Example #1
0
/** @internal @This is called to consume frames out of the first buffered uref.
 *
 * @param upipe description structure of the pipe
 * @param frames number of frames to consume
 */
static void upipe_nacl_audio_consume(struct upipe *upipe, uint32_t frames)
{
    struct upipe_nacl_audio *upipe_nacl_audio =
        upipe_nacl_audio_from_upipe(upipe);
    struct uref *uref = upipe_nacl_audio->uref;
    assert(uref != NULL);

    size_t uref_size;
    if (ubase_check(uref_sound_size(uref, &uref_size, NULL)) &&
        uref_size <= frames) {
        upipe_nacl_audio->uref = NULL;
        uref_free(uref);
    } else {
        uref_sound_resize(uref, frames, -1);
        uint64_t pts;
        if (ubase_check(uref_clock_get_pts_sys(uref, &pts)))
            uref_clock_set_pts_sys(uref,
                    pts + frames * UCLOCK_FREQ / SAMPLE_RATE);
        /* We should also change the duration but we don't use it. */
    }
}
Example #2
0
/** @internal @This handles input.
 *
 * @param upipe description structure of the pipe
 * @param uref uref structure
 * @param upump_p reference to upump structure
 */
static void upipe_filter_ebur128_input(struct upipe *upipe, struct uref *uref,
                                       struct upump **upump_p)
{
    struct upipe_filter_ebur128 *upipe_filter_ebur128 =
                                 upipe_filter_ebur128_from_upipe(upipe);
    double loud = 0, lra = 0, global = 0;
    size_t samples;
    if (unlikely(!ubase_check(uref_sound_size(uref, &samples, NULL)))) {
        upipe_warn(upipe, "invalid sound buffer");
        uref_free(uref);
        return;
    }
    const char *channel = NULL;
    const int16_t *buf = NULL;
    if (ubase_check(uref_sound_plane_iterate(uref, &channel)) && channel) {
        if (unlikely(!ubase_check(uref_sound_plane_read_int16_t(uref,
                channel, 0, -1, &buf)))) {
            upipe_warn(upipe, "error mapping sound buffer");
            uref_free(uref);
            return;
        }

        if (unlikely((uintptr_t)buf & 1)) {
            upipe_warn(upipe, "unaligned buffer");
        }
        ebur128_add_frames_short(upipe_filter_ebur128->st, buf, samples);
        uref_sound_plane_unmap(uref, channel, 0, -1);
    }
    ebur128_loudness_momentary(upipe_filter_ebur128->st, &loud);
    ebur128_loudness_range(upipe_filter_ebur128->st, &lra);
    ebur128_loudness_global(upipe_filter_ebur128->st, &global);

    uref_ebur128_set_momentary(uref, loud);
    uref_ebur128_set_lra(uref, lra);
    uref_ebur128_set_global(uref, global);

    upipe_verbose_va(upipe, "loud %f lra %f global %f", loud, lra, global);

    upipe_filter_ebur128_output(upipe, uref, upump_p);
}
Example #3
0
/** @internal @This inputs data.
 *
 * @param upipe description structure of the pipe
 * @param uref uref structure
 * @param upump_p reference to upump structure
 */
static void upipe_nacl_audio_input(struct upipe *upipe, struct uref *uref, 
                                   struct upump **upump_p)
{    
    struct upipe_nacl_audio *upipe_nacl_audio =
        upipe_nacl_audio_from_upipe(upipe);
    size_t uref_size;
    if (unlikely(!ubase_check(uref_sound_size(uref, &uref_size, NULL)))) {
        upipe_warn(upipe, "unable to read uref");
        uref_free(uref);
        return;
    }

    if (unlikely(!upipe_nacl_audio->started && !upipe_nacl_audio_open(upipe))) {
        upipe_warn(upipe, "unable to open device");
        uref_free(uref);
        return;
    }

    uint64_t uref_pts;
    if (likely(ubase_check(uref_clock_get_pts_sys(uref, &uref_pts)))) {
        uref_pts += upipe_nacl_audio->latency;
        uref_clock_set_pts_sys(uref, uref_pts);
    }

