merge m3u8 segments into mp4 not working

**Describe the bug**
i am trying to merge the segments from a m3u8 file and save/download it into mp4
but i keep getting an error

**Expected behavior**
Merge .ts files and save/download

**Desktop (please complete the following information):**
- OS: Linux
- Browser: brave/chromium
- Version: 91.0.4472.114

anything i am doing wrong?

Code
```
{
args: ['-i', 'index.m3u8', '-c', 'copy', 'video.mp4'],
inFilename: 'index.m3u8',
outFilename: 'video.mp4',
mediaType: 'video/mp4',
}
```

response
```
[fferr] [hls @ 0x1a33300] Failed to open segment 57 of playlist 0
log.js:15 [fferr] [hls @ 0x1a33300] Opening 'index58.ts' for reading
log.js:15 [fferr] [hls @ 0x1a33300] Failed to open segment 58 of playlist 0
log.js:15 [fferr] [hls @ 0x1a33300] Opening 'index59.ts' for reading
log.js:15 [fferr] [hls @ 0x1a33300] Failed to open segment 59 of playlist 0
log.js:15 [fferr] [hls @ 0x1a33300] Opening 'index60.ts' for reading
log.js:15 [fferr] [hls @ 0x1a33300] Failed to open segment 60 of playlist 0
log.js:15 [fferr] [hls @ 0x1a33300] Opening 'index61.ts' for reading
```