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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Hello Liwei,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Actually what I wanted to do is to change
the quantization parameter Qp just to see the effect of the requantization
error on the PSNR (like in the paper). I already managed to do that by
overwriting the rate control computation n the reference software.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks for your reply anyway.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Regards,<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Mohsen Shaaban<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<hr size=2 width="100%" align=center tabindex=-1>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span style='font-size:10.0pt;
font-family:Tahoma;font-weight:bold'>From:</span></font></b><font size=2
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma'>
x264-devel-bounce@videolan.org [mailto:x264-devel-bounce@videolan.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>jogging song<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, November 17, 2006
8:08 AM<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">x264-devel@videolan.org</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> [x264-devel] Re: [Mohsen
Shaaban <mmm5554@cacs.louisiana.edu>] RE: Re: Using I-frame instead of
IDR</span></font><o:p></o:p></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Hi, Shaaban <o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'> I haven't caught what you said.<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>First, you want to transcode mpeg2 bitstram to h.264 bitstream.<br>
Second, the paper introduced an method which can reduce bit-rate of mpeg2
bitstream in frequency-domain,<br>
In the paper, the author just changed QP to do bit-rate
reduction and didn't use rate control. <br>
Third, you hope to see the effect of requantization error.<br>
Bitrate reduction will cause quality degrade which can be
expressed with PSNR.<br>
You mean you want to do bit-reduction with rate control?<br>
Best Regards. <br>
Liwei Song <br>
<br>
<o:p></o:p></span></font></p>
</div>
<div>
<p class=MsoNormal><span class=gmailquote><font size=3 face="Times New Roman"><span
style='font-size:12.0pt'>On 11/17/06, <b><span style='font-weight:bold'>Lists
administration</span></b> <<a href="mailto:videolan@lists.videolan.org">videolan@lists.videolan.org</a>>
wrote:</span></font></span> <o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'>----- Forwarded message
from Mohsen Shaaban <<a href="mailto:mmm5554@cacs.louisiana.edu">mmm5554@cacs.louisiana.edu
</a>> -----<br>
<br>
From: Mohsen Shaaban <<a href="mailto:mmm5554@cacs.louisiana.edu">mmm5554@cacs.louisiana.edu</a>><br>
To: <a href="mailto:x264-devel@videolan.org">x264-devel@videolan.org</a><br>
Subject: RE: [x264-devel] Re: Using I-frame instead of IDR <br>
Date: Thu, 16 Nov 2006 12:51:31 -0600<br>
X-Mailer: Microsoft Office Outlook 11<br>
<br>
<br>
The deleted attachment is at:<br>
<<a
href="http://lists.videolan.org/attachs/20061117/frequency-domain.pdf">http://lists.videolan.org/attachs/20061117/frequency-domain.pdf
</a>><br>
<br>
<br>
Hello Loren,<br>
<br>
First, I'm a member of x264-devel but I do not know how to post questions<br>
from within the x264-devel mailing list. Can you please tell me how to do<br>
that?<br>
<br>
Second, I have a question about H.264 transcoding from MPEG-2 bitstream, I<br>
hope you can help me.<br>
<br>
I want to do some experiments on the MPEG-2 bitstream before Transcoding, so<br>
I want to see the effect of requantization error on the stream and I read in <br>
one paper that you can do that by having a fixed triplet quantization<br>
scaling (fixed scaling value Qi, Qp, Qb) and my question is there any<br>
feature in MPEG-2 TM5 reference software that you can change to do that or <br>
one have to change the rate control algorithm in there?<br>
<br>
I attaching the paper for your reference (experiment shows in fig. 3 in the<br>
paper)<br>
<br>
I hope you have an answer or a guide for me to follow.<br>
I appreciate it and thank you. <br>
<br>
Mohsen Shaaban<br>
PhD Student in Computer Engineering<br>
The Center for Advanced Computer Studies<br>
<st1:PlaceType w:st="on">University</st1:PlaceType> of <st1:PlaceName w:st="on">Louisiana</st1:PlaceName>
at <st1:City w:st="on"><st1:place w:st="on">Lafayette</st1:place></st1:City><br>
<br>
-----Original Message-----<br>
From: <a href="mailto:x264-devel-bounce@videolan.org">x264-devel-bounce@videolan.org</a>
[mailto:<a href="mailto:x264-devel-bounce@videolan.org">x264-devel-bounce@videolan.org</a>]<br>
On Behalf Of Loren Merritt<br>
Sent: Wednesday, November 15, 2006 10:42 PM<br>
To: <a href="mailto:x264-devel@videolan.org">x264-devel@videolan.org</a><br>
Subject: [x264-devel] Re: Using I-frame instead of IDR<br>
<br>
On Wed, 15 Nov 2006, Axel Gunter wrote:<br>
> Loren Merritt wrote:<br>
>> On Wed, 15 Nov 2006, Axel Gunter wrote:<br>
>> <br>
>>> I noticed all the I-frames introduced by the x264 code were IDR
Access<br>
>>> Units. Is there a way I can have non-IDR I-frames in x264
encoding?<br>
>><br>
>> No. Why do you want non-IDR I-frames? The only reason I can think of
is <br>
>> open-GOP B-frames, which x264 also doesn't do.<br>
><br>
> I guess the compression would be better if the frames following the IDR or<br>
<br>
> I-picture could use frames temporally before the IDR/I-picture since they <br>
> have more reference frames to chose from. Since IDR forces a decoder<br>
> reference buffer flush, this isn't possible. Correct me if I am wrong.<br>
<br>
In that case, look at --min-keyint. If a scenecut is too close to the <br>
previous IDR (default: 25 frames) it gets encoded as a non-IDR I-frame.<br>
Note that this is not optimal, but the metric that would really optimize<br>
for compression ratio isn't possible to measure in 1 pass, and I haven't <br>
written a 2 pass scenecut/IDR algorithm yet.<br>
<br>
--Loren Merritt<br>
<br>
--<br>
This is the x264-devel mailing-list<br>
To unsubscribe, go to: <a href="http://developers.videolan.org/lists.html">http://developers.videolan.org/lists.html
</a><br>
<br>
<br>
----- End forwarded message -----<br>
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