ac-mobile-android/ndk/jni/opus_bridge.c

/* package ndk/jni/opus_bridge.c */

/*********************************************************************
 * opus_bridge.c
 * Created at: Sun 17 May 2026 22:49:49 +0200
 * Updated at: Sun 28 Jun 2026 22:00:00 +0200 by Anton Afanasyeu <a.afanasieff@gmail.com>
 * Contributors:
 *    - Anton Afanasyeu <a.afanasieff@gmail.com>
 *    - Cursor Agent (project assistant)
 **********************************************************************/
#include <jni.h>
#include <stdlib.h>
#include <string.h>
#include <android/log.h>

#define LOG_TAG "OpusBridge"
#define LOGE(...) __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)
#define LOGI(...) __android_log_print(ANDROID_LOG_INFO,  LOG_TAG, __VA_ARGS__)

#ifndef ANDROIDCAST_HAVE_OPUS
#define ANDROIDCAST_HAVE_OPUS 0
#endif

#if ANDROIDCAST_HAVE_OPUS
#include <opus/opus.h>

#define OPUS_ENC_MAGIC 0x4F505345L /* OPSE */
#define OPUS_DEC_MAGIC 0x4F505344L /* OPSD */

/* Max frame size: 120ms at 48kHz stereo */
#define OPUS_MAX_FRAME_BYTES 4000
#define OPUS_MAX_PCM_SAMPLES 5760

typedef struct {
    unsigned long magic;
    OpusEncoder  *enc;
    int           sample_rate;
    int           channels;
    int           frame_size; /* samples per frame (e.g. 960 = 20ms @ 48 kHz) */
} OpusEncCtx;

typedef struct {
    unsigned long magic;
    OpusDecoder  *dec;
    int           sample_rate;
    int           channels;
    int           frame_size;
} OpusDecCtx;

static OpusEncCtx *enc_from_handle(jlong h) {
    if (h == 0) return NULL;
    OpusEncCtx *ctx = (OpusEncCtx *)(intptr_t)h;
    if (ctx->magic != OPUS_ENC_MAGIC) return NULL;
    return ctx;
}

static OpusDecCtx *dec_from_handle(jlong h) {
    if (h == 0) return NULL;
    OpusDecCtx *ctx = (OpusDecCtx *)(intptr_t)h;
    if (ctx->magic != OPUS_DEC_MAGIC) return NULL;
    return ctx;
}
#endif /* ANDROIDCAST_HAVE_OPUS */

/* ── availability probe ───────────────────────────────────────────── */

JNIEXPORT jboolean JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeIsOpusAvailable(
        JNIEnv *env, jclass clazz) {
    (void)env; (void)clazz;
    return ANDROIDCAST_HAVE_OPUS ? JNI_TRUE : JNI_FALSE;
}

/* ── encoder ────────────────────────────────────────────────────────── */

JNIEXPORT jlong JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusEncoderCreate(
        JNIEnv *env, jclass clazz,
        jint sampleRate, jint channels, jint bitrateKbps) {
    (void)env; (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    int err = OPUS_OK;
    OpusEncoder *enc = opus_encoder_create(sampleRate, channels, OPUS_APPLICATION_VOIP, &err);
    if (err != OPUS_OK || enc == NULL) {
        LOGE("opus_encoder_create failed: %s", opus_strerror(err));
        return 0L;
    }
    int bps = bitrateKbps > 0 ? bitrateKbps * 1000 : OPUS_AUTO;
    opus_encoder_ctl(enc, OPUS_SET_BITRATE(bps));
    opus_encoder_ctl(enc, OPUS_SET_INBAND_FEC(1));
    opus_encoder_ctl(enc, OPUS_SET_DTX(0));
    opus_encoder_ctl(enc, OPUS_SET_COMPLEXITY(5));

    OpusEncCtx *ctx = (OpusEncCtx *)calloc(1, sizeof(OpusEncCtx));
    if (!ctx) { opus_encoder_destroy(enc); return 0L; }
    ctx->magic      = OPUS_ENC_MAGIC;
    ctx->enc        = enc;
    ctx->sample_rate = sampleRate;
    ctx->channels   = channels;
    /* 20 ms frame — e.g. 960 samples @ 48 kHz, 320 @ 16 kHz */
    ctx->frame_size = sampleRate * 20 / 1000;
    LOGI("encoder created sr=%d ch=%d fs=%d bps=%d", sampleRate, channels, ctx->frame_size, bps);
    return (jlong)(intptr_t)ctx;
#else
    (void)sampleRate; (void)channels; (void)bitrateKbps;
    return 0L;
#endif
}