    if (!upipe_nacl_audio_check_input(upipe)) {
        upipe_nacl_audio_hold_input(upipe, uref);
        upipe_nacl_audio_block_input(upipe, upump_p);
    } else if (!upipe_nacl_audio_handle(upipe, uref, upump_p)) {
        if (!upipe_nacl_audio_check_watcher(upipe)) {
            upipe_warn(upipe, "unable to spool uref");
            uref_free(uref);
            return;
        }
        upipe_nacl_audio_hold_input(upipe, uref);
        upipe_nacl_audio_block_input(upipe, upump_p);
        upump_start(upipe_nacl_audio->upump);
    }
}
Example #4
0
/** @internal @This handles input.
 *
 * @param upipe description structure of the pipe
 * @param uref uref structure
 * @param upump_p reference to upump structure
 */
static void upipe_filter_ebur128_input(struct upipe *upipe, struct uref *uref,
                                       struct upump **upump_p)
{
    struct upipe_filter_ebur128 *upipe_filter_ebur128 =
                                 upipe_filter_ebur128_from_upipe(upipe);
    double loud = 0, lra = 0, global = 0;

    if (unlikely(upipe_filter_ebur128->output_flow == NULL)) {
        upipe_err_va(upipe, "invalid input");
        uref_free(uref);
        return;
    }

    size_t samples;
    uint8_t sample_size;
    if (unlikely(!ubase_check(uref_sound_size(uref, &samples, &sample_size)))) {
        upipe_warn(upipe, "invalid sound buffer");
        uref_free(uref);
        return;
    }

    void *buf = NULL;
    const char *channel = NULL;
    if (upipe_filter_ebur128->planes == 1) {
        if (ubase_check(uref_sound_plane_iterate(uref, &channel)) && channel) {
            if (unlikely(!ubase_check(uref_sound_plane_read_void(uref,
                    channel, 0, -1, (const void **)&buf)))) {
                upipe_warn(upipe, "error mapping sound buffer");
                uref_free(uref);
                return;
            }
        }

    } else {
        buf = malloc(sample_size * upipe_filter_ebur128->channels * samples);
        if (buf == NULL) {
            upipe_throw_fatal(upipe, UBASE_ERR_ALLOC);
            uref_free(uref);
            return;
        }
        if (!ubase_check(uref_sound_interleave(uref, (uint8_t *)buf, 0,
                                               samples, sample_size,
                                               upipe_filter_ebur128->planes))) {
            upipe_warn(upipe, "error mapping sound buffer");
            uref_free(uref);
            return;
        }
    }

    if (unlikely((uintptr_t)buf & 1))
        upipe_warn(upipe, "unaligned buffer");

    switch (upipe_filter_ebur128->fmt) {
        case UPIPE_FILTER_EBUR128_SHORT:
            ebur128_add_frames_short(upipe_filter_ebur128->st, (short *)buf,
                                     samples);
            break;

        case UPIPE_FILTER_EBUR128_INT:
            ebur128_add_frames_int(upipe_filter_ebur128->st, (int *)buf,
                                   samples);
            break;

        case UPIPE_FILTER_EBUR128_FLOAT:
            ebur128_add_frames_float(upipe_filter_ebur128->st, (float *)buf,
                                     samples);
            break;

        case UPIPE_FILTER_EBUR128_DOUBLE:
            ebur128_add_frames_double(upipe_filter_ebur128->st, (double *)buf,
                                      samples);
            break;

        default:
            upipe_warn_va(upipe, "unknown sample format %d",
                          upipe_filter_ebur128->fmt);
            break;
    }

    if (upipe_filter_ebur128->planes == 1)
        uref_sound_plane_unmap(uref, channel, 0, -1);
    else
        free(buf);

    ebur128_loudness_momentary(upipe_filter_ebur128->st, &loud);
    ebur128_loudness_range(upipe_filter_ebur128->st, &lra);
    ebur128_loudness_global(upipe_filter_ebur128->st, &global);

    uref_ebur128_set_momentary(uref, loud);
    uref_ebur128_set_lra(uref, lra);
    uref_ebur128_set_global(uref, global);

    upipe_verbose_va(upipe, "loud %f lra %f global %f", loud, lra, global);

    upipe_filter_ebur128_output(upipe, uref, upump_p);
}
Example #5
0
/** @internal @This handles data from sound allocator.
 *
 * @param upipe description structure of the pipe
 * @param uref uref structure
 * @param upump_p reference to pump that generated the buffer
 */
static void upipe_tblk_handle_sound(struct upipe *upipe, struct uref *uref,
                                    struct upump **upump_p)
{
    struct upipe_tblk *upipe_tblk = upipe_tblk_from_upipe(upipe);

