10,000,000 FPS x264 Output from HFYU input

[Isochroma]

Using both v. 260 and 270D (commandline versions), with these inputs:

AviSynth script:

AviSource("filename.avi")
ConvertToYV12()

The input filename.avi has these specs:

720x480
23.976 FPS
HFYU (huffYUV YUY2 mode)
7047 frames

Then, using any commandline for x264, the AVS script is specified along with an output .mp4 file. I've had perfect success using this method with AVS scripts using DGMPEGDEC in place of AviSource. Today I finally got around to trying AviSource, and the following bug cropped up: playback in MPC 6.4.8.4 is extremely rapid (instantaneous). Properties shows that the file has a framerate of 10,000,000 FPS.

Thinking that my video editing program (source of the above file) might be the problem, I ran the original 1.8 GB file through VirtualDub 1.5.10 in Fast Recompress mode with the same HFYU settings (YUY2, Predict Gradient) on recompression. The resulting file, while about 2MB smaller (indicating excess bits from Vegas 6.0), nonetheless produced the same output.

All AVI programs report no problems with this file. I haven't run it through VDub's index regeneration yet.

If the encoding is stopped at any point by CTRL-C, the resulting file is valid and plays at 23.976. If encoding is allowed to continue to completion, result is a file that plays at 10,000,000 FPS (media player classic, 6.4.8.4 in File => Properties).

Decode filter is Nero AVC decoder. Works fine on all other files.

Same process has been tested on two machines, with same results.
VFW version works fine in all tests.

[Isochroma]

After exhaustive testing, I have determined that if my source video is clipped at about 4000 frames, everything works ok. So, I'm testing different frame lengths and gradually closing in on the error. It is most likely a Vegas 6.0 issue.

It should be noted, however, that the VFW version of x264 doesn't have any problems with the video stream, and neither does any other VFW editor/compressor.