Function imc_decode_init

libavcodec/imc.c:188–253

}

static av_cold int imc_decode_init(AVCodecContext *avctx)
{
    int i, j, ret;
    IMCContext *q = avctx->priv_data;
    static AVOnce init_static_once = AV_ONCE_INIT;
    float scale = 1.0f / (16384);

    if (avctx->codec_id == AV_CODEC_ID_IAC && avctx->sample_rate > 96000) {
        av_log(avctx, AV_LOG_ERROR,
               "Strange sample rate of %i, file likely corrupt or "
               "needing a new table derivation method.\n",
               avctx->sample_rate);
        return AVERROR_PATCHWELCOME;
    }

    if (avctx->codec_id == AV_CODEC_ID_IMC) {
        av_channel_layout_uninit(&avctx->ch_layout);
        avctx->ch_layout = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
    }

    if (avctx->ch_layout.nb_channels > 2) {
        avpriv_request_sample(avctx, "Number of channels > 2");
        return AVERROR_PATCHWELCOME;
    }

    for (j = 0; j < avctx->ch_layout.nb_channels; j++) {
        q->chctx[j].decoder_reset = 1;

        for (i = 0; i < BANDS; i++)
            q->chctx[j].old_floor[i] = 1.0;
    }

    /* Build mdct window, a simple sine window normalized with sqrt(2) */
    ff_sine_window_init(q->mdct_sine_window, COEFFS);
    for (i = 0; i < COEFFS; i++)
        q->mdct_sine_window[i] *= sqrt(2.0);

    /* Generate a square root table */
    for (i = 0; i < 30; i++)
        q->sqrt_tab[i] = sqrt(i);

    if (avctx->codec_id == AV_CODEC_ID_IAC) {
        iac_generate_tabs(q, avctx->sample_rate);
    } else {
        memcpy(q->cyclTab,  cyclTab,  sizeof(cyclTab));
        memcpy(q->cyclTab2, cyclTab2, sizeof(cyclTab2));
        memcpy(q->weights1, imc_weights1, sizeof(imc_weights1));
        memcpy(q->weights2, imc_weights2, sizeof(imc_weights2));
    }

    q->fdsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
    if (!q->fdsp)
        return AVERROR(ENOMEM);

    ret = av_tx_init(&q->mdct, &q->mdct_fn, AV_TX_FLOAT_MDCT, 1, COEFFS, &scale, 0);
    if (ret < 0)
        return ret;