Muxing commands of Drive to Barley Lake video:

- The output from avidemux to speed up to 4*:
$ ffmpeg -i 2023_0311_Barley_Lake_0.mp4 -filter_complex '[0:v]setpts=0.25*PTS[v];[0:a]atempo=4[a]' -map '[v]' -map '[a]' 2023_0311_Barley_Lake_0s4.mp4
- This could've been done in the same step, but I did it separately, since I'm fairly new to ffmpeg cli: Copy the mono channel to the front left and front right, and upscale to 48khz:
$ ffmpeg -i 2023_0311_Barley_Lake_0s4.mp4 -ac 2 -ar 48000 2023_0311_Barley_Lake_0s4ar.mp4
- Mixing the soundtrack audio channel with the original environmental noise:
$ ffmpeg -i 2023_0311_Barley_Lake_0s4ar.mp4 -i apl00.webm -c:v copy -map 0:v:0 -filter_complex "[0:a][1:a]amerge=inputs=2,pan=stereo|c0<c0+c2|c1<c1+c3[a]" -map "[a]" 2023_0311_Barley_Lake_0_final.mp4

Muxing commands of Drive home from Barley Lake video:
- The output from avidemux to speed up to 4*:
$ ffmpeg -i 2023_0311_Barley_Lake_1.mp4 -filter_complex '[0:v]setpts=0.25*PTS[v];[0:a]atempo=4[a]' -map '[v]' -map '[a]' 2023_0311_Barley_Lake_1s4.mp4
- This could've been done in the same step, but I did it separately, since I'm fairly new to ffmpeg cli: Copy the mono channel to the front left and front right, and upscale to 48khz:
$ ffmpeg -i 2023_0311_Barley_Lake_1s4.mp4 -ac 2 -ar 48000 2023_0311_Barley_Lake_1s4ar.mp4
- Mixing the soundtrack audio channel with the original environmental noise:
$ ffmpeg -i 2023_0311_Barley_Lake_1s4ar.mp4 -i apl01.webm -c:v copy -map 0:v:0 -filter_complex "[0:a][1:a]amerge=inputs=2,pan=stereo|c0<c0+c2|c1<c1+c3[a]" -map "[a]" 2023_0311_Barley_Lake_1_final.mp4