[openbeos] Re: Implementing MP4
- From: Philippe Houdoin <philippe.houdoin@xxxxxxx>
- To: openbeos@xxxxxxxxxxxxx
- Date: Tue, 05 Jul 2005 10:46:35 +0200
David McPaul asked:
> I am trying to decide on the best way to implement an MP4 reader.
>
> Basically the MP4 format is based on the Quicktime format so my
> current quicktime parser seems to read them ok, but there are some
> differences and I am concerned that there might be differences that
> would make it difficult to have 1 parser handling both formats.
>
> But the real question is. Should I be creating a new FAMILY type
> and associated functions to support it.
>
> Currently we have:
>
> typedef enum {
> B_ANY_FORMAT_FAMILY = 0,
> B_BEOS_FORMAT_FAMILY = 1,
> B_QUICKTIME_FORMAT_FAMILY = 2, /* QuickTime is a registered
> trademark of Apple Computer */
> B_AVI_FORMAT_FAMILY = 3,
> B_ASF_FORMAT_FAMILY = 4,
> B_MPEG_FORMAT_FAMILY = 5,
> B_WAV_FORMAT_FAMILY = 6,
> B_AIFF_FORMAT_FAMILY = 7,
> B_AVR_FORMAT_FAMILY = 8,
> B_MISC_FORMAT_FAMILY = 99999,
> } media_format_family;
>
> So I was thinking of creating a B_MPEG4_FORMAT_FAMILY = 9,
> the associated structs and add them to the unions and
> GetMP4FormatFor etc?
Can't B_MPEG_FORMAT_FAMILY be reused there?
I dunno how much MPEG4 differ from MPEG2 & MPEG1, but at least they all share
the same MPEG format family links, right?
If it's necessary, maybe the current Haiku's mpeg format relative struct(s)
could be adjusted to support MPEG1, MPEG2, MPEG3 *and* MPEG4 *without* breaking
ABI?
> How do I make sure we don't lose R5 compatability with this?
With a new B_MPEG4_FORMAT_FAMILY, that would be hard. But, as R5 never had a
MPEG4 reader thru MediaKit anyway, it would only break those apps that expect a
format family type in the known range at their compilation time. Which is wrong
and prevent them from supporting any new media family(ies) in the future...
Anyway, I would rather like, if you can't reused one of the known format family
types, that you follow the same path than the several media readers already
using B_MISC_FORMAT_FAMILY instead:
OGG
Matroska
AU/SND
MusePack
AIFF
> Or should I just use the quicktime family?
Even if it sounds weird (semantically) that a MPEG4 reader report being of
QuickTime formats family instead of MPEG's one, if it's really easier because,
well, (technically) MPEG4 comes from Qt, go for it.
Maybe this media format family enumeration should go dynamic in a future > R1
media kit?
- Philippe
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