264 lines
7.6 KiB
Go
264 lines
7.6 KiB
Go
package main
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import (
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"fmt"
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"os"
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"path/filepath"
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"strconv"
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"github.com/Eyevinn/mp4ff/mp4"
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)
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func main() {
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if len(os.Args) < 4 {
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fmt.Println("用法: split_merged <输入文件> <输出目录> <段数>")
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os.Exit(1)
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}
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inputPath := os.Args[1]
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outDir := os.Args[2]
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numSegments, err := strconv.Atoi(os.Args[3])
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if err != nil || numSegments <= 0 {
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fmt.Printf("无效的段数: %s\n", os.Args[3])
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os.Exit(1)
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}
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// 读取合并文件
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f, err := mp4.ReadMP4File(inputPath)
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if err != nil {
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fmt.Printf("读取文件失败: %v\n", err)
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os.Exit(1)
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}
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if err := os.MkdirAll(outDir, 0755); err != nil {
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fmt.Printf("创建输出目录失败: %v\n", err)
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os.Exit(1)
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}
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// 收集每轨道按段划分的 sample 范围
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type trakInfo struct {
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trak *mp4.TrakBox
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samples uint32 // 总 sample 数
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perSeg uint32 // 每段 sample 数
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}
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var traks []trakInfo
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for _, trak := range f.Moov.Traks {
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stbl := trak.Mdia.Minf.Stbl
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if stbl.Stsz != nil {
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totalSamples := stbl.Stsz.SampleNumber
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perSeg := totalSamples / uint32(numSegments)
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traks = append(traks, trakInfo{
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trak: trak,
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samples: totalSamples,
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perSeg: perSeg,
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})
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fmt.Printf("轨道 %s: 总 %d samples, 每段 %d\n", trak.Mdia.Hdlr.HandlerType, totalSamples, perSeg)
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}
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}
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if len(traks) == 0 {
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fmt.Println("未找到可分割的轨道")
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os.Exit(1)
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}
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// 逐段切分
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for seg := 0; seg < numSegments; seg++ {
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outPath := filepath.Join(outDir, fmt.Sprintf("seg_%d.mp4", seg))
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fmt.Printf("切分第 %d 段 -> %s\n", seg, outPath)
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outFile := mp4.NewFile()
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outFile.Ftyp = f.Ftyp
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outFile.Moov = f.Moov // 稍后会修改
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// 为每轨道创建仅包含本段 samples 的 stbl
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for _, ti := range traks {
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stbl := ti.trak.Mdia.Minf.Stbl
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startSample := seg * int(ti.perSeg)
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endSample := startSample + int(ti.perSeg)
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if seg == numSegments-1 {
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endSample = int(ti.samples) // 最后一段拿剩余所有 samples
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}
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fmt.Printf(" 轨道 %s: samples [%d, %d)\n", ti.trak.Mdia.Hdlr.HandlerType, startSample, endSample)
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// 拷贝 stsz entry（只保留本段范围）
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if stbl.Stsz != nil {
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newStsz := &mp4.StszBox{}
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if stbl.Stsz.SampleUniformSize > 0 {
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newStsz.SampleUniformSize = stbl.Stsz.SampleUniformSize
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newStsz.SampleNumber = uint32(endSample - startSample)
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} else {
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newStsz.SampleSize = make([]uint32, endSample-startSample)
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copy(newStsz.SampleSize, stbl.Stsz.SampleSize[startSample:endSample])
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newStsz.SampleNumber = uint32(len(newStsz.SampleSize))
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}
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stbl.Stsz = newStsz
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}
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// 计算本段 chunk 范围：通过 stsc 找到对应的 chunk
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// 直接根据 perSeg chunks 计算。每段 chunks = totalChunks / numSegments
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chunkCount := uint32(0)
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if stbl.Stco != nil {
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chunkCount = uint32(len(stbl.Stco.ChunkOffset))
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} else if stbl.Co64 != nil {
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chunkCount = uint32(len(stbl.Co64.ChunkOffset))
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}
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perSegChunks := chunkCount / uint32(numSegments)
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startChunk := seg * int(perSegChunks)
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endChunk := startChunk + int(perSegChunks)
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if seg == numSegments-1 {
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endChunk = int(chunkCount)
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}
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// 重新构建 stco（只保留本段 chunk）
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if stbl.Stco != nil {
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oldChunks := stbl.Stco.ChunkOffset
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stbl.Stco.ChunkOffset = oldChunks[startChunk:endChunk]
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// 调整偏移量：减去 mdat 中本段数据的起始位置
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baseOffset := oldChunks[startChunk]
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for i := range stbl.Stco.ChunkOffset {
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stbl.Stco.ChunkOffset[i] -= baseOffset
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}
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}
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if stbl.Co64 != nil {
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oldChunks := stbl.Co64.ChunkOffset
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stbl.Co64.ChunkOffset = oldChunks[startChunk:endChunk]
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baseOffset := oldChunks[startChunk]
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for i := range stbl.Co64.ChunkOffset {
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stbl.Co64.ChunkOffset[i] -= baseOffset
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}
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}
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// 重新构建 stsc（只保留本段 chunk 的 entries）
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if stbl.Stsc != nil {
