[Libav-user] Getting a Frame question

[M N]

08.09.2016, 19:23, "Carl Eugen Hoyos" <ceffmpeg at gmail.com>:
>  This sounds very unlikely / is not true.
>
>  This is still the same error (you cannot use codec_tag avc1 in mp4).
>  What is unclear about it?
>
>  Carl Eugen


And where did I use "codec_tag" in my code?! Does avformat_write_header() use codec_tag internally? Can you please give me a clear answer for my