text: /*
   * Copyright (c) CMU 1993 Computer Science, Speech Group
   *                        Chengxiang Lu and Alex Hauptmann
   * Copyright (c) 2005 Steve Underwood <steveu at coppice.org>
   * Copyright (c) 2009 Kenan Gillet
   * Copyright (c) 2010 Martin Storsjo
   *
   * This file is part of FFmpeg.
   *
   * FFmpeg is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * FFmpeg is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with FFmpeg; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  /**
   * @file
   * G.722 ADPCM audio decoder
   *
   * This G.722 decoder is a bit-exact implementation of the ITU G.722
   * specification for all three specified bitrates - 64000bps, 56000bps
   * and 48000bps. It passes the ITU tests.
   *
   * @note For the 56000bps and 48000bps bitrates, the lowest 1 or 2 bits
   *       respectively of each byte are ignored.
   */
  
  #include "libavutil/channel_layout.h"
  #include "libavutil/opt.h"
  #include "avcodec.h"
  #include "get_bits.h"
  #include "g722.h"
  #include "internal.h"
  
  #define OFFSET(x) offsetof(G722Context, x)
  #define AD AV_OPT_FLAG_AUDIO_PARAM | AV_OPT_FLAG_DECODING_PARAM
  static const AVOption options[] = {
  	{ "bits_per_codeword", "Bits per G722 codeword", OFFSET(bits_per_codeword), AV_OPT_TYPE_INT, { .i64 = 8 }, 6, 8, AD },
  	{ NULL }
  };
  
  static const AVClass g722_decoder_class = {
  	.class_name = "g722 decoder",
      .item_name  = av_default_item_name,
      .option     = options,
      .version    = LIBAVUTIL_VERSION_INT,
  };
  
  static av_cold int g722_decode_init(AVCodecContext * avctx)
  {
      G722Context *c = avctx->priv_data;
  
      avctx->channels       = 1;
      avctx->channel_layout = AV_CH_LAYOUT_MONO;
      avctx->sample_fmt     = AV_SAMPLE_FMT_S16;
  
      c->band[0].scale_factor = 8;
      c->band[1].scale_factor = 2;
      c->prev_samples_pos = 22;
  
      return 0;
  }
  
  static const int16_t low_inv_quant5[32] = {
       -35,   -35, -2919, -2195, -1765, -1458, -1219, -1023,
      -858,  -714,  -587,  -473,  -370,  -276,  -190,  -110,
      2919,  2195,  1765,  1458,  1219,  1023,   858,   714,
       587,   473,   370,   276,   190,   110,    35,   -35
  };
  
  static const int16_t * const low_inv_quants[3] = { ff_g722_low_inv_quant6,
                                                      low_inv_quant5,
                                              ff_g722_low_inv_quant4 };
  
  static int g722_decode_frame(AVCodecContext *avctx, void *data,
                               int *got_frame_ptr, AVPacket *avpkt)
  {
      G722Context *c = avctx->priv_data;
      AVFrame *frame = data;
      int16_t *out_buf;
      int j, ret;
      const int skip = 8 - c->bits_per_codeword;
      const int16_t *quantizer_table = low_inv_quants[skip];
      GetBitContext gb;
  
      /* get output buffer */
      frame->nb_samples = avpkt->size * 2;
      if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
          return ret;
      out_buf = (int16_t *)frame->data[0];
  
      init_get_bits(&gb, avpkt->data, avpkt->size * 8);
  
      for (j = 0; j < avpkt->size; j++) {
          int ilow, ihigh, rlow, rhigh, dhigh;
          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);
  
          ff_g722_update_low_predictor(&c->band[0], ilow >> (2 - skip));
  
          dhigh = c->band[1].scale_factor * ff_g722_high_inv_quant[ihigh] >> 10;
          rhigh = av_clip(dhigh + c->band[1].s_predictor, -16384, 16383);
  
          ff_g722_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;
          ff_g722_apply_qmf(c->prev_samples + c->prev_samples_pos - 24,
                            &xout1, &xout2);
          *out_buf++ = av_clip_int16(xout1 >> 11);
          *out_buf++ = av_clip_int16(xout2 >> 11);
          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;
          }
      }
  
      *got_frame_ptr = 1;
  
      return avpkt->size;
  }
  
  AVCodec ff_adpcm_g722_decoder = {
  	.name           = "g722",
      .long_name      = NULL_IF_CONFIG_SMALL("G.722 ADPCM"),
      .type           = AVMEDIA_TYPE_AUDIO,
      .id             = AV_CODEC_ID_ADPCM_G722,
      .priv_data_size = sizeof(G722Context),
      .init           = g722_decode_init,
      .decode         = g722_decode_frame,
      .capabilities   = CODEC_CAP_DR1,
      .priv_class     = &g722_decoder_class,
  };
  