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var newEntries []mp4.StscEntry
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for _, e := range stbl.Stsc.Entries {
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if e.FirstChunk-1 >= uint32(startChunk) && e.FirstChunk-1 < uint32(endChunk) {
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newEntries = append(newEntries, mp4.StscEntry{
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FirstChunk: e.FirstChunk - uint32(startChunk),
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SamplesPerChunk: e.SamplesPerChunk,
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SampleDescriptionIndex: e.SampleDescriptionIndex,
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})
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}
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}
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stbl.Stsc.Entries = newEntries
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}
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// 重设 stts（重建，只保留本段 samples 对应的时间）
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if stbl.Stts != nil {
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newStts := &mp4.SttsBox{}
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currentSample := uint32(0)
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for i := range stbl.Stts.SampleCount {
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count := stbl.Stts.SampleCount[i]
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delta := stbl.Stts.SampleTimeDelta[i]
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nextSample := currentSample + count
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if nextSample <= uint32(startSample) {
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currentSample = nextSample
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continue
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}
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if currentSample >= uint32(endSample) {
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break
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}
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overlapStart := uint32(0)
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if currentSample < uint32(startSample) {
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overlapStart = uint32(startSample) - currentSample
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}
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overlapEnd := count
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if nextSample > uint32(endSample) {
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overlapEnd = uint32(endSample) - currentSample
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}
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if overlapStart < overlapEnd {
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newStts.SampleCount = append(newStts.SampleCount, overlapEnd-overlapStart)
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newStts.SampleTimeDelta = append(newStts.SampleTimeDelta, delta)
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}
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currentSample = nextSample
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}
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stbl.Stts = newStts
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}
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// 修正 stco 偏移：加上 ftyp+moov+mdat_header 偏移
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mdatDataStart := uint32(0) // 稍后在写入时修正
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_ = mdatDataStart
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}
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// 提取本段 mdat 数据
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mdatStart := uint32(0)
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if len(traks) > 0 && traks[0].trak.Mdia.Minf.Stbl.Stco != nil {
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// 使用第一个轨道的第一个 chunk 偏移量作为数据起始位置
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mdatStart = traks[0].trak.Mdia.Minf.Stbl.Stco.ChunkOffset[0]
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}
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// 重构 mdat：从合并文件提取本段数据
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outFile.Mdat = &mp4.MdatBox{}
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mdatPayloadLen := uint64(0)
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// 计算本段 mdat 数据长度
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for _, ti := range traks {
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stbl := ti.trak.Mdia.Minf.Stbl
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if stbl.Stsz != nil {
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if stbl.Stsz.SampleUniformSize > 0 {
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mdatPayloadLen += uint64(stbl.Stsz.SampleUniformSize) * uint64(stbl.Stsz.SampleNumber)
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} else {
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for _, s := range stbl.Stsz.SampleSize {
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mdatPayloadLen += uint64(s)
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}
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}
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}
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}
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if mdatPayloadLen > 0 {
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segData := make([]byte, mdatPayloadLen)
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// 从原始 mdat 拷贝
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offset := uint64(mdatStart)
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_ = offset
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copyPos := uint64(0)
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for _, ti := range traks {
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stbl := ti.trak.Mdia.Minf.Stbl
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if stbl.Stsz != nil {
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if stbl.Stsz.SampleUniformSize > 0 {
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dataLen := uint64(stbl.Stsz.SampleUniformSize) * uint64(stbl.Stsz.SampleNumber)
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copy(segData[copyPos:], f.Mdat.Data[offset:offset+dataLen])
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copyPos += dataLen
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offset += dataLen
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} else {
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for _, s := range stbl.Stsz.SampleSize {
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copy(segData[copyPos:], f.Mdat.Data[offset:offset+uint64(s)])
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copyPos += uint64(s)
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offset += uint64(s)
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}
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}
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}
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}
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outFile.Mdat.SetData(segData)
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}
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// 更新 mdhd/tkhd/mvhd 时长
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outFile.Moov.Mvhd = f.Moov.Mvhd // 拷贝原始 mvhd
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// 简化处理：直接使用原始 mvhd 时长
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// 重建 Children
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outFile.Children = []mp4.Box{outFile.Ftyp, outFile.Moov, outFile.Mdat}
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// 修正 stco 偏移：调整到实际文件位置
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combinedBase := outFile.Ftyp.Size() + outFile.Moov.Size() + outFile.Mdat.HeaderSize()
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for _, ti := range traks {
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stbl := ti.trak.Mdia.Minf.Stbl
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if stbl.Stco != nil {
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for i := range stbl.Stco.ChunkOffset {
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stbl.Stco.ChunkOffset[i] += uint32(combinedBase)
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}
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}
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}
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if err := mp4.WriteToFile(outFile, outPath); err != nil {
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fmt.Printf("写入 %s 失败: %v\n", outPath, err)
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continue
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}
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fmt.Printf(" 完成: %s\n", outPath)
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}
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fmt.Println("切分完成")
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}
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