ffmpeg
-i audio_and_video.ts
-i audio_only1.ts
-i audio_only2.ts
-i audio_only3.ts
-y
-filter_complex

//get audio from first input (and delay 1 millisecond)
[0:a]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo[mid0];
[mid0]adelay=1|1[nar];

//get second input (and delay 1 millisecond)
[1]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo[mid1];
[mid1]adelay=1|1[aud1];


//get third input (and delay it many milliseconds)
[2]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo[mid2];
[mid2]adelay=1745300|1745300[aud2];


//get fourth input (and delay it many milliseconds)
[3]aformat=sample_fmts=fltp:sample_rates=44100:channel_layouts=stereo[mid3];[mid3]adelay=1758700|1758700[aud3];

//put it all together:
[nar][aud1][aud2][aud3]amix=4[out]

//put the first input's video and then the filter (audio)
-map 0:v -map [out]

//rest shouldn't matter I don't think:
-strict experimental
-profile:v main
-level 3.1
-movflags +faststart
-c:a aac
-b:a 64K
-f mp4
output.mp4