I am appending 2 mp4 files together using the following routine:

ffmpeg -y -i one.mp4 -vcodec copy -vbsf h264_mp4toannexb -acodec copy one.ts
ffmpeg -y -i two.mp4 -vcodec copy -vbsf h264_mp4toannexb -acodec copy two.ts

cat one.ts two.ts >> joined.ts

ffmpeg -y -i joined.ts -vcodec copy -acodec copy -absf aac_adtstoasc joined.mp4

This works fine, however when one.mp4 has no audio stream (the file is created using ffmpeg from a single jpeg, so no sound), the routine appends the files but the audio of two.mp4 starts at the beginning of the video. how should I solve this problem? Should I add switches to my append routine so that the audio in two.mp4 starts playing where it should, or should I add something to the ffmpeg command which creates the video from jpg?

here is the command I use to create one.mp4 which contains no sound:

ffmpeg -y -loop 1 -i blah.jpg -t 3 -vcodec libx264 one.mp4