Metadata Issues With MKV to MP4 using FFMpeg

[Makaveli84]

Hello,
I use MKVToolNix for simple mkv container manipulations, muxing, demuxing, etc.. In MKVToolNix, when muxing, i usually set a language and a title for the video and audio tracks.

Now i'm trying to batch convert a bunch of mkv files to mp4 container without reencoding. The mkvs mostly consist of h264 video and aac audio, though i don't think that changes anything in what i'm trying to do. To do that, i'm using ffmpeg with the following command lines:

ffmpeg -i in.mkv -acodec copy -vcodec copy out.mp4 (for videos having 1 single video stream + 1 single audio stream)

and

ffmpeg -i in.mkv -map 0:0 -vcodec copy -map 0:1 -acodec copy -map 0:2 -acodec copy out.mp4 (for videos having 1 single video stream + 2 audio streams)

However, only the language "tags" or metadata are being transferred. For example, in MediaInfo, the mkvs have a "title: bla bla" entry, whilst the mp4s don't. I've been reading about -metadata, -map_metadata and metadata_specifier for stream tagging in ffmpeg, but can't seem to figure out how to achieve what i want.

So my 2 questions are:

1) How can i automatically transfer the "title" data from mkvs to mp4s (it probably has to do with -map_metadata in ffmpeg)?

2) At least, how can i set "title" metadata for individual streams using ffmpeg (regardless of the values present in the mkv files, meaning how to set new values, regardless of the batch conversion i'm trying to do)??