    /* Always operate on the first channel plane. */
    const char *channel = NULL;
    if (unlikely(uref->ubuf == NULL ||
                 !ubase_check(ubuf_sound_plane_iterate(uref->ubuf, &channel)) ||
                 channel == NULL)) {
        uref_free(uref);
        upipe_throw_error(upipe, UBASE_ERR_INVALID);
        return;
    }

    /* First try the ubuf_mem_shared method. */
    struct ubuf *ubuf = ubuf_block_mem_alloc_from_sound(upipe_tblk->ubuf_mgr,
                                                        uref->ubuf, channel);
    if (unlikely(ubuf == NULL)) {
        /* We have to memcpy the thing. */
        size_t samples;
        uint8_t sample_size;
        if (unlikely(!ubase_check(uref_sound_size(uref, &samples,
                                                  &sample_size)))) {
            uref_free(uref);
            upipe_throw_error(upipe, UBASE_ERR_INVALID);
            return;
        }

        size_t size = samples * sample_size;
        ubuf = ubuf_block_alloc(upipe_tblk->ubuf_mgr, size);
        if (unlikely(ubuf == NULL)) {
            uref_free(uref);
            upipe_throw_error(upipe, UBASE_ERR_ALLOC);
            return;
        }

        const uint8_t *r;
        if (unlikely(!ubase_check(uref_sound_plane_read_uint8_t(uref, channel,
                                                                0, -1, &r)))) {
            ubuf_free(ubuf);
            uref_free(uref);
            upipe_throw_error(upipe, UBASE_ERR_ALLOC);
            return;
        }

        uint8_t *w;
        int end = -1;
        if (unlikely(!ubase_check(ubuf_block_write(ubuf, 0, &end, &w)))) {
            uref_sound_plane_unmap(uref, channel, 0, -1);
            ubuf_free(ubuf);
            uref_free(uref);
            upipe_throw_error(upipe, UBASE_ERR_ALLOC);
            return;
        }

        memcpy(w, r, size);
        ubuf_block_unmap(ubuf, 0);
        uref_sound_plane_unmap(uref, channel, 0, -1);
    }

    uref_attach_ubuf(uref, ubuf);
    upipe_tblk_output(upipe, uref, upump_p);
}
Example #6
0
/** @internal @This handles data.
 *
 * @param upipe description structure of the pipe
 * @param uref uref structure
 * @param upump_p reference to pump that generated the buffer
 * @return false if the input must be blocked
 */
static bool upipe_speexdsp_handle(struct upipe *upipe, struct uref *uref,
                             struct upump **upump_p)
{
    struct upipe_speexdsp *upipe_speexdsp = upipe_speexdsp_from_upipe(upipe);

    struct urational drift_rate;
    if (!ubase_check(uref_clock_get_rate(uref, &drift_rate)))
        drift_rate = (struct urational){ 1, 1 };

    /* reinitialize resampler when drift rate changes */
    if (urational_cmp(&drift_rate, &upipe_speexdsp->drift_rate)) {
        upipe_speexdsp->drift_rate = drift_rate;
        spx_uint32_t ratio_num = drift_rate.den;
        spx_uint32_t ratio_den = drift_rate.num;
        spx_uint32_t in_rate = upipe_speexdsp->rate * ratio_num / ratio_den;
        spx_uint32_t out_rate = upipe_speexdsp->rate;
        int err = speex_resampler_set_rate_frac(upipe_speexdsp->ctx,
                ratio_num, ratio_den, in_rate, out_rate);
        if (err) {
            upipe_err_va(upipe, "Couldn't resample from %u to %u: %s",
                in_rate, out_rate, speex_resampler_strerror(err));
        } else {
            upipe_dbg_va(upipe, "Resampling from %u to %u",
                in_rate, out_rate);
        }
    }

