If AVC and H264 are the "same" why do AVC MOVs turn white when re-encoding?

I work in post production audio and as part of our current workflow we ask to received Quicktime H264 .MOVs.

We then take these "small" video files and re-encode them as DV in order to playback flawlessly in Pro Tools.



Occasionally we receive MP4s...which never encode to DV successfully.



Even weirder is when we receive an AVC mov...which automatically turns white when re-encoding to DV.

I then have to go back to the editor and explain why I need this specific file.



So, in order to be more helpful to editors in these situations, is there anything I can suggest or ask for to be more specific and avoid this issues?



Thanks!

If AVC and H264 are the "same" why do AVC MOVs turn white when re-encoding?