Okay, the example `avi-to-ppm` was only expecting a single stream in the input file, as it attempts to decode every single packet with the same decoder: https://github.com/zmwangx/rust-ffmpeg/blob/5d74df996d3927c03791cfa888b45b0dab3e07a2/examples/avi-to-ppm.rs#L32-L34.
As such
```console
$ ffmpeg -i example.avi -c:v copy -an example-video-only.avi
$ cargo run --example avi-to-ppm example-video-only.avi
```
should work just fine.
I've made it more tolerant in 3e9c83ec4e915139d0d0435463f007e7b7667cdb, which should work with your sample files just fine. Let me know if there are additional problems.