Thank you, Mark.  I will try the wave/envelope generator.  My media is all photo jpeg codec.  Are there advantages to using HAP or ProRes422 over photo jpeg?   

 It looks like Marks message was truncated. I am pretty sure he was going to say to use Codecs that compress each frame individually. ProRes or HAP are probably the most common.

Thanks Ryan, I edited my post to fill in the blanks.

You should only try this for movies that do not require

 It looks like Marks message was truncated. I am pretty sure he was going to say to use Codecs that compress each frame individually. ProRes or HAP are probably the most common.
For this type of custom control I would recommend Hap.
H264 would be an example of a codec that should not be used for this as each frame is dependant on the decompression of other frames. For this reason H264 is also a bad/terrible choice for reverse playback.

Ok, so the windows playback engine is not capable of playing reverse, I knew I read somewhere about the reverse limit.

Best Michel

Isadora has not supported the +10 to -10 speed since Isadora 1.x when Quicktime was the only playback engine for both Mac and Windows.

@Michel is basically correct about the limits of AVFoundation, except that it can actually play any speed between -2 and +2. When we needed to adopt AVFoundation in the macOS version, we adopted these limits for all Movie Players, whether QuicKTime or AVFoundation was being used. Windows movie playing engines do not allow reverse playback, but I created a hack to allow that to happen.

In any case, the limit is -2 to +2 in Isadora 2 and Isadora 3.

You can attempt to simulate higher speeds by setting the speed to 0 and sending a continuous value (e.g., from a Wave Generator or Envelope Generator) into the position input of the Movie Player. You should only try this for movies where the codec compresses each frame of video individually, e.g., HAP, Apple Pro Res 422. You don't want to do this with H264 or other codecs where partial frames are stored, as you'll get really bad performance.

Best Wishes,
Mark

This has to do with the playback engine AVfoundation that does not support more. the old Quicktime engine could do more, but apple dropped support for it and it's not working in Catalina anymore because its 32bit. I think that Isadora is capable of playing the movie backward is because @mark found a way to do so. AVfoundation supports 0.5 to 2, as far as I know.

Best Michel