[Mp4-tech] AAC header in MP4 file format

[Harisha V]

Hi 
The Decoder requires only the sampling frequency of the bitstream to decode. But in MPEG-4 file format for Audio is Mp4 where in raw AAC information is placed in AudioSpecificConfig structure .This header is transported via MPEG-4 systems. This contains AudioObject type (e.g AAC-LC ,AAC-Main etc). and sampling frequency index  and other information which are necessary for the decoding process and parsing of raw bitstreams .For more details refer ISO/IEC 14496-3:2001(E) part-3 subpart 1.
With Regards
Harisha 
-----Original Message-----
From: Shetty Ravindra [mailto:Ravindra.Shetty thomson.net] 
Sent: Wednesday, August 06, 2023 8:26 PM
To: 'Vinayaka Hegde'; 'Mody, Mihir'; 'bharat nihalani'; mp4-tech lists.mpegif.org
Subject: RE: [Mp4-tech] AAC header in MP4 file format
headder contains  the information
-----Original Message-----
From: Vinayaka Hegde [mailto:vinayaka.hegde celstream.com]
Sent: mercredi 6 août 2003 16:20
To: 'Mody, Mihir'; 'bharat nihalani'; mp4-tech lists.mpegif.org
Subject: RE: [Mp4-tech] AAC header in MP4 file format
Hi,
I think Mihir is right. But how can we identify input stream in RAW form is AAC or not? If decoder is know that, endoer is sending RAW form then only we can procede with decoding. 
If decoder is not aware of the input bitstream type and some encoder sends RAW form data to decoder. Is this possible?. If yes, How decoder identify that input is AAC RAW form? Is it mandatory to have MP4 header or MP2(ADIF/ADTS) header? 
Regards
Vinayaka
-----Original Message-----
From: Mody, Mihir [mailto:mihir ti.com]
Sent: Wednesday, August 06, 2023 7:26 PM
To: 'bharat nihalani'; mp4-tech lists.mpegif.org
Subject: RE: [Mp4-tech] AAC header in MP4 file format
HI Bharat,
The MP4 file contains AAC stream in RAW form. It is not possible to have ADIF/ADTS header in AAC stream of MP4 file
Regards,
Mihir Mody,
Multimedia Group,
Texas Instruments Inc.,
Bangalore, India,
Email: mihir ti.com
Phone :- +91-80-5099307
-----Original Message-----
From: bharat nihalani [mailto:ban611 yahoo.com]
Sent: Wednesday, August 06, 2023 6:56 PM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] AAC header in MP4 file format
Hi All,
What kind of header can a MP4 file have in case of AAC?
1) ADIF, 
2) ADTS, or
3) RAW. 
I found with the MP4 file format streams that I have, that the AAC stream was RAW, i.e. without ADIF or ADTS header in it. But is it possible to have ADIF or ADTS header present in the MP4 file in case of AAC stream?
Please clarify on this.
Regards,
Bharat
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