    size_t size;
    if (!ubase_check(uref_sound_size(uref, &size, NULL /* sample_size */))) {
        uref_free(uref);
        return true;
    }

    struct ubuf *ubuf = ubuf_sound_alloc(upipe_speexdsp->ubuf_mgr, size + 10);
    if (!ubuf)
        return false;

    const void *in;
    uref_sound_read_void(uref, 0, -1, &in, 1);

    void *out;
    ubuf_sound_write_void(ubuf, 0, -1, &out, 1);

    spx_uint32_t in_len = size;         /* input size */
    spx_uint32_t out_len = size + 10;   /* available output size */

    int err;

    if (upipe_speexdsp->f32)
        err = speex_resampler_process_interleaved_float(upipe_speexdsp->ctx,
                in, &in_len, out, &out_len);
    else
        err = speex_resampler_process_interleaved_int(upipe_speexdsp->ctx,
                in, &in_len, out, &out_len);

    if (err) {
        upipe_err_va(upipe, "Could not resample: %s",
                speex_resampler_strerror(err));
    }

    uref_sound_unmap(uref, 0, -1, 1);
    ubuf_sound_unmap(ubuf, 0, -1, 1);

    if (err) {
        ubuf_free(ubuf);
    } else {
        ubuf_sound_resize(ubuf, 0, out_len);
        uref_attach_ubuf(uref, ubuf);
    }

    upipe_speexdsp_output(upipe, uref, upump_p);
    return true;
}

/** @internal @This receives incoming uref.
 *
 * @param upipe description structure of the pipe
 * @param uref uref structure describing the picture
 * @param upump_p reference to pump that generated the buffer
 */
static void upipe_speexdsp_input(struct upipe *upipe, struct uref *uref,
                            struct upump **upump_p)
{
    if (!upipe_speexdsp_check_input(upipe)) {
        upipe_speexdsp_hold_input(upipe, uref);
        upipe_speexdsp_block_input(upipe, upump_p);
    } else if (!upipe_speexdsp_handle(upipe, uref, upump_p)) {
        upipe_speexdsp_hold_input(upipe, uref);
        upipe_speexdsp_block_input(upipe, upump_p);
        /* Increment upipe refcount to avoid disappearing before all packets
         * have been sent. */
        upipe_use(upipe);
    }
}

/** @internal @This receives a provided ubuf manager.
 *
 * @param upipe description structure of the pipe
 * @param flow_format amended flow format
 * @return an error code
 */
static int upipe_speexdsp_check(struct upipe *upipe, struct uref *flow_format)
{
    struct upipe_speexdsp *upipe_speexdsp = upipe_speexdsp_from_upipe(upipe);
    if (flow_format != NULL)
        upipe_speexdsp_store_flow_def(upipe, flow_format);

    if (upipe_speexdsp->flow_def == NULL)
        return UBASE_ERR_NONE;

    bool was_buffered = !upipe_speexdsp_check_input(upipe);
    upipe_speexdsp_output_input(upipe);
    upipe_speexdsp_unblock_input(upipe);
    if (was_buffered && upipe_speexdsp_check_input(upipe)) {
        /* All packets have been output, release again the pipe that has been
         * used in @ref upipe_speexdsp_input. */
        upipe_release(upipe);
    }
    return UBASE_ERR_NONE;
}

/** @internal @This sets the input flow definition.
 *
 * @param upipe description structure of the pipe
 * @param flow_def flow definition packet
 * @return an error code
 */
static int upipe_speexdsp_set_flow_def(struct upipe *upipe, struct uref *flow_def)
{
    struct upipe_speexdsp *upipe_speexdsp = upipe_speexdsp_from_upipe(upipe);

    if (flow_def == NULL)
        return UBASE_ERR_INVALID;

    const char *def;
    UBASE_RETURN(uref_flow_get_def(flow_def, &def))

    if (unlikely(ubase_ncmp(def, "sound.f32.") &&
                ubase_ncmp(def, "sound.s16.")))
        return UBASE_ERR_INVALID;

