IPB

Welcome Guest ( Log In | Register )

 
Reply to this topicStart new topic
Detecting codec in a stream, aac adts vs mp3
stigc
post Oct 7 2012, 12:46
Post #1





Group: Members
Posts: 142
Joined: 13-December 04
Member No.: 18660



How does e.g. VLC detects the codec when opening a http stream?

Both AAC and MP3 has a very short sync mark which often appears in other streams.

http://www.flickr.com/photos/52807817@N00/4423485655/
http://www.mp3-tech.org/programmer/frame_header.html

This post has been edited by stigc: Oct 7 2012, 12:53
Go to the top of the page
+Quote Post
stigc
post Oct 7 2012, 13:07
Post #2





Group: Members
Posts: 142
Joined: 13-December 04
Member No.: 18660



I guess VLC parses the frame length number and sees if it matches the next sync mark?
Go to the top of the page
+Quote Post
benski
post Oct 7 2012, 18:38
Post #3


Winamp Developer


Group: Developer
Posts: 670
Joined: 17-July 05
From: Brooklyn, NY
Member No.: 23375



The first four bytes of an ADTS AAC frame header look exactly like an MPEG-1/2 "Layer 4" frame. So it's quite easy to detect the difference.
Go to the top of the page
+Quote Post

Reply to this topicStart new topic
1 User(s) are reading this topic (1 Guests and 0 Anonymous Users)
0 Members:

 



RSS Lo-Fi Version Time is now: 20th September 2014 - 05:59