[x264-devel] Doubts about structure H.264/AVC

[Narasimhan Mandayam-MGI1318]

Bruno,
 
 It looks like you have listed the bytes captured somewhere in the
middle of a stream as the video payload bytes 00 00 01 41 indicate what
Gary has listed. MPEG-2 transport requires the byte-stream format for
NAL units and hence the 00 00 01 preceding the NAL header. However,
MPEG-2 transport also requires the use of access unit delimiter NAL unit
to start all pictures (nal type 9). 
 
 There is no term called 'elementary stream header' - an elementary
stream is concatenation of access units in byte stream format and each
access unit must obey the rules listed in section 7.4.1.2.3. If your
capture is at the beginning of the video sequence, then the access unit
MUST be an Idr (nal type 5) and preceded typically by an access unit
delimiter, SPS, any SEI and PPS.
 
Regards
Sam Narasimhan  

________________________________

From: Gary Sullivan [mailto:garysull at windows.microsoft.com] 
Sent: Wednesday, December 12, 2007 1:00 PM
To: Bruno Guedes; ohm at ient.rwth-aachen.de; Luthra Ajay-MGI1164;
x264-devel at videolan.org
Cc: Narasimhan Mandayam-MGI1318
Subject: RE: Doubts about structure H.264/AVC


This question seems like mostly an MPEG-2 TS question rather than an
H.264/AVC question, and so it is likely to be outside of my primary area
of expertise.
 
It does seem possible that the 41 could be a NAL unit header, containing
a coded slice (nal_unit_type = 1) of a reference picture (nal_ref_idc =
2).  But that would not be what you would expect to find at the start of
a new bitstream, since it is not an IDR slice and it is not an SPS or
PPS or SEI or AUD or such thing that would be found at that location.
 
Adding Sam for MPEG-2 TS expertise.
 
Best Regards,
 
Gary


________________________________

	From: Bruno Guedes [mailto:brguedes at gmail.com] 
	Sent: Wednesday, December 12, 2007 7:00 AM
	To: ohm at ient.rwth-aachen.de; aluthra at motorola.com; Gary
Sullivan; x264-devel at videolan.org
	Subject: Doubts about structure H.264/AVC
	
	
	Hi,
	I'm a IST-student and I'm starting to work in IPTV area. I use
the VLC streamer and I want to transmit H.264/AVC over RTP/UDP in TS
(transport stream) mode!
	I analyze the bytes in reception with wireshark, but I got
something like this: 
	"00 00 01 e0 17 93 80 c0 0a 31 29 0d 9a 6b 11 29 0d 9a 6b 00 00
01 41 9a 5d 2e b2 08 7f fc db 08..."
	As I could understand the first nineteen bytes are PES header. I
think (but I don't have sure) that the byte 41 (that is ahead of the
start code (00 00 01)) is the NAL header! But I don't know where is the
elementary stream header! 
	If someone can explain me what's wrong with my thought or
where's the elementary stream header, I appreciate.
	
	best regards
	
	-- 
	Bruno Guedes 

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