70 lines
2.0 KiB
Dart
70 lines
2.0 KiB
Dart
/// NALU相关工具类与结构体
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import 'dart:typed_data';
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/// NALU单元结构体
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class NaluUnit {
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final int type; // NALU类型
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final List<int> data;
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NaluUnit(this.type, this.data);
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}
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class NaluUtils {
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/// 分离一帧数据中的所有NALU单元
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static List<NaluUnit> splitNalus(List<int> data) {
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final List<NaluUnit> nalus = [];
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int i = 0;
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List<int> startCodes = [];
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// 先找到所有起始码位置
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while (i < data.length - 3) {
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if (i < data.length - 4 &&
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data[i] == 0 && data[i + 1] == 0 && data[i + 2] == 0 && data[i + 3] == 1) {
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startCodes.add(i);
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i += 4;
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} else if (data[i] == 0 && data[i + 1] == 0 && data[i + 2] == 1) {
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startCodes.add(i);
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i += 3;
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} else {
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i++;
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}
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}
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// 补上结尾
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startCodes.add(data.length);
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// 分割NALU
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int nalusTotalLen = 0;
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for (int idx = 0; idx < startCodes.length - 1; idx++) {
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int start = startCodes[idx];
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int next = startCodes[idx + 1];
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int skip = (data[start] == 0 && data[start + 1] == 0 && data[start + 2] == 0 && data[start + 3] == 1) ? 4 : 3;
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int naluStart = start + skip;
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if (naluStart < next) {
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final nalu = data.sublist(start, next);
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nalusTotalLen += nalu.length;
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if (nalu.isNotEmpty) {
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nalus.add(NaluUnit(getNaluType(nalu), nalu));
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}
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}
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}
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if (nalus.isEmpty && data.isNotEmpty) {
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nalus.add(NaluUnit(getNaluType(data), data));
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} else if (nalusTotalLen < data.length) {
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nalus.add(NaluUnit(getNaluType(data.sublist(nalusTotalLen)), data.sublist(nalusTotalLen)));
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}
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return nalus;
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}
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/// 获取NALU类型
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static int getNaluType(List<int> nalu) {
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if (nalu.isEmpty) return -1;
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int offset = 0;
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if (nalu.length >= 4 && nalu[0] == 0x00 && nalu[1] == 0x00) {
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if (nalu[2] == 0x01)
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offset = 3;
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else if (nalu[2] == 0x00 && nalu[3] == 0x01)
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offset = 4;
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}
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if (nalu.length > offset) {
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return nalu[offset] & 0x1F;
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}
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return -1;
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}
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} |