I want to generate AAC in MP4 on-the-fly; can't, due to MOOV atom?, Was: rate conversion for aac in mp4 container Options

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In order to stream some PCM content, I would like to generate on-the-fly (without seek access to
the output file, one frame at the time) an aac payload in a mp4 container. I know I can do that with the
aac payload, but my problem is the mp4 container. Ffmpeg won't allow me to use stdin/stdout to
generate the mp4.

My understanding is that, the moov atom is the problem since it won't be available unless I've encoded
the whole file.

1) Is this an intrinsic limitation of the mp4 container?
2) Is there any way to "fake" the info in the moov atom?

Thanks!