text: /*
   * RedSpark demuxer
   * Copyright (c) 2013 James Almer
   *
   * 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 "libavcodec/bytestream.h"
  #include "libavutil/intreadwrite.h"
  #include "avformat.h"
  #include "avio.h"
  #include "internal.h"
  
  #define HEADER_SIZE 4096
  
  typedef struct RedSparkContext {
      int         samples_count;
  } RedSparkContext;
  
  static int redspark_probe(AVProbeData *p)
  {
      uint32_t key, data;
      uint8_t header[8];
  
      /* Decrypt first 8 bytes of the header */
      data = AV_RB32(p->buf);
      data = data ^ (key = data ^ 0x52656453);
      AV_WB32(header, data);
      key = (key << 11) | (key >> 21);
  
      data = AV_RB32(p->buf + 4) ^ (((key << 3) | (key >> 29)) + key);
      AV_WB32(header + 4, data);
  
      if (AV_RB64(header) == AV_RB64("RedSpark"))
          return AVPROBE_SCORE_MAX;
  
      return 0;
  }
  
  static int redspark_read_header(AVFormatContext *s)
  {
      AVIOContext *pb = s->pb;
      RedSparkContext *redspark = s->priv_data;
      AVCodecContext *codec;
      GetByteContext gbc;
      int i, coef_off, ret = 0;
      uint32_t key, data;
      uint8_t *header, *pbc;
      AVStream *st;
  
      st = avformat_new_stream(s, NULL);
      if (!st)
          return AVERROR(ENOMEM);
      codec = st->codec;
  
      header = av_malloc(HEADER_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
      if (!header)
          return AVERROR(ENOMEM);
      pbc = header;
  
      /* Decrypt header */
      data = avio_rb32(pb);
      data = data ^ (key = data ^ 0x52656453);
      bytestream_put_be32(&pbc, data);
      key = (key << 11) | (key >> 21);
  
      for (i = 4; i < HEADER_SIZE; i += 4) {
          data = avio_rb32(pb) ^ (key = ((key << 3) | (key >> 29)) + key);
          bytestream_put_be32(&pbc, data);
      }
  
      codec->codec_id    = AV_CODEC_ID_ADPCM_THP;
      codec->codec_type  = AVMEDIA_TYPE_AUDIO;
  
      bytestream2_init(&gbc, header, HEADER_SIZE);
      bytestream2_seek(&gbc, 0x3c, SEEK_SET);
      codec->sample_rate = bytestream2_get_be32u(&gbc);
      if (codec->sample_rate <= 0 || codec->sample_rate > 96000) {
          av_log(s, AV_LOG_ERROR, "Invalid sample rate: %d\n", codec->sample_rate);
          ret = AVERROR_INVALIDDATA;
          goto fail;
      }
  
      st->duration = bytestream2_get_be32u(&gbc) * 14;
      redspark->samples_count = 0;
      bytestream2_skipu(&gbc, 10);
      codec->channels = bytestream2_get_byteu(&gbc);
      if (!codec->channels) {
          ret = AVERROR_INVALIDDATA;
          goto fail;
      }
  
      coef_off = 0x54 + codec->channels * 8;
      if (bytestream2_get_byteu(&gbc)) // Loop flag
          coef_off += 16;
  
      codec->extradata_size = 32 * codec->channels;
      codec->extradata = av_malloc(codec->extradata_size);
      if (!codec->extradata) {
          ret = AVERROR(ENOMEM);
          goto fail;
      }
  
      /* Get the ADPCM table */
      bytestream2_seek(&gbc, coef_off, SEEK_SET);
      for (i = 0; i < codec->channels; i++) {
          if (bytestream2_get_bufferu(&gbc, codec->extradata + i * 32, 32) != 32) {
              ret = AVERROR_INVALIDDATA;
              goto fail;
          }
          bytestream2_skipu(&gbc, 14);
      }
  
      avpriv_set_pts_info(st, 64, 1, codec->sample_rate);
  
  fail:
      av_free(header);
  
      return ret;
  }
  
  static int redspark_read_packet(AVFormatContext *s, AVPacket *pkt)
  {
      AVCodecContext *codec = s->streams[0]->codec;
      RedSparkContext *redspark = s->priv_data;
      uint32_t size = 8 * codec->channels;
      int ret;
  
      if (url_feof(s->pb) || redspark->samples_count == s->streams[0]->duration)
          return AVERROR_EOF;
  
      ret = av_get_packet(s->pb, pkt, size);
      if (ret != size) {
          av_free_packet(pkt);
          return AVERROR(EIO);
      }
  
      pkt->duration = 14;
      redspark->samples_count += pkt->duration;
      pkt->stream_index = 0;
  
      return ret;
  }
  
  AVInputFormat ff_redspark_demuxer = {
      .name           =   "redspark",
      .long_name      =   NULL_IF_CONFIG_SMALL("RedSpark"),
      .priv_data_size =   sizeof(RedSparkContext),
      .read_probe     =   redspark_probe,
      .read_header    =   redspark_read_header,
      .read_packet    =   redspark_read_packet,
      .extensions     =   "rsd",
  };
  