Function decode_frame

libavcodec/vima.c:121–223

}

static int decode_frame(AVCodecContext *avctx, AVFrame *frame,
                        int *got_frame_ptr, AVPacket *pkt)
{
    GetBitContext gb;
    int16_t pcm_data[2];
    uint32_t samples;
    int8_t channel_hint[2];
    int ret, chan;
    int channels = 1;

    if (pkt->size < 13)
        return AVERROR_INVALIDDATA;

    if ((ret = init_get_bits8(&gb, pkt->data, pkt->size)) < 0)
        return ret;

    samples = get_bits_long(&gb, 32);
    if (samples == 0xffffffff) {
        skip_bits_long(&gb, 32);
        samples = get_bits_long(&gb, 32);
    }

    if (samples > pkt->size * 2)
        return AVERROR_INVALIDDATA;

    channel_hint[0] = get_sbits(&gb, 8);
    if (channel_hint[0] & 0x80) {
        channel_hint[0] = ~channel_hint[0];
        channels = 2;
    }
    av_channel_layout_uninit(&avctx->ch_layout);
    av_channel_layout_default(&avctx->ch_layout, channels);
    pcm_data[0] = get_sbits(&gb, 16);
    if (channels > 1) {
        channel_hint[1] = get_sbits(&gb, 8);
        pcm_data[1]     = get_sbits(&gb, 16);
    }

    frame->nb_samples = samples;
    if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
        return ret;

    if (show_bits_long(&gb, 32) == MKBETAG('I','M','A','4')) {
        int16_t *dest = (int16_t *)frame->data[0];
        ADPCMChannelStatus cs;

        skip_bits_long(&gb, 32);        /* skip the 'IMA4' tag */
        cs.predictor = (int16_t)get_xbits_le(&gb, 16);
        cs.step_index = av_clip(get_bits(&gb, 8), 0, 88);
        for (int i = 0; i < samples; i++) {
            ff_adpcm_ima_qt_expand_nibble(&cs, get_bits(&gb, 4));
            for (int j = 0; j < channels; j++)
                *dest++ = cs.predictor;
        }
    } else {
        for (chan = 0; chan < channels; chan++) {
            uint16_t *dest = (uint16_t *)frame->data[0] + chan;
            int step_index = channel_hint[chan];