I've downloaded a set of Youtube Videos that are part of the same episode. Currently I've tried converting them into mp4 using ffmpeg and then joining with MP4Box.
for f in *.flv; do ffmpeg -i "$f" -vcodec copy -acodec copy "${f%.flv}.mp4"; done
MP4Box -cat part0.mp4 -cat part1.mp4 -cat part2.mp4 -cat part3.mp4 -cat part4.mp4 -new video.mp4
However, upon joining with MP4Box opening the video in VLC does strange things. It seems create a video that has 3 different videos playing at the same time. Upon inspection, the videos have different bitrates and framerates, is this causing the problem?
Therefore, I'd like to re-encode the videos so that they are all the same and then joining them. Or is there a better way of accomplishing what I want?
Edit: I should have mentioned, I'd like to do this on the command line, as I want to semi-automate this process. Thanks!
Edit2: Seems like people are having similar problems as me with MP4Box. Sources:1 and 2. Then I tried avidemux, and it will merge them correctly but the audio is accelerated which is also cited here.
Final Edit and Solution: I followed the advice in this thread and converted the videos to mkv first, and then joined using mkvmerge, which worked great! Thanks!