// Windows
copy /b segment1_0_av.ts+segment2_0_av.ts+segment3_0_av.ts all.ts
ffmpeg -i all.ts -acodec copy -vcodec copy all.mp4

// GNU/Linux, using bash:
cat segment1_0_av.ts segment2_0_av.ts segment3_0_av.ts > all.ts
ffmpeg -i all.ts -acodec copy -vcodec copy all.mp4