JNIEXPORT jbyteArray JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusEncode(
        JNIEnv *env, jclass clazz,
        jlong handle, jbyteArray pcm16le, jint length) {
    (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    OpusEncCtx *ctx = enc_from_handle(handle);
    if (!ctx || pcm16le == NULL || length <= 0) return NULL;

    jbyte *pcm_bytes = (*env)->GetByteArrayElements(env, pcm16le, NULL);
    if (!pcm_bytes) return NULL;

    const opus_int16 *pcm = (const opus_int16 *)pcm_bytes;
    int samples = length / (2 * ctx->channels); /* bytes → samples per channel */
    if (samples < ctx->frame_size) {
        (*env)->ReleaseByteArrayElements(env, pcm16le, pcm_bytes, JNI_ABORT);
        return NULL;
    }

    unsigned char out_buf[OPUS_MAX_FRAME_BYTES];
    opus_int32 encoded = opus_encode(ctx->enc, pcm, ctx->frame_size, out_buf, sizeof(out_buf));
    (*env)->ReleaseByteArrayElements(env, pcm16le, pcm_bytes, JNI_ABORT);

    if (encoded < 0) {
        LOGE("opus_encode: %s", opus_strerror(encoded));
        return NULL;
    }
    jbyteArray result = (*env)->NewByteArray(env, encoded);
    if (result) {
        (*env)->SetByteArrayRegion(env, result, 0, encoded, (jbyte *)out_buf);
    }
    return result;
#else
    (void)handle; (void)pcm16le; (void)length;
    return NULL;
#endif
}

JNIEXPORT void JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusEncoderRelease(
        JNIEnv *env, jclass clazz, jlong handle) {
    (void)env; (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    OpusEncCtx *ctx = enc_from_handle(handle);
    if (!ctx) return;
    opus_encoder_destroy(ctx->enc);
    ctx->magic = 0;
    free(ctx);
#else
    (void)handle;
#endif
}

JNIEXPORT jint JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusEncoderGetFrameSize(
        JNIEnv *env, jclass clazz, jlong handle) {
    (void)env; (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    OpusEncCtx *ctx = enc_from_handle(handle);
    return ctx ? ctx->frame_size : 0;
#else
    (void)handle; return 0;
#endif
}

/* ── decoder ────────────────────────────────────────────────────────── */

JNIEXPORT jlong JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusDecoderCreate(
        JNIEnv *env, jclass clazz, jint sampleRate, jint channels) {
    (void)env; (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    int err = OPUS_OK;
    OpusDecoder *dec = opus_decoder_create(sampleRate, channels, &err);
    if (err != OPUS_OK || dec == NULL) {
        LOGE("opus_decoder_create failed: %s", opus_strerror(err));
        return 0L;
    }
    OpusDecCtx *ctx = (OpusDecCtx *)calloc(1, sizeof(OpusDecCtx));
    if (!ctx) { opus_decoder_destroy(dec); return 0L; }
    ctx->magic      = OPUS_DEC_MAGIC;
    ctx->dec        = dec;
    ctx->sample_rate = sampleRate;
    ctx->channels   = channels;
    ctx->frame_size = sampleRate * 20 / 1000;
    LOGI("decoder created sr=%d ch=%d", sampleRate, channels);
    return (jlong)(intptr_t)ctx;
#else
    (void)sampleRate; (void)channels;
    return 0L;
#endif
}

JNIEXPORT jbyteArray JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusDecode(
        JNIEnv *env, jclass clazz,
        jlong handle, jbyteArray opus_data, jint length) {
    (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    OpusDecCtx *ctx = dec_from_handle(handle);
    if (!ctx) return NULL;

    jbyte  *in_bytes = NULL;
    int     in_len   = 0;
    if (opus_data != NULL && length > 0) {
        in_bytes = (*env)->GetByteArrayElements(env, opus_data, NULL);
        in_len   = length;
    }

    opus_int16 pcm_buf[OPUS_MAX_PCM_SAMPLES];
    int frames = opus_decode(ctx->dec,
                             in_bytes ? (const unsigned char *)in_bytes : NULL,
                             in_len,
                             pcm_buf, OPUS_MAX_PCM_SAMPLES / ctx->channels, 0);

    if (in_bytes) (*env)->ReleaseByteArrayElements(env, opus_data, in_bytes, JNI_ABORT);

    if (frames < 0) {
        LOGE("opus_decode: %s", opus_strerror(frames));
        return NULL;
    }

    int pcm_bytes = frames * ctx->channels * 2; /* 16-bit PCM */
    jbyteArray result = (*env)->NewByteArray(env, pcm_bytes);
    if (result) {
        (*env)->SetByteArrayRegion(env, result, 0, pcm_bytes, (jbyte *)pcm_buf);
    }
    return result;
#else
    (void)handle; (void)opus_data; (void)length;
    return NULL;
#endif
}

JNIEXPORT void JNICALL
Java_com_foxx_androidcast_media_codec_jni_NativeCodecBridge_nativeOpusDecoderRelease(
        JNIEnv *env, jclass clazz, jlong handle) {
    (void)env; (void)clazz;
#if ANDROIDCAST_HAVE_OPUS
    OpusDecCtx *ctx = dec_from_handle(handle);
    if (!ctx) return;
    opus_decoder_destroy(ctx->dec);
    ctx->magic = 0;
    free(ctx);
#else
    (void)handle;
#endif
}