| 1 | import 'dart:typed_data'; |
| 2 | |
| 3 | /// Merges multiple PCM WAV files (same format) into a single WAV. |
| 4 | Uint8List mergeWavFiles(List<Uint8List> wavFiles) { |
| 5 | if (wavFiles.isEmpty) return Uint8List(0); |
| 6 | if (wavFiles.length == 1) return wavFiles.first; |
| 7 | |
| 8 | final first = wavFiles.first; |
| 9 | final dataOffset = _findPcmDataOffset(first); |
| 10 | if (dataOffset == null) return first; |
| 11 | |
| 12 | final dataSizeOffset = _findDataChunkSizeOffset(first); |
| 13 | |
| 14 | final pcmBuilder = BytesBuilder(copy: false); |
| 15 | for (final wav in wavFiles) { |
| 16 | final offset = _findPcmDataOffset(wav); |
| 17 | if (offset != null && wav.length > offset) { |
| 18 | pcmBuilder.add(wav.sublist(offset)); |
| 19 | } |
| 20 | } |
| 21 | final pcmData = pcmBuilder.toBytes(); |
| 22 | |
| 23 | final header = Uint8List.fromList(first.sublist(0, dataOffset)); |
| 24 | _writeUint32LE(header, 4, header.length + pcmData.length - 8); |
| 25 | if (dataSizeOffset != null) { |
| 26 | _writeUint32LE(header, dataSizeOffset, pcmData.length); |
| 27 | } |
| 28 | |
| 29 | return Uint8List.fromList([...header, ...pcmData]); |
| 30 | } |
| 31 | |
| 32 | int? _findPcmDataOffset(Uint8List wav) { |
| 33 | final dataSizeOffset = _findDataChunkSizeOffset(wav); |
| 34 | return dataSizeOffset == null ? null : dataSizeOffset + 4; |
| 35 | } |
| 36 | |
| 37 | int? _findDataChunkSizeOffset(Uint8List wav) { |
| 38 | if (wav.length < 12) return null; |
| 39 | if (wav[0] != 0x52 || |
| 40 | wav[1] != 0x49 || |
| 41 | wav[2] != 0x46 || |
| 42 | wav[3] != 0x46 || |
| 43 | wav[8] != 0x57 || |
| 44 | wav[9] != 0x41 || |
| 45 | wav[10] != 0x56 || |
| 46 | wav[11] != 0x45) { |
| 47 | return null; |
| 48 | } |
| 49 | |
| 50 | var offset = 12; |
| 51 | while (offset + 8 <= wav.length) { |
| 52 | final chunkId = String.fromCharCodes(wav.sublist(offset, offset + 4)); |
| 53 | final chunkSize = _readUint32LE(wav, offset + 4); |
| 54 | if (chunkId == 'data') { |
| 55 | return offset + 4; |
| 56 | } |
| 57 | offset += 8 + chunkSize; |
| 58 | if (chunkSize.isOdd) offset++; |
| 59 | } |
| 60 | return null; |
| 61 | } |
| 62 | |
| 63 | int _readUint32LE(Uint8List bytes, int offset) { |
| 64 | return bytes[offset] | |
| 65 | (bytes[offset + 1] << 8) | |
| 66 | (bytes[offset + 2] << 16) | |
| 67 | (bytes[offset + 3] << 24); |
| 68 | } |
| 69 | |
| 70 | void _writeUint32LE(Uint8List bytes, int offset, int value) { |
| 71 | bytes[offset] = value & 0xff; |
| 72 | bytes[offset + 1] = (value >> 8) & 0xff; |
| 73 | bytes[offset + 2] = (value >> 16) & 0xff; |
| 74 | bytes[offset + 3] = (value >> 24) & 0xff; |
| 75 | } |