I actually am doing this now with my sister in softball. She is a pitcher. I use my miniDVD to check her form in pitching and batting.
This comes down to your portable DVD player. Does it have A/V ports that can be connected from the camcorder to the DVD player? If so, any camcorder that has A/V outputs will work. If the DVD player does not have A/V ports, you will have to make sure that it can read from miniDVDs. If it has neither you're sort of out of luck unless you get another DVD player. Now to the camcorder issue if you have one of those requirements. At first, try to get a miniDVD camcorder. If your DVD player has the option to hook it up by A/V cables, that would work good. I would recommend Sony camcorders.
Then you would record on the miniDVD and then hook up the cables. Go to the playback mode then press "play" and when you get to the part that you want in slow motion, press "play" again and it will freeze then press the forward button to the right of "play". It will then begin to play slowly. When you want to stop, press "play". There ya go. Hope this helps.
I want to purchase a camcorder to film youth baseball pitchers and hitters and playback in very slow motion ...frame by frame advance. I want to do the playback on the ballfield so the players can see their form and mechanics. I want to playback using a portable DVD player as the playback screen. What camcorders can be used to do this frame by frame playback? Thanks.