[FFmpeg-devel] [PATCH] G.722 decoder

[Martin Storsjö]

On Wed, 8 Sep 2010, Michael Niedermayer wrote:

> On Wed, Sep 08, 2010 at 06:06:42PM +0300, Martin Storsj? wrote:
> [...]
> > +static int g722_decode_frame(AVCodecContext *avctx, void *data,
> > +                             int *data_size, AVPacket *avpkt)
> > +{
> > +    G722Context *c = avctx->priv_data;
> > +    int16_t *out_buf = data;
> > +    int j, out_len = 0;
> > +    const int skip = 8 - avctx->bits_per_coded_sample;
> > +    const int16_t *quantizer_table = low_inv_quants[skip];
> > +    GetBitContext gb;
> > +
> > +    init_get_bits(&gb, avpkt->data, avpkt->size * 8);
> > +
> > +    for (j = 0; j < avpkt->size; j++) {
> > +        int ilow, ihigh, rlow;
> > +        int dhigh, rhigh;
> > +        int xout1, xout2;
> > +
> > +        ihigh = get_bits(&gb, 2);
> > +        ilow = get_bits(&gb, 6 - skip);
> > +        skip_bits(&gb, skip);
> > +
> > +        rlow = av_clip((c->band[0].scale_factor * quantizer_table[ilow] >> 10)
> > +                      + c->band[0].s_predictor, -16384, 16383);
> > +        update_low_predictor(&c->band[0], ilow >> (2 - skip));
> > +
> > +        dhigh = c->band[1].scale_factor * high_inv_quant[ihigh] >> 10;
> > +        rhigh = av_clip(dhigh + c->band[1].s_predictor, -16384, 16383);
> > +        update_high_predictor(&c->band[1], dhigh, ihigh);
> > +
> > +        c->prev_samples[c->prev_samples_pos++] = rlow + rhigh;
> > +        c->prev_samples[c->prev_samples_pos++] = rlow - rhigh;
> > +        apply_qmf(c->prev_samples + c->prev_samples_pos - 24,
> > +                  &xout1, &xout2);
> > +        out_buf[out_len++] = av_clip_int16(xout1 >> 12);
> > +        out_buf[out_len++] = av_clip_int16(xout2 >> 12);
> > +        if (c->prev_samples_pos >= PREV_SAMPLES_BUF_SIZE) {
> > +            memmove(c->prev_samples,
> > +                    c->prev_samples + c->prev_samples_pos - 22,
> > +                    22 * sizeof(c->prev_samples[0]));
> > +            c->prev_samples_pos = 22;
> > +        }
> 
> lowres could be checked for this

Ah, so if avctx->lowres == 1, we'd just output the lower subband? Good 
idea, I'll try to implement that tomorrow.

> except that iam fine with the patch

Good, I'll resend once more when I've implemented the lowres option.

// Martin