    uint8_t in_planes;
    if (unlikely(!ubase_check(uref_sound_flow_get_planes(flow_def,
                                                         &in_planes))))
        return UBASE_ERR_INVALID;

    if (in_planes != 1) {
        upipe_err(upipe, "only interleaved audio is supported");
        return UBASE_ERR_INVALID;
    }

    if (!ubase_check(uref_sound_flow_get_rate(flow_def,
                    &upipe_speexdsp->rate))) {
        upipe_err(upipe, "no sound rate defined");
        uref_dump(flow_def, upipe->uprobe);
        return UBASE_ERR_INVALID;
    }

    uint8_t channels;
    if (unlikely(!ubase_check(uref_sound_flow_get_channels(flow_def,
                        &channels))))
        return UBASE_ERR_INVALID;

    flow_def = uref_dup(flow_def);
    if (unlikely(flow_def == NULL)) {
        upipe_throw_fatal(upipe, UBASE_ERR_ALLOC);
        return UBASE_ERR_ALLOC;
    }

    upipe_speexdsp_require_ubuf_mgr(upipe, flow_def);

    if (upipe_speexdsp->ctx)
        speex_resampler_destroy(upipe_speexdsp->ctx);

    upipe_speexdsp->f32 = !ubase_ncmp(def, "sound.f32.");

    int err;
    upipe_speexdsp->ctx = speex_resampler_init(channels,
                upipe_speexdsp->rate, upipe_speexdsp->rate,
                upipe_speexdsp->quality, &err);
    if (!upipe_speexdsp->ctx) {
        upipe_err_va(upipe, "Could not create resampler: %s",
                speex_resampler_strerror(err));
        return UBASE_ERR_INVALID;
    }

    return UBASE_ERR_NONE;
}

/** @internal @This provides a flow format suggestion.
 *
 * @param upipe description structure of the pipe
 * @param request description structure of the request
 * @return an error code
 */
static int upipe_speexdsp_provide_flow_format(struct upipe *upipe,
                                          struct urequest *request)
{
    const char *def;
    UBASE_RETURN(uref_flow_get_def(request->uref, &def))
    uint8_t channels;
    UBASE_RETURN(uref_sound_flow_get_channels(request->uref, &channels))
    uint8_t planes;
    UBASE_RETURN(uref_sound_flow_get_planes(request->uref, &planes))
    uint8_t sample_size;
    UBASE_RETURN(uref_sound_flow_get_sample_size(request->uref, &sample_size))

    struct uref *flow = uref_dup(request->uref);
    UBASE_ALLOC_RETURN(flow);

    uref_sound_flow_clear_format(flow);
    uref_sound_flow_set_planes(flow, 0);
    uref_sound_flow_set_channels(flow, channels);
    uref_sound_flow_add_plane(flow, "all");
    if (ubase_ncmp(def, "sound.s16.")) {
        uref_flow_set_def(flow, "sound.f32."); /* prefer f32 over s16 */
        uref_sound_flow_set_sample_size(flow, 4 * channels);
    } else {
        uref_flow_set_def(flow, def);
        uref_sound_flow_set_sample_size(flow, (planes > 1) ? sample_size :
                sample_size / channels);
    }

    return urequest_provide_flow_format(request, flow);
}

/** @internal @This processes control commands on a speexdsp pipe.
 *
 * @param upipe description structure of the pipe
 * @param command type of command to process
 * @param args arguments of the command
 * @return an error code
 */
static int upipe_speexdsp_control(struct upipe *upipe, int command, va_list args)
{
    struct upipe_speexdsp *upipe_speexdsp = upipe_speexdsp_from_upipe(upipe);

    switch (command) {
        /* generic commands */
        case UPIPE_REGISTER_REQUEST: {
            struct urequest *request = va_arg(args, struct urequest *);
            if (request->type == UREQUEST_FLOW_FORMAT)
                return upipe_speexdsp_provide_flow_format(upipe, request);
            if (request->type == UREQUEST_UBUF_MGR)
                return upipe_throw_provide_request(upipe, request);
            return upipe_speexdsp_alloc_output_proxy(upipe, request);
        }
        case UPIPE_UNREGISTER_REQUEST: {
            struct urequest *request = va_arg(args, struct urequest *);
            if (request->type == UREQUEST_FLOW_FORMAT ||
                request->type == UREQUEST_UBUF_MGR)
                return UBASE_ERR_NONE;
            return upipe_speexdsp_free_output_proxy(upipe, request);
        }

