Code: static int er_supported(ERContext *s)
 {
     if(s->avctx->hwaccel && s->avctx->hwaccel->decode_slice           ||
        !s->cur_pic.f                                                  ||
       s->cur_pic.field_picture                                       ||
       s->avctx->profile == FF_PROFILE_MPEG4_SIMPLE_STUDIO
     )
         return 0;
     return 1;
}

Vulnerability Type: DoS 
CWE ID: CWE-617
Summary: In libavcodec in FFmpeg 4.0.1, improper maintenance of the consistency between the context profile field and studio_profile in libavcodec may trigger an assertion failure while converting a crafted AVI file to MPEG4, leading to a denial of service, related to error_resilience.c, h263dec.c, and mpeg4videodec.c.
Commit Message: avcodec/mpeg4videodec: Remove use of FF_PROFILE_MPEG4_SIMPLE_STUDIO as indicator of studio profile

The profile field is changed by code inside and outside the decoder,
its not a reliable indicator of the internal codec state.
Maintaining it consistency with studio_profile is messy.
Its easier to just avoid it and use only studio_profile

Fixes: assertion failure
Fixes: ffmpeg_crash_9.avi

Found-by: Thuan Pham, Marcel Böhme, Andrew Santosa and Alexandru Razvan Caciulescu with AFLSmart
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>