchfox.org/mozilla-central/source/media/libcubeb/src/cubeb_opensl.c#1108-1130

if `__ANDROID_API__` <  ANDROID_VERSION_LOLLIPOP , `opensl_set_format_ext` is not defined and will not be called, so `format` is NULL , then `opensl_set_format` will be called. In `opensl_set_format` , only ` CUBEB_SAMPLE_S16LE` and ` CUBEB_SAMPLE_S16BE` will be handled, other format will cause  CUBEB_ERROR_INVALID_FORMAT. then Audio failed to initialize.

When targetting armeabi  , the `__ANDROID_API__` is 16 (because of --target=arm-linux-androideabi16) < ANDROID_VERSION_LOLLIPOP  (21)  , so failure occurs.

When targetting arm64  , the `__ANDROID_API__` is 21 (because of --target=aarch64-linux-android21) ==  ANDROID_VERSION_LOLLIPOP  (21) , so format is assigned by `opensl_set_format_ext`.


-------------------------
Although i don't know 1) why `opensl` is still used in Android 11. 2)  why ndk targetting to API 16 when building armeabi.

Some additional log:
```
Gecko   : [Child 14829: MediaDecoderStateMachine #1]: E/cubeb cubeb.c:386:Invalid format, 0x809d2fcc 0x0 1 0
Cubeb_OpenSL: Playback params: Rate 48000, channels 2, format 2, latency in frames 4800.
```

After some digging, I found the key reason is opensl is incompatible with f32 when minsdk <= LOLLPOP.

From this  [commit](https://hg.mozilla.org/mozilla-central/rev/0a0ec1730ddb#l2.13) (bingo, i guessed right) , Audio output format is  AUDIO_OUTPUT_FORMAT = AUDIO_FORMAT_FLOAT32 ,  will be converted to `CUBEB_SAMPLE_FLOAT32NE` (format 2 in the second line of the log) for cubeb.
```
params.format = CubebUtils::ToCubebFormat<AUDIO_OUTPUT_FORMAT>::value;

template <AudioSampleFormat N>
struct ToCubebFormat {
  static const cubeb_sample_format value = CUBEB_SAMPLE_FLOAT32NE;
};
```

then the keypoint https://searchfox.org/mozilla-central/source/media/libcubeb/src/cubeb_opensl.c#1108-1130

if `__ANDROID_API__` <  ANDROID_VERSION_LOLLIPOP , `opensl_set_format_ext` is not defined and will not be called, so `format` is NULL , then `opensl_set_format` will be called. In `opensl_set_format` , only ` CUBEB_SAMPLE_S16LE` and ` CUBEB_SAMPLE_S16BE` will be handled, other format will cause  CUBEB_ERROR_INVALID_FORMAT. then Audio failed to initialize.

When targetting armeabi  , the `__ANDROID_API__` is 16 (because of --target=arm-linux-androideabi16) < ANDROID_VERSION_LOLLIPOP  (21)  , so failure occurs.

When targetting arm64  , the `__ANDROID_API__` is 21 (because of --target=aarch64-linux-android21) ==  ANDROID_VERSION_LOLLIPOP  (21) , so format is assigned by `opensl_set_format_ext`.


-------------------------
Although i don't know 1) why `opensl` is still used in Android 11.  2)  why ndk targetting to API 16 when building armeabi.

Got anwser for question 2 from geckoview matrix channel. https://searchfox.org/mozilla-central/rev/ce049e593c7d062a039938cabccaab4c14b8ebfd/build/moz.configure/android-ndk.configure#36-41