ffmpeg merge 3 videos to a single widescreen video I have three .mp4  files and I want to generate a single widescreen video
For generating the widescreen I've worked out I can use this command assuming I've prepared the individual mp4 files:

ffmpeg -i teacher.mp4 -i student1.mp4 -i student2.mp4 -filter_complex "[0:v:0][1:v:0][2:v:0]hstack=inputs=3" -c:v libx264 -tune film -crf 16 -b:a 256k triple.mp4


Main Question:

1.triple.mp4 only has one audio,But I do need three audio tracks

2.three video playtogether in triple.mp4,can I controll the start time that   I set before?
For 1. use amix filter.
For 2. You could use trim filter to trim some of inputs. To delay one of videos, with black? frame, you could concat it with color source filter. But that needs quite convoluted filtergraph.