#9 Edit some mp4 atoms with mp4box

[Kurtnoise]

It could be great if we have the possibility to edit
the mdhd atom (for change/modify the language name) and
the hdlr atom where is stored the component name.

Thanks.

[Jean Le Feuvre]

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I don't think the handler name will ever be editable through
MP4Box - this is purely informative data that should be
ignored by file readers. I'll add the track language support one
of these days, it is indeed badly missing.

[bond]

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jean: just a question:

people start already heavily changing the handler name in
hexeditor like tools, like apple's dumpster

i wanted to ask whether this is ok to do? eg lets say the
name set by mp4box is 10 characters long, but people
change the name to a 5 or 15 characters long name. is this
ok to do or will this fuck up the file (eg as the atom size isnt
correct anymore or something like this)?

[Jean Le Feuvre]

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if they change with a shorter name there shouldn't be any
issue. Otherwise results are unpredictable, and may depend
on the type of editor used - for ex, I don't think you can use a
longer name with dumpster.
And again I don't see any reason behind all this...

[bond]

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ok good to know

the thing is that nero started using that space for writing
things like "2ch german audio", "6ch english audio" "english
director commentary" aso
now that nero used it that way, lots of parsers seem to pass
that info (of course nero itself, haali, videolan i think...)

[Jean Le Feuvre]

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now available in MP4Box (CVS):
* media language changing (-lang)
* initial media offset setting (-delay)

enjoy.

[bond]

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hm should it be possible to set the language while importing
(eg from .avi or .aac) or is setting the language only supposed
to work on existing files?

i ask because it doesnt seem to be possible to change the
language for the bifs/od streams with the following
commandline (i get a "bad parameter" error):
MP4Box -lang 2=ger -add input.mp4 -new output.mp4
with bifs having the id=2 in the input.mp4

when doing the following it works:
MP4Box -lang 2=ger input.mp4 -out output.mp4

[Jean Le Feuvre]

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This is now available on CVS, syntax is:
MP4Box -add file.mp3;lang=eng res.mp4

Note that you should never use "-add file.mp4" unless you
really need to, this option will erase all systems tracks
present in input file. If you just need a different output file then
use -out option...

[bond]

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ok nice

some questions:
1) how is the syntax when i want to import a .mp4 via -add
with more tracks and i want to set the language on all tracks
differently?
2) how is the syntax when i want to import an audio-
only .mp4 (still having bifs and od) via -add, as its most of the
time the case when muxing audio + video (eg from avi) to a
final .mp4?

[Jean Le Feuvre]

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1) you will have to import tracks one by one:
-add file.mp4#trackID=2;lang=fra

2) either
-add file.mp4#trackID=audio_ID
or
-add file.mp4

since by default all MPEG-4 systems tracks are removed
when importing media with -add.

[bond]

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ad 2)
of course i meant doing 2) and setting the language at the
same time

is it too necessary to set the trackid?