For h264 byte-stream format, we should set "streamheader".
"codec_data" is for avc.
We also set timestamp of the buffer to 0 because
mp4mux will be error if the PTS is none.
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https://gitlab.winehq.org/wine/wine/-/merge_requests/4600
This may be a matter of taste. I personally prefer to give variables a restricted scope, as I find this aids clarity, and -Wshadow can help prevent mistakes from this.
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https://gitlab.winehq.org/wine/vkd3d/-/merge_requests/506