Re: [Helix-client-dev] X-MP3-DRAFT-00

The ADU descriptor is not part of the ADU Frame. It is a part of the
RFC 3119/5219 packet payload which precedes each complete or partial
ADU frame.

An ADU frame is an independently decodable and playable frame, which
consists of the MPEG audio header and side_info, followed by the audio
data associated with that header and side info.

http://tools.ietf.org/html/rfc5219#section-4.1

For layers 1 and 2 the ADU frame is identical to the MPEG audio frame,
but for layer 3 (MP3) that is not the case, which is the reason we
needed the DRAFT-00 format and eventual RFC 3119, rather than just
using 2250 for MP3!

-Jamie

On 03/30/2012 03:17 PM, Robert Craig wrote:
> Thanks Jamie. That helps.
>
> When I view the RTP stream in WireShark, I don't see any ADU descriptor
> (i.e. one or two-byte header), so I am wondering why people call it an
> "ADU" frame. I just see the standard MP3 32-bit header at the start of
> each packet.
>
> -- Rob Craig
>
> Jamie Gordon wrote:
>
>>  The is no definitive specification. :)
>
>>  The packet payload is simply one complete ADU frame (no payload
>
>>  headers). RTP clock rate is equal to audio sampling rate. Marker bit is
>
>>  unused.
>
>>  The definition of an ADU frame can be found in RFC 3119.
>
>>  Thanks,
>
>>  Jamie
>
> On 03/30/2012 11:53 AM, Robert Craig wrote:
>
>>/Can anyone post details on the MP3 via RTSP packet format that Helix/
>
>>/uses. It's called X-MP3-DRAFT-00, but I can't find a definitive/
>
>>/description of this format anywhere on the Web, just a few off-hand
> remarks./
>
>>//
>
>>/Thanks!/
>
>>//
>
>>/Rob Craig/
>
>>
>