        case UPIPE_GET_OUTPUT: {
            struct upipe **p = va_arg(args, struct upipe **);
            return upipe_speexdsp_get_output(upipe, p);
        }
        case UPIPE_SET_OUTPUT: {
            struct upipe *output = va_arg(args, struct upipe *);
            return upipe_speexdsp_set_output(upipe, output);
        }
        case UPIPE_GET_FLOW_DEF: {
            struct uref **p = va_arg(args, struct uref **);
            return upipe_speexdsp_get_flow_def(upipe, p);
        }
        case UPIPE_SET_FLOW_DEF: {
            struct uref *flow = va_arg(args, struct uref *);
            return upipe_speexdsp_set_flow_def(upipe, flow);
        }
        case UPIPE_SET_OPTION: {
            const char *option = va_arg(args, const char *);
            const char *value  = va_arg(args, const char *);
            if (strcmp(option, "quality"))
                return UBASE_ERR_INVALID;
            if (upipe_speexdsp->ctx)
                return UBASE_ERR_BUSY;
            int quality = atoi(value);
            if (quality > SPEEX_RESAMPLER_QUALITY_MAX) {
                quality = SPEEX_RESAMPLER_QUALITY_MAX;
                upipe_err_va(upipe, "Clamping quality to %d",
                        SPEEX_RESAMPLER_QUALITY_MAX);
            } else if (quality < SPEEX_RESAMPLER_QUALITY_MIN) {
                quality = SPEEX_RESAMPLER_QUALITY_MIN;
                upipe_err_va(upipe, "Clamping quality to %d",
                        SPEEX_RESAMPLER_QUALITY_MIN);
            }
            upipe_speexdsp->quality = quality;
            return UBASE_ERR_NONE;
        }

        default:
            return UBASE_ERR_UNHANDLED;
    }
}

/** @internal @This allocates a speexdsp pipe.
 *
 * @param mgr common management structure
 * @param uprobe structure used to raise events
 * @param signature signature of the pipe allocator
 * @param args optional arguments
 * @return pointer to upipe or NULL in case of allocation error
 */
static struct upipe *upipe_speexdsp_alloc(struct upipe_mgr *mgr,
                                     struct uprobe *uprobe,
                                     uint32_t signature, va_list args)
{
    struct upipe *upipe = upipe_speexdsp_alloc_void(mgr, uprobe, signature,
                                               args);
    if (unlikely(upipe == NULL))
        return NULL;

    struct upipe_speexdsp *upipe_speexdsp = upipe_speexdsp_from_upipe(upipe);

    upipe_speexdsp->ctx = NULL;
    upipe_speexdsp->drift_rate = (struct urational){ 0, 0 };
    upipe_speexdsp->quality = SPEEX_RESAMPLER_QUALITY_MAX;

    upipe_speexdsp_init_urefcount(upipe);
    upipe_speexdsp_init_ubuf_mgr(upipe);
    upipe_speexdsp_init_output(upipe);
    upipe_speexdsp_init_flow_def(upipe);
    upipe_speexdsp_init_input(upipe);

    upipe_throw_ready(upipe);
    return upipe;
}

/** @This frees a upipe.
 *
 * @param upipe description structure of the pipe
 */
static void upipe_speexdsp_free(struct upipe *upipe)
{
    struct upipe_speexdsp *upipe_speexdsp = upipe_speexdsp_from_upipe(upipe);
    if (likely(upipe_speexdsp->ctx))
        speex_resampler_destroy(upipe_speexdsp->ctx);

    upipe_throw_dead(upipe);
    upipe_speexdsp_clean_input(upipe);
    upipe_speexdsp_clean_output(upipe);
    upipe_speexdsp_clean_flow_def(upipe);
    upipe_speexdsp_clean_ubuf_mgr(upipe);
    upipe_speexdsp_clean_urefcount(upipe);
    upipe_speexdsp_free_void(upipe);
}

