Welcome to Doom9's Forum, THE in-place to be for everyone interested in DVD conversion.

Before you start posting please read the forum rules. By posting to this forum you agree to abide by the rules.

 

Go Back   Doom9's Forum > Video Encoding > New and alternative video codecs

Reply
 
Thread Tools Search this Thread Display Modes
Old 26th October 2005, 16:27   #1  |  Link
noam_korem
Registered User
 
Join Date: Oct 2005
Location: Israel
Posts: 9
WMV9 bidirectional frames performance

I've been playing around with several WMV encoders (including one from MS), and it seems like this standard exhibits low performance concerning B-frames.

While MPEG4's use of B frames usually reduce bitstream size by 10-20% (in relation to P-only streams), the WMV standard rarely shows any reduction at all (!).

The encoders I checked supported 1-7 consecutive B frames, 4MV, AC prediction, and all the knacks and gadgets available in the standard. It simply seems like WMV B frames are not cheap enough, while distancing the P-vops from one another demands a large amount of bits...

Can anyone comment on this? I'd like to know if this phenomenon is familiar, or am I doing something wrong?

NK.
noam_korem is offline   Reply With Quote
Old 26th October 2005, 16:30   #2  |  Link
IvS
.
 
Join Date: Sep 2002
Posts: 139
What encoders have you tested?
Maybe the bitstream is already pretty optimized and therefore there's not much reduction? (Not sure, just a thought)
IvS is offline   Reply With Quote
Old 26th October 2005, 17:50   #3  |  Link
noam_korem
Registered User
 
Join Date: Oct 2005
Location: Israel
Posts: 9
Used a microsoft encoder, amongst others.

This issue has appeared across several encoders, which leads me to think it is not encoder related.

My feeling is that there seems to be inherent issues with the Bidirectional frame in the wmv standard.
MPEG4 uses 1 bit for SKIPed macroblocks in P frames, and 0 bits for NOT_CODED macroblocks in B frames. This results in bit reduction when presenting the B frame feature into quiet scenes.
WMV uses 1 bit for SKIP in P frames, and 2 (!) bits for DIRECT SKIP in B frames.

NK
noam_korem is offline   Reply With Quote
Old 26th October 2005, 18:47   #4  |  Link
IvS
.
 
Join Date: Sep 2002
Posts: 139
Interesting
It would be interesting to know whether this is really a format limitation or encoder limitation.
Also, I had no idea there are third party WMV9 encoders, front-ends - sure. If you could say which you've used I'd be interested in testing them myself.
IvS is offline   Reply With Quote
Old 26th October 2005, 20:04   #5  |  Link
bond
Registered User
 
Join Date: Nov 2001
Posts: 9,770
what other encoders? afaik m$ is the only one providing a vc-1 codec atm
__________________
Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau)
I know, that I know nothing (Socrates)

MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide)
Ogg Theora | Ogg Vorbis
use WM9 today and get Micro$oft controlling the A/V market tomorrow for free
bond is offline   Reply With Quote
Old 26th October 2005, 22:26   #6  |  Link
lazyn00b
Registered User
 
Join Date: Feb 2003
Location: USA
Posts: 152
Quote:
Originally Posted by bond
what other encoders? afaik m$ is the only one providing a vc-1 codec atm
Actually, there are tons of VC-1 implementations out there (Google is your friend!) - the bad news is that they are all insanely expensive. Take this one for example:

http://www.inlethd.com/products/fathom.htm

I think it costs about $25,000! Supposedly the quality of this software/hardware-assisted solution is much better than the "stock" encoder provided by Microsoft, and you can encode HD video in real-time.
lazyn00b is offline   Reply With Quote
Old 26th October 2005, 22:51   #7  |  Link
bond
Registered User
 
Join Date: Nov 2001
Posts: 9,770
i assume these are all the same implementations: the one from m$
__________________
Between the weak and the strong one it is the freedom which oppresses and the law that liberates (Jean Jacques Rousseau)
I know, that I know nothing (Socrates)

MPEG-4 ASP FAQ | AVC/H.264 FAQ | AAC FAQ | MP4 FAQ | MP4Menu stores DVD Menus in MP4 (guide)
Ogg Theora | Ogg Vorbis
use WM9 today and get Micro$oft controlling the A/V market tomorrow for free
bond is offline   Reply With Quote
Old 26th October 2005, 23:33   #8  |  Link
IvS
.
 
Join Date: Sep 2002
Posts: 139
lazyn00b: Heh, yeah, that's a bit expensive.
I wanted to download the trial software to test if it indeed gives similar results to Microsoft's implementation, but got "Coming Soon" .
IvS is offline   Reply With Quote
Old 30th October 2005, 08:23   #9  |  Link
noam_korem
Registered User
 
Join Date: Oct 2005
Location: Israel
Posts: 9
My guess that this phenomenon will be present also in the VC-1 codec. So if anyone has got a VC1 encoder out there, I'd be happy to hear about its' performance as well

NK
noam_korem is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT +1. The time now is 11:07.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.