func: static int libgsm_decode_frame(AVCodecContext *avctx,
  
                                 void *data, int *data_size,
  
                                 AVPacket *avpkt) {
  
      uint8_t *buf = avpkt->data;
  
      int buf_size = avpkt->size;
  
      int out_size = avctx->frame_size * av_get_bytes_per_sample(avctx->sample_fmt);
  
  
  
      if (*data_size < out_size) {
  
          av_log(avctx, AV_LOG_ERROR, "Output buffer is too small\n");
  
          return AVERROR(EINVAL);
  
      }
  
  
  
      if (buf_size < avctx->block_align) {
  
          av_log(avctx, AV_LOG_ERROR, "Packet is too small\n");
  
          return AVERROR_INVALIDDATA;
  
      }
  
  
  
      switch(avctx->codec_id) {
  
      case CODEC_ID_GSM:
  
          if(gsm_decode(avctx->priv_data,buf,data)) return -1;
  
          break;
  
      case CODEC_ID_GSM_MS:
  
          if(gsm_decode(avctx->priv_data,buf,data) ||
  
             gsm_decode(avctx->priv_data,buf+33,((int16_t*)data)+GSM_FRAME_SIZE)) return -1;
  
      }
  
  
  
      *data_size = out_size;
  
      return avctx->block_align;
  
  }
  