[Mp4-tech] IDR period and intra period

[Ye-Kui.Wang nokia.com]

An important typo below:
IDR is a subset (NOT superset) of Intra. 
BR, YK
________________________________
	From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ext Satendra
	Sent: Tuesday, March 18, 2024 11:11 AM
	To: Venkat Subbiah
	Cc: ashfiqua tahseen; mp4-tech lists.mpegif.org
	Subject: Re: [Mp4-tech] IDR period and intra period
	Simple terminology 
	IDR picture is a superset of Intra picture.
	IDR picture is an Intra picture, but it says that now onwards
decoder can not use any of the previously decoded pictures as reference
picture for inter decoding.
	Best Regards
	Satendra
	On Mon, Mar 17, 2024 at 10:43 PM, Venkat Subbiah
<vsubbiah iavior.com> wrote:
		1.	What is the difference between an IDR picture
and Intra picture? 
		instantaneous decoding refresh (IDR) picture: A coded
picture in which all slices are I or SI slices that
		causes the decoding process to mark all reference
pictures as "unused for reference" immediately after
		decoding the IDR picture. After the decoding of an IDR
picture all following coded pictures in decoding order
		can be decoded without inter prediction from any picture
decoded prior to the IDR picture. The first picture of
		each coded video sequence is an IDR picture.
		Above is the definition of an IDR picture from the
standard. As you can see the focus of the definition is on "all picture
all following coded pictures in decoding order
		can be decoded without inter prediction from any picture
decoded prior to the IDR picture". This part might not be necessarily
true for just an I picture. 
		I slice: A slice that is not an SI slice that is decoded
using prediction only from decoded samples within the
		same slice.
		*       Above again is a definition from the standard
and as it reads the only restriction about I slice is the prediction is
only from decoded samples within the same slice. And it does *not* say
anything about following picture.
		-Venkat
________________________________
		From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ashfiqua tahseen
		Sent: Friday, March 14, 2024 12:17 PM
		To: mp4-tech lists.mpegif.org
		Subject: [Mp4-tech] IDR period and intra period
		Hi,
		1. What is the difference between an IDR picture and
Intra picture? And what is the difference between IDR period and intra
period?
		2. We can set different QP for I and P slice. I am just
curious, in real application, do the companies use different QP for
tham?
		Any suggestion will be highly appreciated.
		With regards,
		Ashfiqua
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