[Mp4-tech] IDR period and intra period

[Venkat Subbiah]

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

 

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From: mp4-tech-bounces lists.mpegif.org
[mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of ashfiqua tahseen
Sent: Friday, March 14, 2008 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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