Amiga CDXL converter

Posted by ALB42 on 14. Mai 2021No Comments

Someone asked me to try a CDXL converter (agaconv) but I did not get to work until i compiled it for myself on Linux. CDXL if you don’t know, was an very early movie format invented by Comodore to use for the Amiga CDTV, so it aimed at a 68000 with 7 MHz with a Single speed CD Rom (150 kb/s).

I tried to create some little movies with it and it works quite nicely, especially the agablaster is very good and fast for viewing on a native Amiga (if you have AGA I guess from the Name? I do not own an OCS or ECS Amiga so I can not try). To really get the movie to the small size (to meet the 150kb/s target) you really have to tweak the options. You need to lower den resolution to 160×100 (or lower) and the colors to 5bit (32 colors) or 6bit (HAM6) reduce the number of frames per second to 12 and recalculate the audio to mono 11025 kbit/s.

For me it was interesting to see how the movie would look like with such low quality, as example I took the OpenSource Big Bug Bunny Movie, which is nicely short and free to use without any legal problems.

For a faster Amiga (like a A1200) with a normal HD (around 1 MB/s) you can make the movie in something like 320×200 in 256 colors or even HAM8 and looks rather decent texts still readable sound is ok (just the 8 bit sound conversation is a bit weak, I increased the loudness a bit) and you get a nice movie result, just a bit big (around 500 MB for 8,5 minutes movie). Not all CDXL player can show this format (agablaster does it very nicely)

If you go to the original CDXL format description (as above), it becomes hard, it’s really tiny and greasy you can easily see the dithering and color reduction, texts (except Main Title) not readable at all, back in the days maybe nice (in 1991 or so, when CDTV came out) to at least see a movie but its much worse than CD-i (1990) or VCD (1993).

Because the agaconv is not directly running, need FFMPEG and java (if you want convert to HAM and it it needs a X Server) I created a docker container where all is installed inside working. I created two little scripts (one for Linux and one for Windows) to start the agaconv using the docker, all you need is installed docker and this script and of course the movie.

for example to create the standard movie format as decribed before you need to start it with (linux example):

agaconf.sh test.mkv test.cdxl --fps=12 --color-mode=ham6 --width=160 --audio-mode=mono --frequency=11025 --std-cdxl

Example movie: Big Bug Bunny with CDXL Standard settings ready for a stock Amiga.

I played this movie on my Amiga1200 and it looks like this:

I compiled 2 more versions, one with 32 colors (–color-mode=ocs5) and one for AGA Amigas (–color-mode=aga5) but the other settings stay the same.

So if you want to watch videos on your old Amiga try CDXL (and to convert you can use the docker container)

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