[Feature Request] Termux support

[Bsd-us]

Hello, this issue follows the discussion someone created a few days ago here

As this gave me hope this could be a feature in future builds
All the following was found on Termux's discord and in a dedicated thread you can find here

So audio-file-to-fingerprint and audio-file-to-recognized-song commands ended up working by forcing the build with these obscure commands

pkg install openssh build-essential rust
pkg upgrade
pkg remove ndk-multilib # if you have this, it will somehow conflict
pkg install gettext
export GETTEXT_DIR="$PREFIX"
# this part is hard to explain but basically it compiles the libintl.h into a libintl.a that -lintl works on
sed -e 's/__inline__//g' -e 's/^static//g' $PREFIX/include/libintl.h | clang -O0 -x c -c -o libintl.o -
ar cru $PREFIX/lib/libintl.a libintl.o 
# force -lc++_static to link to libc++_shared.so instead (oboe-sys problem)
echo 'INPUT(-lc++_shared)' > $PREFIX/lib/libc++_static.so
cargo install songrec --no-default-features

As it seems they're mainly the ones which are able to avoid using the audio part of the program
I hope you can check all the details on discord as they're probably very valuable information
thank you for your time !

[robertkirkman]

I am able to see a slightly different log by trying these additional commands as well:

pulseaudio -L module-sles-source -D --exit-idle-time=-1
cargo install songrec --no-default-features --features "pulse"
export RUST_BACKTRACE=1
songrec microphone-to-recognized-song

Using device OpenSL_ES_source

thread '<unnamed>' panicked at /data/data/com.termux/files/home/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/ndk-context-0.1.1/src/lib.rs:72:30:
android context was not initialized
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::option::expect_failed
   3: ndk_context::android_context
   4: cpal::host::oboe::android_media::get_min_buffer_size
   5: cpal::host::oboe::default_supported_configs
   6: <cpal::host::oboe::Device as cpal::traits::DeviceTrait>::default_input_config
   7: songrec::core::microphone_thread::microphone_thread
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

The problem, unfortunately, most likely has to do with the cpal crate

Even though Termux is a port of Pulseaudio, Portaudio, JACK, and OpenAL to Android 7+, and any of these four audio APIs typically associated with "desktop linux", as well as the direct OpenSL ES API of Android 7 that they are implemented on top of in Termux, are simple and easy to use from C and C++ programs in Termux,

in my experience, the cpal crate, commonly used by Rust programs, is currently very difficult to use in Termux because the creators of the cpal crate focus development on providing compatibility with the greater 95% of typical Android apps, devices, developers, tools and use cases, not with the 5% minority of old devices, edge cases, atypical use cases or nonstandard tools, which is completely understandable, because the cpal crate has the task of abstracting as many platform-specific audio APIs as possible into a single unified Rust layer that can be imported by Rust programs, which is not at all easy and which they must spend a great deal of time maintaining to make sure that support for all of the standard, typical use-cases is preserved on all their supported targets

• Migrate from "oboe" to "ndk::audio" RustAudio/cpal#961

One of the reasons is because the minimum target Android API level of the cpal crate is 26 (Android 8+), because the Android-compatible backend of cpal is implemented using AAudio and not OpenSL ES. Since the minimum target Android API level of Termux is 24 (Android 7+), all Termux audio functionality can basically only be implemented on top of OpenSL ES (or one of the four other audio APIs I mentioned above that are themselves ported to OpenSL ES by Termux).

I believe that in order for the cpal crate to be successfully usable inside Termux, probably the easiest way would be to figure out how to force the Android target of the cpal crate to deactivate its AAudio backend and instead activate cpal's JACK backend, after verifying that the JACK server of Termux is functional in most Android devices. Then, all cpal-based Rust programs could be relatively easily set into an alternative mode where they are directed to use the forked/patched custom cpal crate that activates its JACK backend on Android, instead of the AAudio backend.

However, I did try to do that several times in the past and I haven't yet been able to achieve that. The most I have been able to achieve so far in Rust programs inside Termux is to compile them and run them without any functioning microphone or speaker access, like the SongRec example that has been posted here.