text: /*
   * Westwood SNDx codecs
   * Copyright (c) 2005 Konstantin Shishkov
   *
   * 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
   */
  
  #include "libavutil/intreadwrite.h"
  #include "avcodec.h"
  
  /**
   * @file
   * Westwood SNDx codecs.
   *
   * Reference documents about VQA format and its audio codecs
   * can be found here:
   * http://www.multimedia.cx
   */
  
  static const char ws_adpcm_2bit[] = { -2, -1, 0, 1};
  static const char ws_adpcm_4bit[] = {
      -9, -8, -6, -5, -4, -3, -2, -1,
       0,  1,  2,  3,  4,  5,  6,  8 };
  
  #define CLIP8(a) if(a>127)a=127;if(a<-128)a=-128;
  
  static av_cold int ws_snd_decode_init(AVCodecContext * avctx)
  {
  //    WSSNDContext *c = avctx->priv_data;
  
      avctx->sample_fmt = SAMPLE_FMT_S16;
      return 0;
  }
  
  static int ws_snd_decode_frame(AVCodecContext *avctx,
                  void *data, int *data_size,
                  AVPacket *avpkt)
  {
      const uint8_t *buf = avpkt->data;
      int buf_size = avpkt->size;
  //    WSSNDContext *c = avctx->priv_data;
  
      int in_size, out_size;
      int sample = 0;
      int i;
      short *samples = data;
  
      if (!buf_size)
          return 0;
  
      out_size = AV_RL16(&buf[0]);
      *data_size = out_size * 2;
      in_size = AV_RL16(&buf[2]);
      buf += 4;
  
      if (out_size > *data_size) {
          av_log(avctx, AV_LOG_ERROR, "Frame is too large to fit in buffer\n");
          return -1;
      }
      if (in_size > buf_size) {
          av_log(avctx, AV_LOG_ERROR, "Frame data is larger than input buffer\n");
          return -1;
      }
      if (in_size == out_size) {
          for (i = 0; i < out_size; i++)
              *samples++ = (*buf++ - 0x80) << 8;
          return buf_size;
      }
  
      while (out_size > 0) {
          int code;
          uint8_t count;
          code = (*buf) >> 6;
          count = (*buf) & 0x3F;
          buf++;
          switch(code) {
          case 0: /* ADPCM 2-bit */
              for (count++; count > 0; count--) {
                  code = *buf++;
                  sample += ws_adpcm_2bit[code & 0x3];
                  CLIP8(sample);
                  *samples++ = sample << 8;
                  sample += ws_adpcm_2bit[(code >> 2) & 0x3];
                  CLIP8(sample);
                  *samples++ = sample << 8;
                  sample += ws_adpcm_2bit[(code >> 4) & 0x3];
                  CLIP8(sample);
                  *samples++ = sample << 8;
                  sample += ws_adpcm_2bit[(code >> 6) & 0x3];
                  CLIP8(sample);
                  *samples++ = sample << 8;
                  out_size -= 4;
              }
              break;
          case 1: /* ADPCM 4-bit */
              for (count++; count > 0; count--) {
                  code = *buf++;
                  sample += ws_adpcm_4bit[code & 0xF];
                  CLIP8(sample);
                  *samples++ = sample << 8;
                  sample += ws_adpcm_4bit[code >> 4];
                  CLIP8(sample);
                  *samples++ = sample << 8;
                  out_size -= 2;
              }
              break;
          case 2: /* no compression */
              if (count & 0x20) { /* big delta */
                  char t;
                  t = count;
                  t <<= 3;
                  sample += t >> 3;
                  *samples++ = sample << 8;
                  out_size--;
              } else { /* copy */
                  for (count++; count > 0; count--) {
                      *samples++ = (*buf++ - 0x80) << 8;
                      out_size--;
                  }
                  sample = buf[-1] - 0x80;
              }
              break;
          default: /* run */
              for(count++; count > 0; count--) {
                  *samples++ = sample << 8;
                  out_size--;
              }
          }
      }
  
      return buf_size;
  }
  
  AVCodec ws_snd1_decoder = {
      "ws_snd1",
      AVMEDIA_TYPE_AUDIO,
      CODEC_ID_WESTWOOD_SND1,
      0,
      ws_snd_decode_init,
      NULL,
      NULL,
      ws_snd_decode_frame,
      .long_name = NULL_IF_CONFIG_SMALL("Westwood Audio (SND1)"),
  };
  