[NUT-devel] Re: r19110 - trunk/DOCS/tech/nut.txt

[Måns Rullgård]

Rich Felker <dalias at aerifal.cx> writes:

> On Mon, Jul 17, 2006 at 12:10:56AM +0100, Måns Rullgård wrote:
>> Baptiste Coudurier <baptiste.coudurier at smartjog.com> writes:
>> 
>> > aac cant be stored as adts in nut it violates the specs (double
>> > container)
>> 
>> ADTS is IMHO no more of a container than mp3 is.
>
> I really don't know what ADTS looks like, but I would say that if it
> doesn't multiplex streams and doesn't have timestamps or seek info,
> it's probably not a container..

The ADTS header is 7 bytes per frame containing a sync word, AAC type,
sample rate, number of channels, frame size, and a few useless pieces
of information.  It is equivalent to the mp3 frame header.  In a
container with proper framing, this information can be stored in a
global header instead.  MOV does just that, but of course uses a
different format for the global header.  See libavcodec/parser.c and
libavformat/adtsenc.c for the gory details.

The reason ADTS exists is (I assume) to make possible raw AAC streams
and headerless streams for broadcast.

> However if it's stupid bloat it probably shouldn't be stored in NUT
> anyway.

Since nut has an extradata space, using it seems like the right
choice.  It does save a little overhead.

-- 
Måns Rullgård
mru at inprovide.com