soundloader_opus.cpp

/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD 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 General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <https://www.gnu.org/licenses/old-licenses/gpl-2.0>.
 */
 
#include "stdafx.h"
 
#include "debug.h"
#include "misc/autorelease.hpp"
#include "random_access_file_type.h"
#include "sound_type.h"
#include "soundloader_type.h"
 
#include <opusfile.h>
 
#include "safeguards.h"
 
class SoundLoader_Opus : public SoundLoader {
public:
  SoundLoader_Opus() : SoundLoader("opus", "Opus sound loader", 10) {}
 
  static constexpr uint16_t OPUS_SAMPLE_RATE = 48000; 
  static constexpr uint8_t OPUS_SAMPLE_BITS = 16; 
 
  /* For good results, you will need at least 57 bytes (for a pure Opus-only stream). */
  static constexpr size_t MIN_OPUS_FILE_SIZE = 57U;
 
  /* It is recommended that this be large enough for at least 120 ms of data at 48 kHz per channel (5760 values per channel).
   * Smaller buffers will simply return less data, possibly consuming more memory to buffer the data internally. */
  static constexpr size_t DECODE_BUFFER_SAMPLES = 5760 * 2;
  static constexpr size_t DECODE_BUFFER_BYTES = DECODE_BUFFER_SAMPLES * sizeof(opus_int16);
 
  bool Load(SoundEntry &sound, bool new_format, std::vector<std::byte> &data) const override
  {
    if (!new_format) return false;
 
    /* At least 57 bytes are needed for an Opus-only file. */
    if (sound.file_size < MIN_OPUS_FILE_SIZE) return false;
 
    /* Test if data is an Ogg Opus stream, as identified by the initial file header. */
    auto filepos = sound.file->GetPos();
    std::vector<uint8_t> tmp(MIN_OPUS_FILE_SIZE);
    sound.file->ReadBlock(tmp.data(), tmp.size());
    if (op_test(nullptr, tmp.data(), tmp.size()) != 0) return false;
 
    /* Read the whole file into memory. */
    tmp.resize(sound.file_size);
    sound.file->SeekTo(filepos, SEEK_SET);
    sound.file->ReadBlock(tmp.data(), tmp.size());
 
    int error = 0;
    auto of = AutoRelease<OggOpusFile, op_free>(op_open_memory(tmp.data(), tmp.size(), &error));
    if (error != 0) {
      Debug(grf, 0, "SoundLoader_Opus: Unable to open stream.");
      return false;
    }
 
    size_t datapos = 0;
    for (;;) {
      data.resize(datapos + DECODE_BUFFER_BYTES);
 
      int link_index;
      int read = op_read(of.get(), reinterpret_cast<opus_int16 *>(&data[datapos]), DECODE_BUFFER_BYTES, &link_index);
      if (read == 0) break;
 
      if (read < 0) {
        Debug(grf, 0, "SoundLoader_Opus: Unexpected end of stream.");
        data.clear();
        return false;
      }
 
      int channels = op_channel_count(of.get(), link_index);
      if (channels != 1) {
        Debug(grf, 0, "SoundLoader_Opus: Unsupported channels {}, expected 1.", channels);
        data.clear();
        return false;
      }
 
      datapos += read * sizeof(opus_int16);
    }
 
    /* OpusFile always decodes at 48kHz. */
    sound.channels = 1;
    sound.bits_per_sample = OPUS_SAMPLE_BITS;
    sound.rate = OPUS_SAMPLE_RATE;
 
    /* We resized by DECODE_BUFFER_BYTES just before finally reading zero bytes, undo this. */
    data.resize(data.size() - DECODE_BUFFER_BYTES);
 
    return true;
  }
 
private:
  static SoundLoader_Opus instance;
};
 
/* static */ SoundLoader_Opus SoundLoader_Opus::instance{};