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/***
This file is part of snapcast
Copyright (C) 2014-2025 Johannes Pohl
This program 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, either version 3 of the License, or
(at your option) any later version.
This program 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 this program. If not, see <http://www.gnu.org/licenses/>.
***/
// prototype/interface header file
#include "pcm_decoder.hpp"
// local headers
#include "common/endian.hpp"
#include "common/snap_exception.hpp"
namespace decoder
{
static constexpr auto ID_RIFF = 0x46464952;
static constexpr auto ID_WAVE = 0x45564157;
static constexpr auto ID_FMT = 0x20746d66;
static constexpr auto ID_DATA = 0x61746164;
/// RIFF wave header
/// See https://en.wikipedia.org/wiki/WAV
struct riff_wave_header
{
uint32_t riff_id; ///< "RIFF"
uint32_t riff_sz; ///< file size - 8
uint32_t wave_id; ///< "WAVE"
};
/// Chunk header
/// See https://en.wikipedia.org/wiki/WAV
struct chunk_header
{
uint32_t id; ///< id
uint32_t sz; ///< size
};
/// Chunk format
/// See https://en.wikipedia.org/wiki/WAV
struct chunk_fmt
{
uint16_t audio_format; ///< format
uint16_t num_channels; ///< channels
uint32_t sample_rate; ///< sample rate
uint32_t byte_rate; ///< byte rate
uint16_t block_align; ///< block align
uint16_t bits_per_sample; ///< bps
};
PcmDecoder::PcmDecoder() : Decoder()
{
}
bool PcmDecoder::decode(msg::PcmChunk* /*chunk*/)
{
return true;
}
SampleFormat PcmDecoder::setHeader(msg::CodecHeader* chunk)
{
if (chunk->payloadSize < 44)
throw SnapException("PCM header too small");
struct riff_wave_header riff_wave_header;
struct chunk_header chunk_header;
struct chunk_fmt chunk_fmt;
chunk_fmt.sample_rate = SWAP_32(0);
chunk_fmt.bits_per_sample = SWAP_16(0);
chunk_fmt.num_channels = SWAP_16(0);
size_t pos(0);
memcpy(&riff_wave_header, chunk->payload + pos, sizeof(riff_wave_header));
pos += sizeof(riff_wave_header);
if ((SWAP_32(riff_wave_header.riff_id) != ID_RIFF) || (SWAP_32(riff_wave_header.wave_id) != ID_WAVE))
throw SnapException("Not a riff/wave header");
bool moreChunks(true);
do
{
if (pos + sizeof(chunk_header) > chunk->payloadSize)
throw SnapException("riff/wave header incomplete");
memcpy(&chunk_header, chunk->payload + pos, sizeof(chunk_header));
pos += sizeof(chunk_header);
switch (SWAP_32(chunk_header.id))
{
case ID_FMT:
if (pos + sizeof(chunk_fmt) > chunk->payloadSize)
throw SnapException("riff/wave header incomplete");
memcpy(&chunk_fmt, chunk->payload + pos, sizeof(chunk_fmt));
pos += sizeof(chunk_fmt);
/// If the format header is larger, skip the rest
if (SWAP_32(chunk_header.sz) > sizeof(chunk_fmt))
pos += (SWAP_32(chunk_header.sz) - sizeof(chunk_fmt));
break;
case ID_DATA:
/// Stop looking for chunks
moreChunks = false;
break;
default:
/// Unknown chunk, skip bytes
pos += SWAP_32(chunk_header.sz);
}
} while (moreChunks);
if (SWAP_32(chunk_fmt.sample_rate) == 0)
throw SnapException("Sample format not found");
SampleFormat sampleFormat(SWAP_32(chunk_fmt.sample_rate), SWAP_16(chunk_fmt.bits_per_sample), SWAP_16(chunk_fmt.num_channels));
return sampleFormat;
}
} // namespace decoder
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