[ffmpeg] Join ts files into a single ts/mp4 correctly (Audio stutter issue)

[Tsubasa]

So I've downloaded a livestream in realtime using N_m3u8DL-RE.
After the stream ended, N_m3u8DL-RE did not merge the downloaded ts files into one single file. So now I only got a whole list of ts files and I want to merge them into a single ts/mp4.

I tried the following command using ffmpeg:

Create filelist txt file:
(for %i in (*.ts) do @echo file '%i') > mylist.txt

Concat all ts files into output.ts:
ffmpeg -f concat -i mylist.txt -c copy output.ts

And when I executed the concat command, ffmpeg gives the following error many times:

start time for stream 0 is not set in estimate_timings_from_pts

The resulting output.ts file successfully merged all the TS segments, but the audio stutters approximately every 20 seconds and appears to have some sync issues.

How should I merge the TS files in this case? I've looked at the documentation for N_m3u8DL-RE, but there doesn't seem to be an option to merge files that have already been downloaded.

Below are the video info for the first two TS segments for reference:

General
ID                          : 1 (0x1)
Format                      : MPEG-TS
File size                   : 6.96 GiB
Duration                    : 2 h 52 min
Overall bit rate mode       : Variable
Overall bit rate            : 5 760 kb/s
Frame rate                  : 25.000 FPS

Video
ID                          : 256 (0x100)
Menu ID                     : 1 (0x1)
Format                      : AVC
Format/Info                 : Advanced Video Codec
Format profile              : Main@L5
Format settings             : CABAC / 4 Ref Frames
Format settings, CABAC      : Yes
Format settings, Reference  : 4 frames
Format settings, GOP        : M=1, N=15
Codec ID                    : 27
Duration                    : 2 h 52 min
Bit rate mode               : Variable
Maximum bit rate            : 5 500 kb/s
Width                       : 1 920 pixels
Height                      : 1 080 pixels
Display aspect ratio        : 16:9
Frame rate                  : 25.000 FPS
Standard                    : PAL
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 8 bits
Scan type                   : Progressive
Time code of first frame    : 02:04:37:20
Color range                 : Limited
Color primaries             : BT.709
Transfer characteristics    : BT.709
Matrix coefficients         : BT.709

Audio
ID                          : 257 (0x101)
Menu ID                     : 1 (0x1)
Format                      : AAC LC
Format/Info                 : Advanced Audio Codec Low Complexity
Format version              : Version 4
Muxing mode                 : ADTS
Codec ID                    : 15-2
Duration                    : 2 h 52 min
Bit rate mode               : Variable
Channel(s)                  : 2 channels
Channel layout              : L R
Sampling rate               : 48.0 kHz
Frame rate                  : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Delay relative to video     : -29 ms

General
ID                          : 1 (0x1)
Format                      : MPEG-TS
File size                   : 6.95 GiB
Duration                    : 2 h 52 min
Overall bit rate mode       : Variable
Overall bit rate            : 5 760 kb/s
Frame rate                  : 25.000 FPS

Video
ID                          : 256 (0x100)
Menu ID                     : 1 (0x1)
Format                      : AVC
Format/Info                 : Advanced Video Codec
Format profile              : Main@L5
Format settings             : CABAC / 4 Ref Frames
Format settings, CABAC      : Yes
Format settings, Reference  : 4 frames
Format settings, GOP        : M=1, N=15
Codec ID                    : 27
Duration                    : 2 h 52 min
Bit rate mode               : Variable
Maximum bit rate            : 5 500 kb/s
Width                       : 1 920 pixels
Height                      : 1 080 pixels
Display aspect ratio        : 16:9
Frame rate                  : 25.000 FPS
Standard                    : PAL
Color space                 : YUV
Chroma subsampling          : 4:2:0
Bit depth                   : 8 bits
Scan type                   : Progressive
Time code of first frame    : 02:04:41:10
Color range                 : Limited
Color primaries             : BT.709
Transfer characteristics    : BT.709
Matrix coefficients         : BT.709

Audio
ID                          : 257 (0x101)
Menu ID                     : 1 (0x1)
Format                      : AAC LC
Format/Info                 : Advanced Audio Codec Low Complexity
Format version              : Version 4
Muxing mode                 : ADTS
Codec ID                    : 15-2
Duration                    : 2 h 52 min
Bit rate mode               : Variable
Channel(s)                  : 2 channels
Channel layout              : L R
Sampling rate               : 48.0 kHz
Frame rate                  : 46.875 FPS (1024 SPF)
Compression mode            : Lossy
Delay relative to video     : 19 ms