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 <stdint.h>
  
  #include "libavutil/channel_layout.h"
  #include "libavutil/common.h"
  #include "libavutil/intreadwrite.h"
  #include "avcodec.h"
  #include "internal.h"
  
  /**
   * @file
   * Westwood SNDx codecs
   *
   * Reference documents about VQA format and its audio codecs
   * can be found here:
   * http://www.multimedia.cx
   */
  
  static const int8_t ws_adpcm_4bit[] = {
      -9, -8, -6, -5, -4, -3, -2, -1,
       0,  1,  2,  3,  4,  5,  6,  8
  };
  
  static av_cold int ws_snd_decode_init(AVCodecContext *avctx)
  {
      avctx->channels       = 1;
      avctx->channel_layout = AV_CH_LAYOUT_MONO;
      avctx->sample_fmt     = AV_SAMPLE_FMT_U8;
  
      return 0;
  }
  
  static int ws_snd_decode_frame(AVCodecContext *avctx, void *data,
                                 int *got_frame_ptr, AVPacket *avpkt)
  {
      AVFrame *frame     = data;
      const uint8_t *buf = avpkt->data;
      int buf_size       = avpkt->size;
  
      int in_size, out_size, ret;
      int sample = 128;
      uint8_t *samples;
      uint8_t *samples_end;
  
      if (!buf_size)
          return 0;
  
      if (buf_size < 4) {
          av_log(avctx, AV_LOG_ERROR, "packet is too small\n");
          return AVERROR(EINVAL);
      }
  
      out_size = AV_RL16(&buf[0]);
      in_size  = AV_RL16(&buf[2]);
      buf += 4;
  
      if (in_size > buf_size) {
          av_log(avctx, AV_LOG_ERROR, "Frame data is larger than input buffer\n");
          return AVERROR_INVALIDDATA;
      }
  
      /* get output buffer */
      frame->nb_samples = out_size;
      if ((ret = ff_get_buffer(avctx, frame, 0)) < 0)
          return ret;
      samples     = frame->data[0];
      samples_end = samples + out_size;
  
      if (in_size == out_size) {
          memcpy(samples, buf, out_size);
          *got_frame_ptr = 1;
          return buf_size;
      }
  
      while (samples < samples_end && buf - avpkt->data < buf_size) {
          int code, smp, size;
          uint8_t count;
          code  = *buf >> 6;
          count = *buf & 0x3F;
          buf++;
  
          /* make sure we don't write past the output buffer */
          switch (code) {
          case 0:  smp = 4 * (count + 1);                break;
          case 1:  smp = 2 * (count + 1);                break;
          case 2:  smp = (count & 0x20) ? 1 : count + 1; break;
          default: smp = count + 1;                      break;
          }
          if (samples_end - samples < smp)
              break;
  
          /* make sure we don't read past the input buffer */
          size = ((code == 2 && (count & 0x20)) || code == 3) ? 0 : count + 1;
          if ((buf - avpkt->data) + size > buf_size)
              break;
  
          switch (code) {
          case 0: /* ADPCM 2-bit */
              for (count++; count > 0; count--) {
                  code = *buf++;
                  sample += ( code       & 0x3) - 2;
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
                  sample += ((code >> 2) & 0x3) - 2;
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
                  sample += ((code >> 4) & 0x3) - 2;
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
                  sample +=  (code >> 6)        - 2;
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
              }
              break;
          case 1: /* ADPCM 4-bit */
              for (count++; count > 0; count--) {
                  code = *buf++;
                  sample += ws_adpcm_4bit[code & 0xF];
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
                  sample += ws_adpcm_4bit[code >> 4];
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
              }
              break;
          case 2: /* no compression */
              if (count & 0x20) { /* big delta */
                  int8_t t;
                  t = count;
                  t <<= 3;
                  sample += t >> 3;
                  sample = av_clip_uint8(sample);
                  *samples++ = sample;
              } else { /* copy */
                  memcpy(samples, buf, smp);
                  samples += smp;
                  buf     += smp;
                  sample = buf[-1];
              }
              break;
          default: /* run */
              memset(samples, sample, smp);
              samples += smp;
          }
      }
  
      frame->nb_samples = samples - frame->data[0];
      *got_frame_ptr    = 1;
  
      return buf_size;
  }
  
  AVCodec ff_ws_snd1_decoder = {
      .name           = "ws_snd1",
      .long_name      = NULL_IF_CONFIG_SMALL("Westwood Audio (SND1)"),
      .type           = AVMEDIA_TYPE_AUDIO,
      .id             = AV_CODEC_ID_WESTWOOD_SND1,
      .init           = ws_snd_decode_init,
      .decode         = ws_snd_decode_frame,
      .capabilities   = AV_CODEC_CAP_DR1,
  };
  