Encoder settings to play back in reverse?

[boilerlt1]

I'm maintaining a program for a customer of ours that operates a bit like an industrial TiVo--it records a video signal from a scientific instrument at 1024x768 and allows the user to review the video stream.

We're encoding the video stream in DivX which sits in a Matroska container. Unfortunately we're stuck with this combo--we have a bunch of code that ties metadata about the readings from the scientific tool against the video, and we can't easily change video formats without breaking a ton of stuff.

We would like to figure out how to play DivX video backwards. I have a few questions:


Is it even possible to play a DivX-encoded video in reverse? If it matters, I'm performing encoding and playback using a DirectShow filter graph.
If the answer to #1 is "yes", are there certain settings that are required to make it work?


I'm currently trying the following encoder settings without any luck. The video looks OK, but my DirectShow graph control object tells me that I can't play my stream backwards.

-bv1 1536000 -vbv 20000000,16777216,16777216 -dir "C:\Temp\DivX" -b 2 -key 16 -profile=5 -windowed_fullsearch=3 -thread_delay=1

Can anyone suggest encoder settings that might work? Please keep in mind, we cannot stop and re-encode the video. It has to be encoded in a single pass so we can play through it almost immediately afterwards.

Thanks guys!

[Dark Shikari]

It is completely impossible to play an interframe-coded video in reverse in the traditional sense.

However, you can decode a full GOP forwards, cache the results in memory, then play it back (and while playing it back, decode the previous GOP forwards, and so forth).

[Guest]

If Avisynth is in your chain you can achieve what Dark says with the reverse() filter, assuming your decoder is frame accurate.