Jon’s Project Blog

The SCPD downloading script posted several years back seems to use some interesting mencoder encoder and so there always appears to be extra information packaged in the video file. Unfortunately, I needed to reduce the size of the streams and it appears that by using ffmpeg and extract the audio and video, and then muxing it back together seems to reduce the overhead file size by about 100 Mb.

I’ve included a simple bash script which you can modify below which takes a list of past streams to re-process (for windows you will need do figure out the dos equivalent). There doesn’t seem to be any loss in video quality and sound quality seems fine, so it seems like a free win.

Note: I have tried using x264 with high10 encoding, but it seems I cannot get the x264 10-bit compilation to produce proper ts video. The windows x264 10-bit from x264.nl seems to do a perfectly fine job, and ffmpeg in linux can then mux it with the audio, but using the linux compiled 10-bit, there seems to be problems with muxing it in ffmpeg, although the actual video only encode works as it should. If both can be used in conjuction, perhaps one could even attain a smaller file size by using 10-bit compression and the reduction in overhead explained here.

while [ -n "$1" ]
do
    echo "$1"
    ffmpeg -threads 0 -i $1 -vn -acodec copy $1.wma
    ffmpeg -threads 0 -i $1 -an -vcodec copy $1.wmv
    ffmpeg -threads 0 -async 1 -i $1.wma -i $1.wmv -vcodec copy $1.mkv
    rm -rf $1.wma $1.wmv
    shift
done

For those of you that interested in 10-bit encoding with the profile high10 in x264 here are some snippets:

# x264 --threads 0 --profile high10 -o $1.264 $1                                
# ffmpeg -threads 0 -i $1 -vn -acodec copy $1.wma                               
# ffmpeg -async 1 -threads 0 -i $1.264 -i $1.wma  -vcodec copy $1.final.mp4