/** module manager static descriptor */
static struct upipe_mgr upipe_speexdsp_mgr = {
    .refcount = NULL,
    .signature = UPIPE_SPEEXDSP_SIGNATURE,

    .upipe_alloc = upipe_speexdsp_alloc,
    .upipe_input = upipe_speexdsp_input,
    .upipe_control = upipe_speexdsp_control,

    .upipe_mgr_control = NULL
};

/** @This returns the management structure for speexdsp pipes
 *
 * @return pointer to manager
 */
struct upipe_mgr *upipe_speexdsp_mgr_alloc(void)
{
    return &upipe_speexdsp_mgr;
}
Example #7
0
/** @internal @This is called back to fill NaCl audio buffer.
 * Please note that this function runs in a different thread.
 *
 * @param sample_buffer buffer to fill
 * @param buffer_size size of the buffer in octets
 * @param latency how long before the audio data is to be presented
 * @param user_data opaque pointing to the pipe
 */
static void upipe_nacl_audio_worker(void *sample_buffer, uint32_t buffer_size,
                                    PP_TimeDelta latency, void *user_data)
{
    struct upipe *upipe = (struct upipe *)user_data;
    struct upipe_nacl_audio *upipe_nacl_audio =
        upipe_nacl_audio_from_upipe(upipe);
    uint64_t next_pts = UINT64_MAX;

    if (likely(upipe_nacl_audio->uclock != NULL)) {
        /* This is slightly off. */
        next_pts = uclock_now(upipe_nacl_audio->uclock) +
                   (uint64_t)(latency * UCLOCK_FREQ);
    }

    uint32_t frames = buffer_size / 4;

    while (frames > 0) {
        if (upipe_nacl_audio->uref == NULL)
            upipe_nacl_audio->uref = uqueue_pop(&upipe_nacl_audio->uqueue,
                                                struct uref *);
        if (unlikely(upipe_nacl_audio->uref == NULL)) {
            upipe_dbg_va(upipe, "playing %u frames of silence (empty)", frames);
            memset(sample_buffer, 0, frames * 4);
            break;
        }

        struct uref *uref = upipe_nacl_audio->uref;
        if (next_pts != UINT64_MAX) {
            uint64_t uref_pts;
            if (unlikely(!ubase_check(uref_clock_get_pts_sys(uref,
                                &uref_pts)))) {
                upipe_nacl_audio->uref = NULL;
                uref_free(uref);
                upipe_warn(upipe, "non-dated uref received");
                continue;
            }

            int64_t tolerance = uref_pts - next_pts;
            if (tolerance > (int64_t)PTS_TOLERANCE) {
                uint32_t silence_frames =
                    tolerance * SAMPLE_RATE / UCLOCK_FREQ;
                if (silence_frames > frames)
                    silence_frames = frames;
                upipe_dbg_va(upipe, "playing %u frames of silence (wait)",
                             silence_frames);
                memset(sample_buffer, 0, silence_frames * 4);
                sample_buffer += silence_frames * 4;
                frames -= silence_frames;
                continue;
            } else if (-tolerance > (int64_t)PTS_TOLERANCE) {
                uint32_t dropped_frames =
                    (-tolerance) * SAMPLE_RATE / UCLOCK_FREQ;
                upipe_warn_va(upipe, "late buffer received, dropping %u frames",
                              dropped_frames);
                upipe_nacl_audio_consume(upipe, dropped_frames);
                continue;
            }
        }

        size_t size;
        const void *uref_buffer;
        if (unlikely(!ubase_check(uref_sound_size(uref, &size, NULL)) ||
                     !ubase_check(uref_sound_plane_read_void(uref, "lr", 0, -1,
                                                             &uref_buffer)))) {
            upipe_nacl_audio->uref = NULL;
            uref_free(uref);
            upipe_warn(upipe, "cannot read ubuf buffer");
            continue;
        }

        uint32_t copied_frames = size < frames ? size : frames;
        memcpy(sample_buffer, uref_buffer, copied_frames * 4);
        uref_sound_plane_unmap(uref, "lr", 0, -1);
        sample_buffer += copied_frames * 4;

        upipe_nacl_audio_consume(upipe, copied_frames);
        frames -= copied_frames;
    }
}